| Author | Message | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 24 Registered: 11-2008 Posted From: 76.64.241.32  Rating: |
All you guys that were kind enough to help me with my ‘high temp, low oil’ alarm problem (under thread: ‘Revisiting the 'Hard to Start 8-71 ...’), thanks much! I will get back to that shortly, but I promised an update on that ‘headlight’ matter after my electrician had a look (under thread ‘Headlamp Problems’). Well, now he’s had a look… a ten hour look, as it turned out. After four blown lamps yards of repaired / refreshed wiring and voltmeter tests just about everywhere, I have head lights. Whew! But for how long? (For those not familiar with my particular rig, it’s an MCI -5C, vintage of 1977) Here’s a full report (without all the boring diagnostic details): First, my electrician – fellow named Robert Booth – says he’ never seen anything like my weird setup. And this guy is super experienced… he works mainly on trucks and heavy (VERY heavy) equipment, much of which is powered by 24V. I have (always have had, as it turns out) 12V lamps on the’ ’outside’ (the low beams) and 24V lamps on the ’inside’ (the high beams). Which explains why my lovely new 12V high beam halogens turned into flashbulbs when I clicked on the brights – the 24v (28V actually) surge instantly fried the 12V filaments. Now things get a tad more technical (and way over my head), but here goes: Normally, one would expect to find two power leads to each pair of lamps, and a common ground. But in my case, there are two grounds (per pair of lights) and ONE power lead (wire). One ground is what you’d normally expect (a simple ground), but the other (the second ground) loops back through a resistor and a ‘module’ and two (redundant) breakers… the latter apparently set up to prevent loss of lights in event of overload. This ‘module’ and resistor knock down the 24V input to 12V. But for whatever reason, this only works on the ‘outside’ (low beam) lamps. Soooo…. When I dim the lights, the inside lamps (the ‘brights’) do not completely extinguish. They remain on, but just barely, like a set of marker lights. Makes sense (I guess) because 12V power is circulating through them (to power the 12V ‘outside’ low beams). The 12 volts keeps the ‘brights’ lit, but not enough to illuminate anything. When I hit the ‘bright’ switch, the outside lamps (the 12V low beams) go ‘up’ – raise their elevation of beam – and the inside lamps fully illuminate. So on ‘bright’ I have four lamps fully illuminated. Now I could – and may temporarily do – put 12V lamps in all the pods and just run exclusively on low beams. I’d have to remember not to hit the ‘brights’ but I’d have four fully illuminated lamps. Okay, they’d be pointed somewhat downward, but it would be plenty of light for my purposes (I don’t intend to travel on dark and curvy little mountain roads… I have my car for that kind of stuff). But Robert Booth’s suggestion will probably be my ultimate solution: Just change the entire system back to what it originally was… a straight 24 volt system. (Reminds me of my latest song, ‘Back to Where I’ve Never Been.) The biggest drawback to Robert’s suggestion is that nobody makes a 24V halogen. Plus, 24V headlamps are hard to find and twice the price of the 12V version. Then again, how often does on need to replace headlamps? (Except, of course, for moi…. having just gone through four in two days). Somewhere down the line, my bus was jury–rigged (or is it ‘jerry-rigged – I’ve always wondered) to use 12V headlights. It was a job poorly done and only 50% successful. But, for the time being, I guess I’m stuck with it. Has anyone had any similar experiences? Does anyone have any suggestions? Happy trails to all! Nellie Wilson | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 679 Registered: 7-2006 Posted From: 72.146.77.140  Rating: N/A |
My head hurts. Why don't you just buy a 24 vdc to 12 vdc converter, use 12 vdc headlights, and call it a day? We had a guy we called "Hurl Maggot". Everyone thought we called him that, because we thought he sounded like that famous country western singer... But no.... We called him that, because he had real bad breath. | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 26 Registered: 11-2008 Posted From: 76.64.241.32 Rating: N/A |
Hey, John - Makes my head hurt too. But have you checked out the previous 'Headlight Problem' thread? Were it so easy as you suggest, why the need for all these incredibly complicated schematics, requiring all these incredibly expensive parts? Forty - yes, 40 replacement parts. And that's per MCI Service Bulletin #1930 (thanks again, Don) Even the more simplistic, less complicated approach offered by George (and supplied by Ian) isn't all that simple... at least not to my little pea brain. But don't get me wrong, John... I'd love to apply your solution to my problem. But tell me, just where exactly would I hook this converter into the system? You know, without affecting all the other ESSENTIAL 24V components. And which breakers and fuses, etc. would need to be retrofitted to accomodate the different voltage? And what wiring would have to be upgraded to handle the increased amperage of the 12V charge? You see, to me. it ain't all that simple. But I LOVE ya for your concern! Nellie Wison | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 680 Registered: 7-2006 Posted From: 72.146.77.140 Rating: N/A |
Loveya' too, man. But uhhh.... In updated schematics for the MC9 (and as it were in my now sold MC9), the headlights are (had been) changed to 12vdc, and operated from a 24vdc to 12vdc converter. You can mount the converter in the battery compartment, and run the 12vdc lead to the panel, or the headlamps. You're going to substitute the 12vdc for the 24vdc -to the lights-. Center tapping is a baaa-aaad way to do it. It causes the batteries to be unbalanced, continually discharging only one of the two when the headlamps are on. That show pony is also in earlier manuals, for whatever reason MCI had to do that, at that time. Using a converter is simple, easy, and foolproof. You're only supplying the converted voltage to the headlamps (or whatever other bulbs you want to run on 12vdc). The batteries remain being charged as they normally are, and there's no maze of idiotic wiring to paw through on dark and rainy nights. Some guys ran their 12vdc lights from the "RV" side. If you're going to have 12vdc appliances and a 12vdc house system, just use that to power the lights. This really doesn't take a rocket surgeon to figure out. (what?) | ||
| Wec4104 (Wec4104)
Registered Member Username: Wec4104 Post Number: 7 Registered: 7-2008 Posted From: 68.46.66.57 Rating: N/A |
Just for argument's sake, what about the possibility of staying with 24V, but updating the headlight hardware? I am assuming that the current set-up has four 7" round sealed beam lamps. The issue is that Nellie can't find halogen sealed beams in 24V, and doesn't want to settle for the low performance of old style tungsten sealed beams. So why not update the headlight assembly to handle a smaller 24V halogen bulb (H4, 9004, or similar)? Hella and other companies offer the 7" round glass and reflector assembly to fit the existing form factor. I am talking about a conversion as discussed in the following link: http://www.garbee.net/~cabell/headlights.htm The result would give you ... - the best lighting performance - Simplified 24V wiring - Readily available (and easy to carry) spares | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1447 Registered: 12-2000 Posted From: 67.181.166.160 Rating: |
Nellie - I'm going to repost here my suggestion from the "Headlamp Problems" thread: "Another thought which comes to mind, and hasn't been mentioned yet, is to pick up a Vanner Equalizer (get one from Nick @ Nimco). One side ties into the 24v off the batteries, the other side gives you 12v for just about everything you need. Designed so that neither of the big 8Ds are drawn down by 12v more than the other. They're used quite extensively on transit buses, so Nick will have lots of used ones available. They're also pretty dependable, rarely do you hear of problems with them, provided they're wired correctly. As with anything else electrical, if you don't do it right, you'll let the smoke out! " If you used one of these, then you could easily run 12v headlamps. And I'm sure Robert could easily figure out how to wire it into your coach's electrical system for you. Not only could this power your headlamps, but also any other 12vdc stuff you'd like to run - radio, gps, cb, etc. FWIW & HTH. . .  | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 160 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
"Center tapping is a baaa-aaad way to do it. It causes the batteries to be unbalanced, continually discharging only one of the two when the headlamps are on." If the headlamps are wired in series with what MCI calls a balance lead (center tap) the only time the system would draw unbalance current from one battery is if there is a bulb failure and you continue to use the headlamps. With this system a failure of one item is less likely to give you an all lights out situation. If you use a 24-12 Volt converter and it fails you have no lights. Wish someone with a MCI 5 schematic would post the headlamp circuit. All or most of the wiring and parts should be there with the exception of the balance lead and maybe a couple headlamp relays (cheap). They just need to be rearranged to use 12 Volt bulbs. Nellie, not sure how you can mix 12 and 24 volt lamps since dual headlamp systems normally use one duplex lamp per side, that is a lamp with both a high beam and low beam element in the same lamp, and the other lamp on that side is usually a single element lamp, high beam only. Apparently yours have been rewired to only use one bulb for each beam, that is one lamp for low and one for high on each side. Wish you were close so I could help you fix this. Headlights are important when you need them. Good luck Don 4107 | ||
| David Dulmage (Daved)
Registered Member Username: Daved Post Number: 224 Registered: 12-2003 Posted From: 142.46.199.30 Rating: N/A |
That's strange. However the MCI modification as described on the other post on this forum does work well. FWIW DaveD | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 627 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Nellie, Don said it right the first time, now he's done it again! Got my vote too! Sorry to say this, but if it took the guy 10 hours to do what you posted, with NO repairs, he's no electrician, and you got had. Me and John go way back, but he made a mistake in his last post, my schematic, which is a simplification of MCI's drawing, WILL NOT BURN WATER OUT OF EITHER BATTERY, PERIOD!!!!! (Neither will MCI'S.) BW !CORRECTLY! explained the current flow thru MCI's circuit in his reply to your first post on this subject. What I suggest is to follow the wire from the bus hot thru the master, the dimmer switch in whatever position you choose, and the headlight(s) on that side. Note that the "ground" wires on that side are connected to the equalizing wire, which is connected to the negative terminal of the ungrounded battery. Now, follow the connection from the positive of the grounded battery, (which just happens to be the equalizer wire) thru the 24 Volt relay that is added, thru the headlight(s) on the other side, and to chassis ground. After a while, it will sink in that each battery runs the headlights on one side only, thus the current draw out of each battery is equal. And, if you want to get really picky, BW was and IS right, with the engine running and the lights on, no headlight current flows thru either battery, it ALL goes thru the headlights. If one burns out, the other stays lit, and still no unwanted current flow because of the equalizer wire. In my comments on your previous post on this subject, please note the part reading "you can't run two 12V low/hi beam headlights in series on 24V and have them work properly, because they have only one ground for the two filaments." Obviously this is part of what your previous owner tried to do. There are several of us here who can apply my drawing to your bus, and have 12V halogen bulbs operating properly, IN THREE HOURS! As I said before, you need an ELECTRICIAN. George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1448 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George, Don, Nellie & others - I was doing some computer clean-up work on my picture files last night and came across this schematic for 12vdc headlamps on a 24vdc system. Would appreciate your comments.  FWIW & HTH. . . | ||
| Wec4104 (Wec4104)
Registered Member Username: Wec4104 Post Number: 8 Registered: 7-2008 Posted From: 68.46.66.57 Rating: N/A |
RJ's circuits look workable to me. My only concern would be with the consequences of having a relay fail. Since the two relays are wired in series, if either one fails, both lights go dark. It is not that much of a concern on the high beams, but could be on the low beams. It wouldn't be much fun to be twisting around some back roads at 10pm and suddenly have no lights. If going with that design I would use high quality relays and be absolutely sure of all wiring connections. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 161 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
RJ, It depends on how the 12V is derived. If it is from a 12-24V converter or a Vanner or a house bank that is 12V it will work. If the 12V source is a center tap from the batteries you have a unbalanced battery bank and much use can damage the batteries. The converter or Vanner are maybe a little less reliable than following George's diagram in that if the converter or Vanner dies you are left without any headlights. If you have a lamp burn out there is no risk to the batteries from being unbalanced. If you follow George's plan any one part failing is not going to leave you without any headlights. However with the center tapped system if you run for an extended period with a headlamp out you are unbalanced and can damage the batteries. As they say, you pays your money and you takes your chances. Good luck Don 4107 | ||
| Les McDaniel (Rainbow)
Registered Member Username: Rainbow Post Number: 7 Registered: 2-2007 Posted From: 75.157.92.103 Rating: N/A |
Nellie Use your Vanner equalizer or 12V house system to supply 12V to the headlight switch and wire the lights like all normal N.A. vehicles. As for the ten hours to sort the system out. When you have know idea how it was intended to work the time seems reasonable. | ||
| Jerry campbell (Busin704)
Registered Member Username: Busin704 Post Number: 9 Registered: 8-2008 Posted From: 71.28.108.35 Rating: N/A |
Guys On my 102A3 the head lights are run on a center tap from MCI this is a 1986 | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 628 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
RJ, I would echo Wec's comments on relays in series, and Don's on the source of the 12V supply. Don, Thanks for the comments, understanding, and support. Les, Please read Nellie's prior post on "Headlight problems," and all of the replies carefully. Please spend some time on the schematic that I provided, and realize that it has been viewed by everyone on the board, and nobody wants to change it. I put a lot of thought into that schematic to make it SIMPLE, COST-EFFECTIVE, and SAFE! Please note all of the comments about "center tapping not being advisable," and explain how "Use your ... 12V house system to supply 12V to the headlight switch is not going to abuse the ungrounded battery in a 24V bus? (Nellie does NOT have a seperate 12V alternator to run her house batteries.) Ignoring the cost of a Vanner, it does produce heat while operating, so must be installed in a dry ventilated area, and cables run to it from EACH of the four battery terminals, and a 12V supply cable run to the front. Then the headlight switch wire moved from the 24V hot to the 12V hot. Change the headlights, and the high beam indicator bulb, and drive off, right? Back in the 18th century, a guy named Ohm firgured out that I=E/R. I is induced current measured in Amps, E is electromotive force measured in Volts, and R is the resistance measured in Ohms. Then a guy named Watt figured out that Watts, (the electrical unit of work) is amps times volts. W=AxV My schematic requires two 24V single-pole relays, two automatic resetting circuit breakers, and some wire, period. If I had really had my act together, it could have been drawn needing only one circuit breaker, but oh well. The entire right side headlight wiring is done by moving the ground wire from the chassis to the equalizer wire. The rest of the wiring changes are done in the front junction box of an MCI. Sorry to jump on a newbie, and just because I have over 600 more posts doesn't make me qualified, but. There is a whole lot of work put into that schematic to make it dependable, cost-effective, simple, AND WORK PROPERLY, which includes not abusing the un-grounded battery. Please tell us what is going to happen when Nellie turns on her new headlights after following either of your suggestions. (I've given you the information to figure it out.) IMNSHO, ten hours to figure out less than 15 individual wire runs, all of then color-coded and tagged, the longest run being less than 12 feet is way excessive. George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1453 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George, Don & Wec - Thanks for your comments, they're appreciated. I don't know where I got that schematic. As I said in my post, I was going thru some picture files on my computer and ran across it. Now, if we really want to screw Nellie up, shall we post the schematic for how GMC used 12v headlamps on their 24v systems?? I think I may have one somewhere. . . PS: Happy Turkey Day everyone!! | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 228 Registered: 10-2003 Posted From: 74.244.14.221  Rating: N/A |
The more I read this thread the more I appreciate having a 12 volt coach | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 629 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
RJ, Your comments are always appreciated too! AND your MC6 pictures! I read your comment about "found it and what do you think...?" and it would work. Its only drawbacks are the two 12V relay coils in series. If one fails, both lights go out. Then we don't know where the 12V supply comes from. If its a Vanner, its fine, if its one batt, its not. I'll bet you knew that before you posted it too. It would be better with 24V relays in parallel, as then there wouldn't be the chance of a double failure. I wonder if GM's schematic is any more complicated than MCI's? I don't get my turkey until after 6pm, when the girlfriend's kids get back from their in-laws, so here I am pulling wires. Regards, George | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1400 Registered: 12-2000 Posted From: 76.66.17.239 Rating: N/A |
Warning: balanced reporting required! As a public service announcement, I would like to offer this supportive word for the future researchers on this topic of centre tapping... and suspecting that there may be an unnecessary scare to those who have, or are contemplating, a certain style of 12V headlight wiring involving a certain dreaded wire to the middle of the 24V battery bank.... It will NOT be of long standing harm to your batteries, if you have the MCI style of wiring with a "balance" or "neutral" or "centre tap" wire, and you blow a headlight, and you drive all night, or maybe another night after that, with the one headlight imbalancing your 24V battery bank. Replace the headlight at your convenience and carry on. Taking 12 volts off the middle of a 24 volt battery bank only becomes a problem if you are doing it incessantly, constantly, and forever. The batteries will not notice the small assault on their sensibilities of a headlight for a night or two. We busnuts need a little context sometimes... happy coaching! buswarrior | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 685 Registered: 7-2006 Posted From: 74.230.106.67 Rating: N/A |
Great schematic, George! It's a decent way to rewire for 12vdc headlamps. The one thing I've noted through the years I've lurked on these type forums, is that the ability of the readers are very varied. While your rewiring project may seem easy to you (along with many others), there are probably an equal number of individuals that will feel the undertaking is much too complicated to do in any reasonable amount of time. Somehow, for some reason, the issue of component failure - as in a "Vanner equalizer", or a simple voltage converter - is a big problem. I guess the failure of the light switch itself, a defective breaker, or a damaged harness, simply escapes reasoning.... I've lost my lights on buses, trucks and cars. I've had engines quit, brakes fail, and tires blow out, in spite of intense pre-trip inspections. Crap happens. If a converter is used that surpasses the current it is to supply, a failure isn't any more likely with that, than the failure of the brakes. Soooo... it seemed to me, that simply using a converter to convert 24vdc to 12vdc, instead of the "center tap", and using all the same components (24v relays, etc) that presently exists, is the absolute easiest way to use 12 vdc headlights, without having to rewire the entire headlamp system. In MCI's schematics, note where the 12vdc is coming from, and the single wire that carries the 12vdc. Connecting the output of a 24 to 12 converter at that point, seems the way to go. I'm no electrician, and it's a wonder I ever passed an Extra Class Amateur radio exam.... I will admit readily, that I often overlook things that stare me in the face.... Where did I go awry with my assumption here? I'm curious, and always on the learning curve. Here's MCI's Schematic:  PS: Absolutely right, BW!! The only trouble is, guys somehow figure that adding the radio, and a few other neat 12v things, are OK too. Look at the mess in Nellie's system... | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 163 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
"I guess the failure of the light switch itself, a defective breaker, or a damaged harness, simply escapes reasoning.... " Of course it is true that the failure of some components can give you a total lights out situation no matter how you derive 12v from 24V: Bad headlight on off Switch. Bad dimmer switch. Bad wire. Bad connection/s. Bad breaker. Bad ground/s. Bad who knows what. If you you wire them according to MCI and/or George, things that cannot give you a lights out problem: Bad Vanner . Bad 24-12V converter. Anytime you can eliminate potential failure modes that is a good thing. I have zero experience with Vanners but since they are OEM bus gear I would think they are pretty good. If I had a 24V bus would I have/want a Vanner? U bettcha. Would I use it to power my headlights if they were converted to 12V? Nope. Why would I when it can be done without that possible failure mode. I have had less than stellar reliability of after market 24-12V converters and would not trust my headlights to one. Don 4107 | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 687 Registered: 7-2006 Posted From: 74.230.106.67 Rating: N/A |
I do find it interesting, that most commercial operators have either removed, or disconnected the Vanner Equalizer, due to operational problems. The converters were usually found operational in most all used buses found for sale. But that aside, my argument isn't against George's project, it's a good idea, and well worth doing. But for non-techies, and the electro-challenged, it'd be a whole lot simpler to either use the MCI center-tap, or a converter in place of it. We all see these multi-relay plans; if not for the headlights, they're for the taillights, or tow vehicle. Nice schematics for those that can understand schematics, but there are alternative ways to accomplish the desired end result. If it's easy to do, and works, it oughta' be presented. There. I said it, and I'm glad. (where's Two_dogs and those fans?) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 631 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
John, My schematic USES the MCI center tap, its just a whole lot simpler on purpose. MCI's is a complicated schematic, but look closely at it in the morning, and you will see that the right headlights are grounded, and power for them is fed thru the 12V cutoff relay from the center tap. The left headlights are fed 24V from the dimmer switch, etc, but their "grounds" are connected thru terminal 1 on the left hand stud block, thru term 28 in the front junction box, the headlamp switch, and the 12V cutoff relay back to the center tap, so they only see 12V. IMNSHO, its way too complicated, and probably ended up that way because somebody didn't want to make a new loom when they still had a couple of hundred old ones? Back in Nellie's first post on "Headlamp problems," BW said that "this circuit doesn't actually have any current flow thru the batteries..." I said he WAS and IS right then, he's still right, NOW. I mentioned semantics then, and its still important, because a center tapped headlight circuit, and using the grounded battery of a 24V system for 12V are two entirely different things! Stealing 12V for continuous use anywhere shouldn't be called center tapping, it should be called theft. Next to consider in the headlamp foibles, is cost. To purchase and properly install a 24 to 12 Volt converter, Vanner or otherwise, isn't cheap, it makes heat and has to be vented, takes four cables, one off each battery terminal, a fairly large wire up front, and then you still have to read the mfr's schematic to find what wire to take off an reconnect to feed 12V to the headlight switch. After someone who can't read a schematic has done that, he still has to answer the question I asked Les a couple of feet above. I'm not going to answer my own question yet, but I'll bet you figure out what I'm getting at when I mentioned the Wattage formula, and cutting the voltage in half! Obviously I don't favor a 12V converter for this application for a reason, and its not really because of the dreaded total headlight failure when the converter fails. Part of it is its cost, part of it is work to wire it, and part of it is the answer to the question. Then you mention operators are taking them out because of problems? Don an I are not conspiring off-board, we just happen to agree on this post... I appreciate your views, and you are better at stirring things up than I am, even though I feel that it is better to let sleeping dogs lie. By the way, WD-40 will keep the steel wool from rusting! KUTGW, George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1454 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George - "I wonder if GM's schematic is any more complicated than MCI's?" Check your email. I've sent you a scan from the 24vdc P8M4905 shop manual. | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 688 Registered: 7-2006 Posted From: 74.230.106.107 Rating: N/A |
George - Re 24v converter: "you mention operators are taking them out because of problems? " My comment was regarding the Vanner, not a converter. The Vanner equalizer in my MC9 was disconnected, and a 24/12 converter installed. The former owner said that three of his buses had trouble with the Vanner and they were best when removed. I heard that same story from a few bus ops... True or not? Dunno, but I wouldn't be bothered using one. I would sooner put my faith into a converter.... But that said.. Your schematic is easy enough to follow, and it appears nearly foolproof. And of course you're correct regarding the advantage of stripping all the old wiring from the head lamp system, and re-wiring the entire head lamp system in the manner you described. And..... My bus is gone, but if I still had it, and the same type of "Nellie's" problems were plaguing my bus, I would change it out; rewire it, and be done with it, once and for all! If that problem didn't exist, but one of my 12v batteries were continually dying on me, I'd use a converter instead of that center tap. Why rewire what doesn't need rewiring. In Nellie's case... well... After re-reading Nellie's posts, and what his electrical wizard's done for him... for HOW MANY HOURS? And his conclusion that it oughta' be back to 24v? well George... You're right! Tear out that blasted wiring, and re-wire the mess using your schematic. If Nel's guru can read a schematic, it should take him a couple hours at the most, to get it all worked out. Maybe an extra hour to run down the parts. But it'd be fixed, once and for all. Ahh..... did anyone mention using the new LED head lamp replacement bulbs, that will run 12 or 24? (There, that oughta' keep this topic alive, ehh?) | ||
| Les McDaniel (Rainbow)
Registered Member Username: Rainbow Post Number: 8 Registered: 2-2007 Posted From: 75.157.127.185 Rating: N/A |
George I never said there was anything wrong with your schematic, and I know how it works and how it is similar to the MCI service bulletin. I have the one dated June 1981.It's 12 pages long with a parts list of 113 pieces. Coaches having the convsion should have identifing name plates on the headlight housings and at the driver's switch as they are included in the kit. Nellie does have a Vanner and its connected, READ THE POST. If is a 12v house system, how are the batteries charged? 24V with the vanner. Nellies wiring sound like a mess and could be rewired back to stock or using your diagram. I run an 8ga.wire from the house batteries (12V) to the front junction panel where I install a circuit panel. This supplies the CB, radio/CD, GPS, back-up monitor and all the other toys we park on the dash. This is also the 12V source for the headlights.The following pertains to MC7. MC5, MC8 & MC9 should be the same.The headlight switch supplies 24V to the headlight relay and dimmer switch. The headlight relay normal closed supplies the low beam. The dimmer switch opens the the NC contacts and closes the NO contacts. The normal open closes to operates the high beam. This is the hard part. Remove the 24V wire from the relay line in and discard. Attach a 12V wire from your new 12V circuit panel to the line in on the headlight relay. Replace all the seal beams and high beam indicator with 12V. Your done. If it makes you feel better, your can change the circuit breaker to the high beam to 15Amp. The wiring is the same gauge as your car or pick-up.You don't need a bus mechanic to trouble shoot this for repairs. A small schematic showing the source of the 12V and it's the same as your car. Probably simpler. Yes, I know ohm's law. That was grade 8 high school. Side Note.If you were to convert the marker lights, you need to split them into 2 circuits to handle the amp draw. Have done many over the years with no problems. Installed my first vanner in 1989 and used them in all my conversions with never a problem. You disconnect them, ground first before welding on the coach. As for the newbie, that goes to you George. I've been doing auto wiring for 35 yrs, the last 20 exclusive to buses of all makes and years. I also owned my own coach conversion company for 16 years and did all the hands on work and designing. Your over 600 post does not impress me. I've probably read them all. Some are good. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 568 Registered: 10-2006 Posted From: 66.82.162.18 Rating: N/A |
Were working out the electrics for the VL , which requires 24V for start and DDec and 12 for everything else. A CONVERTER (not equalizer) came with the transit donor , that will provide 60A to the house/ std bus systems. As KISS , as I can get FF | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 183 Registered: 12-2000 Posted From: 71.99.25.84  Rating: |
The advantage to using the "series center tap" scheme is that the lamp circuit is still essentially 24 volts, thus the wire size is correct. If you just change everything to 12 volts, whatever the source, the wires may be too small for the load. Len | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 785 Registered: 11-2005 Posted From: 208.54.200.246 Rating: N/A |
Tim, I was thinking the exact same thing!! I have one 24v truck, that is enough for me! | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 633 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Les, You missed the whole point of this, which is to make a simple and dependable 12V headlight conversion THAT WON'T BURN WATER OUT OF THE UN-GROUNDED BATTERY, and won't cause a total headlight failure! We all have to have an on-off switch, a dimmer, breakers and connections. Beyond them, 12V outside headlights can't be wired in series because there aren't enough ground terminals on the bulbs, and the inside bulbs shouldn't be wired in series due to instant darkness when one fails. Instant darkness will occur also when a 24-12V converter fails. When you take 12V off of the connection between the batteries on a 24V bus, that much current is run thru the ungrounded battery, which over-charges it, boiling out water, and shortening its life. So, the manufacturers figured out how to run 12V headlights on 24V without abusing one battery. This is the "center tap" circuit, or whatever else you want to call it. This doesn't abuse one battery, doesn't depend on a converter, and the other light(s) stay on when one fails. You didn't answer the question I asked you, even though you said you understand Ohm's law. When you cut the voltage in a circuit in HALF, and require the same wattage output, you DOUBLE the current. So, as Len says correctly above, the wires may be too small for the load. Unless the headlight circuit breaker(s) were rated for over 200% of the normal load current, they will trip, leaving Nellie in the dark again. Before you rush to post back, look at the circuits for a while, and you will see that the headlight switch and factory circuit breakers now only feed one side, so the same amount of current still flows in the wires as before. The left side wires are by themselves, also doing only one side thru the relays, so they are the right size also. The "hard" part is making a suggestion that works! There is a reason the manufacturers didn't just hook one battery up to the headlights. I also doubt that any of your conversion customers knew why they had a chassis battery failure in a year or so, they just went out and bought a new one. The factory wire sized for 24V will probably carry the doubled amperage on 12V ok, but the voltage drop WILL increase, resulting in mediocre light, which I think was the reason for this post? G | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 691 Registered: 7-2006 Posted From: 72.146.79.42 Rating: N/A |
The only thing I fail to understand, is why there's so much concern about a converter failing. There isn't a motor vehicle on the road today, that has any sort of a redundancy system to provide headlights when a component of the power supply to that system fails. We drive our cars, trucks and vans, with no redundancy system. Those of us that drove (or drive) commercial buses or trucks, have done (or do so), without any redundancy system. If the fuse or breaker goes, we lose our lights. If the headlight switch fails, so do our lights. If the harness fails, so do our lights. Yet....... there remains so much concern about using a converter. Wazzup? If the entire system needs to be rewired, George's circuitry is great to use. It's been well thought out, and schematicsized (new word; pay attention). But.... If you're continually depleting one 12v battery of the two used in a 24v system, and it's been "center tapped", and your lights have been working, then there's no need for an intense rewiring (unless that's what turns yer masochistic groove). Just use a 24 to 12 converter, and feed the 12v into where the present 12v tap now feeds. The lights will continue to work as before, but you won't be replacing a battery every few months. BTDT. Man.... major mountains out of speed bumps... whew. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 635 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
John, You're right, every vehicle on the road has a headlight system with a bunch of components. There just isn't any other way. But, most of those vehicles are getting their power from the one and only 12V battery in the vehicle, and the headlights are wired in parallel, with the proper wire size and circuit breakers. Because the lights are wired in parallel, there is no instant darkness when one fails. The chances of the alternator AND the battery failing at the same time are pretty slim, so nobody driving a 12V vehicle worries about it because it hasn't happened to them. Wazzup? There are 31 posts on the "Headlamp problems" thread which started this, then everything on this part of the same discussion, and only ONE post to "use the 12V house system..." That did indeed provoke a reply from me, as you can see, and for a reason I explained. FF mentioned the KISS principle, (Keep It Simple Stupid) which really applies here. The less components, the less chance of failure. FF has no choice in his application, but he'll really be in instant darkness when and if his converter fails, unless he installs a 12V battery after the converter? Using my design, you have NO ADDED CHANCE of total failure, because the lights are not dependent on a converter that you don't have to buy either! Bulb goes out, other side stays on, relay quits, other side stays on, no under-sized wiring, or under-rated circuit breakers, and it doesn't abuse batteries. Two cheap relays, two cheap circuit breakers, some wire and you're done. You say "If you're continually depleting...and your lights have been working...no need for an intense rewiring...Just use [BUY & INSTALL] a 24 to 12 converter..." IMNSHO, thats more work, and much more money. Wazzup 2? Peruse my schematic for a while, and you will see that the entire right side is done completely by MOVING THE GROUND WIRES FROM GROUND TO THE EQUALIZER WIRE. The whole left side is done by moving the two left side hot wires from their present studs with the right side wires to a couple of the un-used terminals toward the bottom of the front junction box. Then you have to mount two small relays and breakers in or near said front junction box, and run several pieces of wire, each less than 2 feet long. The hardest part of this is running the equalizer, balance, neutral, center tap, or whatever you want to call it, from the front J box to the batteries. That would have to be done with a converter also. Wazzup 3? The bottom end of an open beer can. (Its after noon on the East coast!) Just as in the story about the dog having relations with the skunk, I'm going to have to quit before I get all I want, because I've gotten all I can stand! Regards, George | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 636 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
RJ, Thanks for the schematics, its nice that we don't have a limit on Kilobytes on emails. As you say, they appear to be the same, and they're not as complicated as MCI's. I'm not quite sure what they mean by the circle dot drawn in the hot bus bar labeled "Battery Junction" though, and I'm afraid to guess. Thanks again, George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1456 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George - This whole 24v/12v lighting thing isn't an issue with Fred's coach, as it's 12v anyway. Only uses 24v for starting the engine on this new Flxible he's playing with. His 4106, like mine, is all 12v. There is a difference between the two schematics I sent you. As I said in my note, one is for 24v headlamps, the other is for 12v headlamps with the rest of the coach being 24v. I'll have to look again at the circle dot thing. . . Glad you were able to read them, wasn't sure how they'd come across the wire! FWIW & HTH. . . | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 786 Registered: 11-2005 Posted From: 208.54.200.113 Rating: N/A |
Why do I get the impression that a bunch of you guys love to complicated things? You must be engineers!! If one battery dries out or discharges faster than the other simply switch batteries for a while. I doubt that two batteries ever deplete at exactly the same rate anyway. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 166 Registered: 1-2007 Posted From: 208.81.157.90 Rating: |
"If one battery dries out or discharges faster than the other simply switch batteries for a while. I doubt that two batteries ever deplete at exactly the same rate anyway." Running an unbalanced system does not just discharge one battery. It destroys by overcharging the other battery. The short version is: When you put a load on only one battery of a series pair the regulator averages the voltage of the pair. The regulator sees a reduced average voltage because of the load and tries to charge them up to normal voltage. Since only one battery was loaded the other battery gets overcharged. Over time it, the overcharged battery will suffer just like any other overcharged battery. When it suffers it's slow death it will take the other(s) with it. As has been amply pointed out, there are several ways of running 12V headlights on a 24 volt bus including just hooking up to the battery that is hooked to ground. The various benefits and pitfalls have been beaten to death. Just as with any other part of converting a bus choose what ever method floats your boat. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1403 Registered: 12-2000 Posted From: 76.68.123.169 Rating: N/A |
Me thinks this thread changed topic long ago. Headlights, and their voltage, have become a symptom, not the cause. Too bad we can't do that with physical illnesses? Smile, life's too short! happy coaching! buswarrior |
