| Author |
Message |
Matt (Hgtech)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 13, 2006 - 11:23 pm: | |
My batteries keep running dead on my Eagle after about 1 day. If use the battery disconnects - they are fine the next day. There is nothing I can find that is on the hot battery bus. So, here's my question. I've got a 3 wire factory alternator on the bus (for now). In the past, someone wired the "trigger" wire strait to the battery bus - so the alternator is always on is my understanding. Is the power pull on this "trigger" wire enough to kill the batteries when the bus isn't running? If this isn't it - i'm out of ideas . . .
Matt
1979 Silver Eagle Model 05 |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 5:36 am: | |
"Is the power pull on this "trigger" wire enough to kill the batteries when the bus isn't running?"
The Trigger wire is usually only given juice from the key switch on a car or with a relay on a coach.
A quickie cure would be to get Da Book and reqire as new.
A simple change would just be a relay that monitors the oil pressure , and allows the trigger juice only with pressure.
Seamless,
FAST FRED |
Pat Bartlett (Muddog16)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 7:41 am: | |
Some one told me I was crazy for stipping my bus down as far as I did, news for them, I already knew that! These buses, mine included are getting some age on them, it wouldn't take much of a short to drain batteries over nite. Electricity loves to make you look silly, the hardest thing to find is the component that isn't completely broken yet! Best way is to find a DC clampon ampmeter, they are not cheap, first thing would be to clamp onto your main positive wire and take an initial reading then go through your system one item at a time and isolate each and everyone. Watching the meter each and everytime! The other problem with these conversions is, how was it wired, where was it grounded, and what have I tied together that I shouldn't have! I've seen starters go to ground internally, I've seen battery cables bouncing on the chassis frame, look for the obvious. If all of the above doesn't work, find a good auto electric shop, and let them find it! Good luck!
Pat |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 8:16 am: | |
To expand on FF's good idea, use an oil pressure switch that has normally open contacts without any oil pressure and that close when there is oil pressure. You could install it in a "T" with the existing oil pressure switch. Then wire hot to one switch contact and on the the alternator from the other contact. As soon as you have oil pressure you will have excitation to the alternator. I had to do this on my Eagle also. Yes the trigger voltage will not only run the battery down but in some cases can damage the alternator if it is not turning.
Richard |
Matt (Hgtech)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 10:06 am: | |
I'm planning on moving to a smaller alternator that will be driven off the engine rather than the mitre box. It would be a single wire alternator to simplify things. Here's my question. Is a 100 Amp alternator enough. The only things that would be running off of it are: headlights, marker lights, tail lights, and dash gauges, and a small CB radio. Everything else will be running off the house system. I've got two 8D's right now and per your all's advice, I don't plan on changing that.
I'm pretty sure the alternator is the cause of the dead batteries. When I rewired the front electrical panel - I used two really large relays with control switches on the dash that serve as sub battery disconnects for the front electrical system. So I know the juice drain isn't coming from there. I haven't rewired the rear electrical box yet and thats where the alternator is triggered at right now.
Thanks!!!!
Matt
1979 Silver Eagle Model 05 |
Gary Stadler (Boogiethecat)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 10:51 am: | |
An interesting way to find a voltage leak, if you have access to the wires:
Take a 4-1/2 digit DVM, measure and note the voltage at your battery,down to the millivolt, with a long ground wire (like as long as your bus) hooked from the battery negative to the meters' (-).
Now use the meter's(+) lead, having taken note of the voltage at the battery, to probe and measure the voltage a few feet away from the battery at all the leads that come off it. If there is no loading on any of the leads, they will be the same voltage, to the milivolt, as the battery, because their resistance is not high enough to cause a reduction in voltage with no load but the meter applied to them. But if one of those leads has a drain, even tiny, it'll measure a few millivolts less -a few feet away- due to its resistance.
The reason for the long ground lead is that you need a constant, unvarying reference point for your measurements. So a long ground wire hooked to the negative battery post is about as constant as you can get...
Once you've found that lead, you're on the path to your drain. You start down it and do the same thing on all of it's branch-offs. It's kind-of like following a tree from it's trunk to the tip of one branch. Eventually you can follow the drain to it's source by following the ever-decreasing voltage reading as you get closer to the drain. Once you think you've found it, you can disconnect it and take a final measurement at the wire you just disconnected; the voltage on that lead should go back up to the first noted voltage... wheee, you found the culprit!!!
You will need a 4-1/2 digit voltmeter instead of the usual 3-1/2, because only the 4-1/2 will read down to individual millivolts, and the drop might not be big enough to see with a 3-1/2.
This is a tried and true tested method by the way, by me... I used to track shorts down on printed circuits by using a very similar method. It is surprising how easy it is to track down drains and shorts once you get the hang of it. In terms of millivolts, the effect of a small load on even a thick wire is obvious.
The one caveat on this is that if there is a drain and you're powering this all by the battery, the battery voltage will be slowly counting down anyway as the battery discharges, making the initial reference voltage difficult to keep track of. It would work a lot better if you temporarily replaced the battery with a highly regulated 15 volt electronic power supply (mimics 14.7 volts better than a 12 volt one would), such as this one you could purchase from All electronics for 12 bucks.
15_VDC,_2.4_AMP_SWITCHING_SUPPLY
This supply is only 2.4 amps which means it's not big enough if your drain is over that amount. But if you have a drain that's over 2.5 amps, you should simply be able to see leads spark in the dark when you remove them, making all the above unnecessary. Or you could buy a bigger power supply, still cheap, from someone like MPJA
12 volt 12.5 amp supply
So there you have a reasonably inexpensive, actual tool instead of trying to outguess something you can't see... and it works a lot better than throwing expensive parts at the problem until it's fixed.... |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 12:57 pm: | |
I use one of two methods to find a problem like this.
Method one: With the battery in a shady or darker area, to make it easy to see a small arc, remove the ground cable from the battery. Then flash this cable against the battery ground post. If there is a load of even a few milliamps of current, there will be a small arc when you flash the cable to the battery post. The smaller the flash, the smaller the load. It is then a simple matter to start pulling fuses or disconnecting wires until the flash goes away.
Method two: Disconnect the battery ground cable. Connect a 12 volt test light or bulb between the battery post and the ground cable you removed. If there is an electrical load or short anywhere in the bus, the light bulb will light. The brighter the light the larger the load. Again, start removing fuses or wires until the light goes dark. Quick, easy and cheap.
Richard |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 15, 2006 - 5:43 am: | |
"Then wire hot to one switch contact and on the the alternator from the other contact"
This will only work onvce or twice ,
then the switch will be toast.
A bus alt needs a field current of 8A or so, far beyond what the normal oil pressure switch can handle.
Hence the switch & relay sugestion.
Of course if the relay ALSO locks out the starter circuit , youre back to std coach wiring.
FAST FRED |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 15, 2006 - 9:05 am: | |
With Richard's idea, substitute a cheap Radio Shack buzzer
(or tone module) in place of the light. When the noise stops,
you'll know you've located the draw. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 15, 2006 - 1:59 pm: | |
Maybe so FF, but my Eagle worked like that for the 15+ years I had it without any problem.
FYI, unlike many of the posters on this board, I typically do not offer suggestions or recommendations if I have not actually tried it.
John, Great idea. Why in all these years did I not think of that. LOL
Be aware that a very light load will not illuminate the bulb to full brilliance and may not energize the buzzer to maximum output.
Richard |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 15, 2006 - 7:28 pm: | |
Yeah... btdt.
The tone module I had, worked down to the minnie-winnie
load. Not LOUD, youse unnerstan... but more intelligible than me...
I traced my "draw" to the alternator. From what I've read,
they all draw some volts while sitting off.. This must be a fairly
common problem, if so many have to use the battery disconnect
to keep the batteries from failing. |
Stephen Fessenden (Sffess)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 17, 2006 - 1:26 am: | |
I bought a car that would run down the batteries overnight. There was a short in the alternator. Might want to get the alternator checked at a real shop or just replace it if it is not an expensive one.
To find out it was the alternator, I disconnected it overnight: battery was fine. Reconnectded the next night and battery was dead in one day. |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 06, 2006 - 12:54 am: | |
For those who are interested, if the field in an alternator is left on for an hour while the engine is stopped, a hand placed on the outside of the alternator will feel distinctly warmer than it would otherwise.
This will be the case if it can discharge the batteries in a single day. All the lost power turns into heat.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska 99901 |
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