| Author | Message | ||
| phil shannon (198.81.26.108) Rating: N/A |
Hello all, My owners wiring manual says the 4104 has a positive ground battery system. When I bought the bus both batterys had the negative terminals grounded directly to the batt conmpartment side wall with a grounding stud (bolt). I cant imagine what difference it makes whether the positive terminals are grounded or the negative terminals are grounded. Wont the battery work the same either way? I ve had constant battery problems since I bought the bus. Batts wont hold charge long, difficult to charge, always dead even when disconnected thru dual batt selector to off(1,2 both, off). I am beginning to suspect that the RV place where I bought the Bus didnt realize it had a positive ground system and they installed two new batteries with a negative ground ignoring what it may have had before. From what I can tell, the bus side of the Motorhome is all still wired original. Should I attempt to reestablish the Positive ground configuration? Does it matter? What are some of the benefits and disadvantages of the positive ground system? What are some characteristics I should expect? Your advice please. Phil 4104-3832 | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
Phil - The 4104s were all postive ground systems when they left the factory. However, nowdays the majority of them, especially those in RV service, have been converted to the more common negative ground. I wouldn't get in and switch the grounding from what's there now UNTIL I spent a considerable amount of time sleuthing around the various chassis electrical components to find out if they're wired negatively grounded. An automotive stereo radio would be a good place to start - if it's an "off-the-shelf" brand-name unit(Pioneer, Sony, Alpine, etc.), it would be very, very unusual for it to be postive ground. Get the model number off it and check with the manufacturer, or a local auto stereo shop that handles that brand. If you hook most common auto stereos up positively grounded, they'll fry themselves the instant you turn them on! Suggest you pull the batteries out of the bus, make sure the water level is correct, and charge each one individually with a decent "floating" type charger for 12-36 hours. Then, using a battery hydrometer (available from NAPA and inexpensive), check each cell. If you get even one cell that doesn't read "in the green", the battery's toast, and needs to be replaced. Once you've determined that your batteries are good and fully charged, then you can start to track down where in the system you've got a drain that's discharging them. Cure the drain, and your batteries will thank you! HTH, RJ PD4106-2784 Fresno CA PS: PD4104-3832 - Transcontinental Bus System (Continental Central Lines)[i.e. Trailways], Dallas, TX. #3141 when new in April of 1958. | ||
| Jayjay (198.81.26.108) Rating: N/A |
Don't fry a good radio, (or even a bad one!) beg, borrow, steal, or heaven forbid, buy a digital voltmeter. They start at about $15.00 and when you put the leads on the battery terminals, the LCD screen will show a plus or minus sign (usually up in a corner) to indicate what the polarity is, with the red lead being the positive lead. To double check it, just reverse the leads and look for the minus sign to appear. This will not harm the meter in any way. Since it is obvious that you are uncertain about the system, remember this: with multi-battery systems the amperage capacity goes sky high in a hurry, and they have the potential to do serious damage to the coach body, or to your body. If you have a generator instead of an alternator, then it may need polarized to work properly. Hooking up a generator backward will fry the regulator (NAPA doesn't have them to fit a 4104), and if it is an alternator you will fry both the regulator, and the alternator. In either of these scenarios you stand a chance of melting insulation off the various wires involved and possible arcing and fire, so keep a dry chmeical extinguisher handy. Two 8D batteries have enough amperage/voltage capacity to weld 3/16 in. plate steel with a 5/32 mild steel rod, not to mention the explosive hydrogen gas produced. We all (me too!) tend to be careless with our battery systems, but all it takes is one little slip, and you could quickly be on a first name basis with your friendly local cosmetic surgeon! Electrical burns heal slowly and infect easily. Be careful! Cheers...JJ | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
JJ - I wasn't suggesting frying a good radio - I was just suggesting to Phil to find the model number and ask an auto stereo shop whether it's a positive or negative ground unit. I certainly agree about the digital voltmeter - well worth the investment! I've ruined two in my business w/in the last 18 months - they don't work too well after being dropped in a swimming pool. . . 8^( RJ | ||
| FAST FRED (209.26.115.217) Rating: N/A |
If your a FMCA member (or have a buddy) they have a great article on converting to negative ground. Call & ask for a copy , free service for members. Lots easier to switch over & be able to use all the RV stuff as is. FAST FRED | ||
| Pete (152.163.188.227)
Rating: N/A |
Phil, Due to the previous owner doing a partial conversion..I have the same thing..oridiginal is positive ground..all new is neg ground. I have done alot of work checking things out..where what goes where and have even managed to short everything out in the entire bus. Email me direct with your prob..maybe my screw ups can help you before you fry something by accident Pete Maybedream@aol.com | ||
| phil shannon (198.81.26.108) Rating: N/A |
Hey everyone, let me back up a bit. When I said "I cant imagine what difference it makes whether the positive terminals are grounded or the negative terminals are grounded and, Wont the battery work the same either way?" I wasn't saying Im clueless on electrical issues, I realize that for motors and radios and lots of othe things, that polarity does make a difference. I have a digital volt meter as well, however the concept of a positive ground is new to me. So let me ask my questions again: Theoreticaly, If I were to re-establish a positive ground system one circuit at a time,correctly, with no problems whatsoever, then what would be the benefits of doing this over keeping a negative ground system? What are the disadvantages? In the old days, why did they use positive grounds? Why do most people convert over to a negative ground? Is it just to make it capatible with modern components which use negative grounds? Best regards, Phil Shanon | ||
| Dale Fleener (66.81.128.87)
Rating: N/A |
Phil, Your thoughts about why people switch over to neg ground are probably right. IMHO FF has a good suggestion, one you should check out. Dale MC8 (who has a 24 volt system) | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Phil, the bottom line is that it is simply a flip of the coin as to whether a designer creates a bus with positive or negative ground. As long as all the components (motors, electronics, gauges etc) are connected properly, it doesn't make any difference at all which way the designer chooses to do it. Of course standardization is an issue, and sometimes designers break tradition specifically to make it hard for people to buy parts from other manucfacturers, but otherwise there's no difference at all. Funny how it started... way back when when electricity was discovered, it was known that there should be positive and negative. But no one actually knew which terminal was actually "supplying" the electrons and which terminal they were returning to. So they took a guess, and called positive the one the electrons come from and negative the one they return to. They screwed up. It turns out that electrons actually flow the other way, from negative to positive!! Oops.... but by the time we found out, it was waaay too late, and batteries have been polarized that way ever since!! Well, so much for it really mattering....  Cheers Gary | ||
| Jayjay (198.81.26.108) Rating: N/A |
Hey RJ, put that ball bat down! I went back and re-read your post and realized a misunderstanding on my part. BlanksdorfCorp, located in Wherzitat, Cal. has a new line of interactive digital meters that either swim or fly, depending upon the mode set in the CPU prior to the P.O.S.T. Kinda' spendy, but I sure like mine. ...JJ | ||
| Peter Broadribb (Madbrit) (65.37.88.171)
Rating: N/A |
The reason that vehicles are now negative ground is because it was "discovered" that there was less corrosion in a vehicle that had a negative ground system over one with a positive ground system. If I remember correctly, this was an electrolysis problem. Peter. | ||
| Jim Stacy (12.87.109.6)
Rating: N/A |
In any case, Phil it's a whole lot easier to hook up new apliances if the rig is negative ground. Many pieces of audio and communication gear have the case and antenna mount internally connected to negative. I believe the 1960 4104 was the last positive ground bus. The last Detroit built car was in 1955 as I remember. The changeover is not a big deal. Get the FMCA article as Fast Fred sugests, or call Coach Info Network. They have a similar article. Jim Stacy (1953 4104, negative ground) | ||
| REX (140.183.65.19)
Rating: N/A |
Phil. 15 years ago, without any knowledge about busnut's or BB's I took the generator off my 6-71 (PD4104)and added a 100 amp alt (with built-in regulator). For this installation I got a gear driven double belt pully from DD dealer and welded up a bracket to mount the alt. I then reversed the battery cables. I do not know what is right or wrong, however this has served me without any problems. Had I known that there were articles available I would have researched at the time. Good luck to you, and as a member of FMCA I think I will get the article and see what they have to say! | ||
| Jim-Bob (12.46.52.74) Rating: N/A |
Rex, I'll bet your Heat/Oil pressure/Air pressure/Rear door alarm buzzer in the electrical panel under the driver's window doesn't work! Other than that & the generator polarity (which you fixed by removing it) I think that's it. |