The original converter on my bus changed it from 24 volt start to 12 volt but didn't relocate the batteries. We've been applying bandaids to that ever since we bought the bus. I've pretty well got it licked but I'm pretty hard on starters and I think I've got another failure coming on. This one has lasted 18 months so that is an improvement over the 3 that I put on in the first year. I don't want to even think about switching the whole bus back to 24 volt but John Deere used a 24 volt starter on a 12 volt system on some of their farm tractors in the 60's. Has anyone ever done this on a bus? The JD system had a solenoid that put the batteries in series for starting and switched them back to parallel for running.
There were a lot of trucks and some still do use a series parellel switch to start on 24 volt thats all then goes back to twelve volt for all other systems if you buy a series parellel swotch you should get wiring diagram or any good motor book on trucks should give you what you need. reccoment 4 series 31 12V batts
Larry H
I have a '72 flex with 8V71 & auto. when the starter went out 6 years ago I was in Tall. Fl. when I went to
a starter rebuild shop the man told me that someone had put a 24V stater in a system that had always been
12V. The alt. & wirering & starter & lights on that bus was biult 12V. The feild coils on the starter is what makes
differance he told me. I haven't had a problem with the right starter in 6 years. And now I plan to put that system
in my '77 MC8 because all that motorhome suff seems to be cheaper in 12V. So maby all you need is the right
starter. just a thought.
Ray with the littlehouse [south of seattle]
Ray, (with the littlehouse) you should consider leaving the MCI 24 volt system as it is. Take a opportunnity to hear an Detroit engine start with 12v and compare same type with 24 volts. The 24 volt starter just "Jumps" on it while the 12 is much slower. The 12 volt accessories are easily handled with a 24 volt house battery bank, mine (I also have 77 MC8) I use 8 six golf cart batteries with a Trace SW4024 inverter. Since the house bank and coach bank are both 24 volt, the bus alternator charges both systems, This system is capable of running 2 roof airs while underway...without the Onan.
All 12 volt loads, including the bus headlights are handled with a Vanner 24/12 equalizer.
this setup (+/-) is common on a lot of MCI conversions...because it works.....but its certainly not the only way
Two ways to go come to mind. First is to use the Delco MT42 24v starter that is a hugely heavy starter with a series/parallel switch. So you can start with 24v but run the bus on 12v. On trucks, this system is mostly not used anymore since superior 12v starters are available.
The new Delco MT39 is a 12v starter that is gear driven, have the size and weight and supposed to last twice as long as the MT42. It is sort of bazzar when you start one of the new trucks with the MT39 and it sounds like a Toyota starter. But they work very well especially in low battery situation. Personally, I would use the new MT39. Good Luck, TomC
I drove a '56 Autocar(among others...showing my age) with a parallel switch and it was a pain. I know technology has progressed but IMHO if you can stay away from that type of system you will be better off. The old KISS principle. Conversely, I drove a numbers of later model ('60s & '70s) trucks with Detriots & Cummings that started on 12V & had very little problems as long as I kept up the maintainance. Good Luck!
Would it not be a lot easier, and in my opinion better and less expensive, to just increase the size of the battery cables. From your statement I have to assume that is the problem.
my Eagle was 12 volt starting and I never replaced a starter in the 15 years i owned her, so
I think you need to fix the basic problem. Richard
Quote from: bobofthenorth on July 27, 2006, 09:28:21 AM
The original converter on my bus changed it from 24 volt start to 12 volt but didn't relocate the batteries. We've been applying bandaids to that ever since we bought the bus. I've pretty well got it licked but I'm pretty hard on starters and I think I've got another failure coming on. This one has lasted 18 months so that is an improvement over the 3 that I put on in the first year. I don't want to even think about switching the whole bus back to 24 volt but John Deere used a 24 volt starter on a 12 volt system on some of their farm tractors in the 60's. Has anyone ever done this on a bus? The JD system had a solenoid that put the batteries in series for starting and switched them back to parallel for running.
Another point along the lines of battery cables. My transit bus has the batteries on the left side almost in the middle of the bus (front to back). Each battery cable is a 000 cable that goes uncut directly to the starter-so two big cables on the starter solenoid. The ground is also two big cables from the batteries directly to the chassis, then two big cables from the chassis to the starter. Plenty of starting power, the lights dim very little when starting inticating that there is little resistance to the starter. If your starter was 24volt originally, then changed to a 12v, the starting amps are double and if the cables are original, won't be big enough. Highly recommend using 000 cable times 2. Good Luck, TomC
We've already doubled the cable - 2 runs of 4-0 on the hot & ground. I agree with the KISS comments - I don't like the basic concept of 24/12 systems but I am at my wits end over this starter. Someday it is going to let me down on the road. I'm going to look into the heavier starter - I'm close to a solution now, just a little better starter would likely solve the problem permanently.
Quote from: TomC on July 28, 2006, 07:59:12 AM
Another point along the lines of battery cables. My transit bus has the batteries on the left side almost in the middle of the bus (front to back). Each battery cable is a 000 cable that goes uncut directly to the starter-so two big cables on the starter solenoid. The ground is also two big cables
Is 000 cable the same as 3/0?
My inverter recommends 4/0 for up to 15 feet and 350 MCM beyond that. I may be slightly over 15 feet. Will I be okay with 4/0? Can I run two 4/0 cables in parallel since I can get 4/0 for 25% of the cost of 350 MCM?
Brian Elfert
Yes, 000 is the same as 3/0. So 0000 is the same as 4/0.
3/0 is 168 MCM and 4/0 is 212 MCM
So 2 runs of 3/0 would be 336 MCM and 2 runs of 4/0 would be 424 MCM.
(MCM is thousand circular mils)
Len
Bob....be different,go with an airstarter,and let the batteries power something else..........*smiling*....Good luck with your situation..........Frank
Quote from: Bosshosssport96 on July 28, 2006, 05:35:45 PM
Bob....be different,go with an airstarter,and let the batteries power something else..........*smiling*....Good luck with your situation..........Frank
I like it - - - - - the debate goes on. . . . .
I found a place nearby that has the 39MT Delco starter. I just need to pull the old one out and take it with me to match up to the new one. Of course I won't know for a year or so whether this has helped (unless I know in a month or so that it hasn't).
Stay tuned.
Update:
1 false (non)start later. Apparently there are two 39MT starters that cross to "match" the starter that came off my 8-92. Guess which one I got first. NOT the one that worked. >:( As of last night I can again start the monster. Only time will tell if the problem is solved or just postponed.
Stay tuned.
Bob of the North, Good luck ! Have you considered moving the batteries close to the starter? Just my 2 cents worth ! And that my friend won't buy a darn thing these days ! BK ;D
If enough people put on their registrations that they are interested in having a great (the BEST in my opinion) Bus A/C man look at and discuss their A/C's with them I'll invite my A/C specialist to the "TN Fall Bus Bash"
But ya gotta register and put it on the registration form, so I know there is enough interest in it to ask him to take time out of his schedule to come over for a day! BK ;D
Quote from: Busted Knuckle on August 16, 2006, 08:23:46 PM
Bob of the North, Good luck ! Have you considered moving the batteries close to the starter? Just my 2 cents worth ! And that my friend won't buy a darn thing these days ! BK ;D
I've considered it at great length, sitting in a lawn chair with many beers to aid in my consideration. But I don't see how I can. If/when I change gennies it might be an option but the current location of the genset precludes moving the batteries. The last time I tackled this I went from 1 or 2 months per starter to 18 months per starter. If I have made a similar degree of improvement then it won't be a problem. Even if I can stretch it out to 3 or 4 years per starter then I could live with that.
mmmmmmmm......beeeeeeeeeeeerr........mmmmmmmmmmmm