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guy99 · 03-01-2006, 10:38 AM

Since this summer I have had four(4) alternators fail in my MH, the one that was in it when I bought the MH plus 3 rebuilts. One Autozone, two NAPA. They have all failed for different reasons so I don't think its the MH.

Any recommendations on brand and source for something which will last?

Pat370 · 03-01-2006, 11:21 AM

Sounds to me that you are not getting a large enough alternator for your application. Your GM type alternators have the voltage regulator built into the unit. If your need for constant heavy charge your regulator will never ingage to give the alternator a rest and a chance to cool down. High heat will kill a alternator in short time. I would suggest that you buy a lager Amp output alternator that is larger than you need. This way it won't have to work so hard.

Good luck
Pat370

davidh · 03-01-2006, 11:25 AM

I use to have troubles with reman alts to, also reman water pumps. When I was pulling wrenches on heavy trucks, we always tried to replace with factory new parts, seemed like the reman parts were always coming back to be replaced.

Pat370 · 03-01-2006, 11:32 AM

David, you are so correct. The only rebuilt parts I have had any luck with is oem rebuilt parts such as GM or Ford. Also with them if they fail your warrantee is longer and it covers the replacement labor cost.

Pat370

ralley · 03-01-2006, 11:40 AM

Strange--I am doing the same thing, and finding the stock rebuild delco-remy an absolute b**tch to get in. I'm out the door to buy a mirror to buy a mirror so I can see to align the front bracket and alt housing. If I had the time, I would look at a large capacity alt such as those used on ambulances and schoolbuses. The stock ones chevy 454 ones are, if memory serves, 50-70 Amps, which doesn't even come close to what you need, particularly if your charging time/driving time is short between uses.

Rob Alley

str8strm · 03-01-2006, 11:45 AM

There are a few other threads on alternators, we have a 135 amp that seems to work great--it does take a non stock belt though. AlanSD has used www.4alterstart.com

ALANSD · 03-01-2006, 12:57 PM

Quote:

Originally Posted by str8strm

There are a few other threads on alternators, we have a 135 amp that seems to work great--it does take a non stock belt though. AlanSD has used www.4alterstart.com

I have been very pleased for three years now with that item. I also got a heat protected aluminum starter from them.

guy99 · 03-01-2006, 02:32 PM

Alan,
What year is you motohome and which model alternator did you install?

I just spoke with these guys at 4alterstart and they said they have no application guide for motorhomes and so can tell me which alternator will fit.

guy99 · 03-01-2006, 04:38 PM

Well, I just bought a "large frame" 250 amp alternator from them.

Here's the whole tail. First my volt gauge has be screwy since I bought the MH. Sometimes it would read 10.5, sometimes it would read 12+. I figured I had a bad gauge which meant there was no good way to monitor what the alternator was doing. This summer while in North Dakota I had a problem with my batteries not being fully charged after a full day of driving. I replaced the alternator with one rate at 125 amps. All seems good for a while. After a few months and a few thousand miles, I noticed the volt gauge being even lower than usual, so I asked the shop to look at it. They reported that the alternator was bad and replaced it. I didn't think to ask about the output of the new alternator. That alternator began to have noisy bearings so they stuck in a new one which developed a short in less than a week and ran down my chassis battery. Now I remember to ask about the rating of the alternator which I find out is 78 amp. I say this won't do. This is when I posted here and began doing research, in the interim the shop calls a local alternator shop and he tells them that if one of may batteries is bad, or I run the hose batteries down real far (say I use 200 amp hours), it could cause the alternator to run at maximum output for a long time, overheating it and causing failures.

I'm tired of failing alternators and run down batteries so after speaking with the guys at www.4alterstart.com, I went with the 250 amp job. We'll see how that works, also I'll find out if my chassis battery is ok after being fully discharged a couple of times before I figured out the my alternator was shorted.

ralley · 03-01-2006, 05:19 PM

An update on my note above: I ended up taking back the alt which I got from my local parts guys--the case was too small to fit on the supposedly standard GM 454 bracket, so they called the remaufacurer and ordered a larger case--I ASSUME it will be about 105 AMPS. While clearly not enough Amps, I usually leave home with fully charged batteries and augment charging with a solar panel, for a 2 day trip, so we shall see how it goes.

Guy99: if your alt works out, please share the part number with the rest of us. I, for one, will duplicate your work and put my (presumably) 105 Amp alt in the spares box (with the spare coil) against future need. It seems to me that, given proper regulation, you cannot have too much charging capacity.
Will you need to increase the size of your wire from alt to battery isolator, if you have one? Or the size of the isolator?

Rob Alley

guy99 · 03-01-2006, 05:27 PM

You need to use 4 gauge wire from the alternator to the 'isolator' which in my case is actually a relay.

I too generally leave home with fully charged batteries, but a night or two of boondocking and my coach batteries are down quite a bit.

swebster · 03-01-2006, 05:39 PM

Anyone ever considered running two alternators? I've been kicking it around a little. I think I could mount a second alternator on the passenger side accessory bracket (replacing the my disconnected AIR pump) below the current alternator. We're adding more and more power loads as we rennovate the interior and I don't want to run the genny all the time to power up the coach "stuff" while enroute.

Has anyone done this?

guy99 · 03-01-2006, 05:43 PM

How would you wire them? In parallel? What would happen if one shorted out like my last one?

swebster · 03-01-2006, 05:56 PM

Not sure. I would want to isolate them from each other and allow (even if manual) the disconnection of a failed alternator from the circuit.

guy99 · 03-01-2006, 06:10 PM

There is some mention of dual alternator brackets at www.4alterstart.com. Maybe they have ideas about how this should be done. I've spoken to two fellow there and they were both quite helpful.

overlander63 · 03-01-2006, 06:12 PM

Why not wire your second alternator to charge only the two house batteries? That will allow the main alternator to charge the main battery, as well as run the secondary engine systems. Those secondary systems are a huge load on an alternator, and if you take them away from the second alternator, you would probably be equalising the load between the two somewhat.
Headlights are about 7 amps or so, the clearance lights another 3 or more amps, the electric fuel pump can draw up to 10 amps, and the A/C compressor on the engine, and the interior fans to blow cool air on you are another 20 amps. That is 50 amps, not counting operating the ECM (computer) and ignition system.

shadejo · 03-01-2006, 06:28 PM

I'm with Terry, if you are going to go to the trouble of a second alternator, I'd use one for the house batteries and one for the chassis battery. With this setup one could also do away with the isolator box that allows the one alternator to feed the two battery sets. Downside may be the belting arrangement on the engine. I don't think a single v belt could handle the two alternators, one of the ribbed belt setups as used on later 454's might do it but I can see where one may get into a lot of parts replacements to get this setup to work. And of course there will be some wiring required to feed the battery banks separately.

I think its definitely doable, but I'm not sure it would be worth all the work for me.....

Just my 2 cents (Canadian !)
John

Pat370 · 03-01-2006, 07:11 PM

Don,t do it. You could have a major burn out if one should put out more amps or voltage then it would backfeed into
the other and blow out the diodes.

Better to buy a larger alternator
and stay with just one,

Pat370

overlander63 · 03-01-2006, 08:02 PM

Quote:

Originally Posted by Pat370

Don,t do it. You could have a major burn out if one should put out more amps or voltage then it would backfeed into
the other and blow out the diodes.

Better to buy a larger alternator
and stay with just one,

Pat370

That's the advantage with my scheme. The two systems are completely seperate, with no chance of backfeeding since they are completely seperate. The disadvantage is the second alternator would be run by a very thin belt driven by the water pump.

GlenCoombe · 03-01-2006, 08:14 PM

Alternators are a DRAG...on the engine. Why not figure out your true maximum load, add say 25% or so and get the right alternator for the job?
Big alternators take quite a bit of horsepower to drive. This has an effect on how your motor runs, cools, and gives you economy.
Overkill on the alternator may not be in your best interst .... go for the proper size in MHO.