What would cause an engine battery to short out, and ruin the alternator?
After a nice uneventful 1000 mile trip with no electrical problems, took the Breakaway to the shop to have the idle adjusted. Also had the shop repair some rust damage to the engine battery compartment. Got it back from the shop, and within 300 miles, the alternator failed which was traced back to a shorted out engine battery. I am thinking the shop did something when they put the engine batteries back in that caused one of them to short out. Thoughts please.

Have you determined for sure the engine battery is shorted; while rare, one will short out occasionally? If there is a weak grid, moving the battery might dislodge it. The shop would have no way of knowing. The battery could have been fine when reinstalled and the vibrations from the trip could have caused the short. I don't think anything the shop did is the cause.

The alternator should have 3 things protecting it:

1. Fusible link

2. Internal self-limiting. Most alternators reduce output if they get too hot.

3. Battery isolator. It should pass only the amount of current for which it's rated.

I'd suspect the isolator if the battery checks out good.

My alternator failed right after I bought this Breakaway. It happened after I ran the house batteries down rather far. It was a 90 amp unit and not up to what I was going to put the +12VDC systems thru. The alternator is mounted rather close to the turbo and all the air is drawn over the exhaust system by the alternator and thru the radiator. I think it died of natural causes.

I replaced it with a single wire 160 amp unit. I don't have battery isolators so it was not problem. To get a real 160 amp unit (100 amps at idle) requires a change of the alternator bracket, tensioner, and belt.

I recently replaced that alternator with a 200 amp 5 wire unit and now have a 3 stage external charging regulator controlling the alternator. Later I will put the 160 amp unit back in and use it to charge the chassis batteries and separate the house and chassis systems.

project 1001