Hmmwv alternator overcharge and belt squeal.

[Kswiney]

I am having an unusual problem. I had an alternator all of a sudden start overcharging and would make the belt squeal. Took it to a shop and they are doing the repairs. In the mean time I purchased a used alternator installed it and everything was fine for 1 week. Now I'm getting the same thing. Again as before it's not constant but its becoming more frequent. And yesterday a new symptom.. The fan now runs constantly. I have been looking thorough the TM's with little luck. I went through several test to no avail. What are the odds both alternators went belly up so. And now the fan, I'm at a loss. Any help is appreciated.


Thanks,
Kyle

 

[papakb]

In the common military 60 amp alternator overcharging is a symptom of the 50 watt resistor in the regulator blowing out. Jumpy voltage is a symptom of the brushes wearing out and low voltage output is usually indicative of a regulator failure. If that's all that's happened they can be replaced pretty easily. If something else failed in the regulator it means changing out the regulator assembly on the back of the alternator. Also a pretty simple job, 6 screws and pop the unit out. It can be done with the alternator in the vehicle. If it's one of the larger alternators you've got a bit more work ahead of you.

The fan issue is commonly due to a failed time delay module. Belt tension is also a problem especially if the truck has mismatched belts on it. The belts on the alternator and the belts on the power steering pump are both matched sets and should always be changed together. If you buy a pair of belts from your local auto parts store look at the date codes stamped on them and try to get 2 that were made the same day. At least you'll have a chance that they're close together in size. The other option is to buy a matched set from one of the surplus dealers out there.