My 2000 mitsubishi montero sport XLS has been having troubles for about 2 months now. The brake and battery lights came on randomly since ive owned the car( June 2005), only when i would rev my engine to hard to brake to fast. The lights would then go away after a would rev it again or brake again usually. But in Jan 2007, the brake and battery light came on and stayed on for 2 days until my car died. Took my car to Firestone to have them put a new alternator in because mine had gone out. Then a day later my car kept stalling so i took it to a place near my house. they charged me 80 dollars to tell me that Firestone had not reconnected the alternator back properly. so after they fixed that my car worked for about 2 weeks and then it started driving funny and stalling out when i would stop at lights. took it back to firestone and they said it may have been a bad alternator and they replaced it under their warranty. My car ran fine for about 2 weeks again and then the brake and battery light started to come on again and my lights werent bright anymore and the radio wouldnt come on. Went back to firestone and they would not replace the alternator again until i got my car checked out by an electrician because firestone felt that it coudnt have been another bad alternator, that it had to be an electrical short causing the alernator to short out. SO i took it to an electrician and he told me that my original alternator had caused a short in a wire that ran from the ignition to the alternator and that everytime a new alternator was put on, the short in that wire was frying the alternator. So he charged me 225 to find and fix the short. Firestone put a new alternator in under warranty and my car drove for about 2 weeks. Now my car is back at the electrician and he has tried to give me two reasons why it still isnt fixed:
1) my battery(even though it checks out perfectly fine at both places it was checked at) has a loose connection in it and might be causing the alternator to go bad everytime.
2)but then they sent my alternator to a "specialist" and apparently he thinks the problem is that there is an oil leak in my motor and oil is getting into my alternator causing the problem. Yet four alternators have been pulled off my car and only this last one has anyone said anything about oil being it it. I would think that the people at firestone would have noticed when they pulled off the others that there was oil in them. plus i have no oil dripping from my car, so i dont see how this could be the problem.

If anyone has had the similar problem or has any idea what might be causing this problem please let me know because i am about to have to buy another new alternator because firestone wont warranty it anymore and probably have them fix something they say is the problem again only for it to break in 2 weeks anyways. Ive spent close to 1000 already and have got no solutions. Please help me.

 

I'm having the exact same problem! My truck has been in the shop for 4 days. However, the mechanic tested the alternator and it was working properly. I experienced the same pattern with the brake lights coming on and the radio going out and then the truck just dying. Did they ever figure out the problem?

 

I am having the same issue....have a Montero Sport 01.....looks like I am going to have to replace alternator #4. This driving me nuts......seems to happen every 3 weeks.
Getting after market alternator from Advace Auto parts........

 

You guys might want to check the grounds in the engine bayand load test the wiring to the alternator. Deff sounds like a wiring issue.