2003 Mitsubishi Montero Sport alternator

LECTRON99

MEMBER
2003 MITSUBISHI MONTERO
6 CYL
2WD
AUTOMATIC

In the last 2 years I have replaced the alternator 5 times. Each time I returned the alternator it did check bad.I was told by a the store manger, who is a mechanic, that the computer was causing the alternator to burn up. I got a computer but as I said now the car won't start. Dealer says they can flash the computer or my keys. With the original computer the car starts and runs fine. Before I spend much more on this problem, does it make sense that the computer is causing this problem? I would appreciate another opinion. I have looked at the wiring diagram for the vehicle and cannot see where the computer ties in to the charging circuit.

6 Replies

CARADIODOC

MECHANIC
33,742 POSTS

GM has a huge problem with repeat failures of their generators caused by an old battery. You might be running into the same situation. Due to the design of their voltage regulator, it switches on and off hundreds of times per second. The ratio of on-time to off-time varies to control the charging rate. Since it turns current flow off instantly, just like in an ignition coil, the coil of wire in the generator creates a big voltage spike. Those spikes can destroy the internal diodes and voltage regulator.

Part of the battery's job is to absorb and dampen those spikes. As they age, they loose their ability to do that even though they still crank the engine just fine. What many professionals are finding out with the GM products is to reduce those repeat failures, they replace the battery at the same time as the generator.

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Tuesday, August 9th, 2011 AT 1:13 AM

LECTRON99

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3 POSTS

Thanks for the reply, but the battery is only about 6 months old. We ended up taking the car to a dealership and they reprogrammed the key so it would work with the new computer for about $50 per key and it cranked right up, hopefully it will solve the problem of replacing the alternators, if you don't hear from me, it has been fixed, thanks again.

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Wednesday, August 10th, 2011 AT 11:11 PM

FIXITMR

MECHANIC
9,990 POSTS

Hows it working so far?

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Monday, September 12th, 2011 AT 12:58 AM

LECTRON99

MEMBER
3 POSTS

So far, so good -we haven't had any problems, hopefully it was the computer, I'll try to remember to update this if anything changes, thanks so much for this site and to all the people who share your knowledge with people like me who need help.

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Friday, September 16th, 2011 AT 1:58 AM

NOVICE82

MEMBER
1 POST

I have had the exact same problem with my 2003 Montero Sport and it has been frustrating. I am on my 4th alternator in a little over a year. Where did you get your computer from and did you install it yourself?