2003 Mitsubishi Montero Sport alternator

Tiny
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.
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Tuesday, August 9th, 2011 AT 12:27 AM

6 Replies

Tiny
CARADIODOC
  • EXPERT
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
Tiny
LECTRON99
  • MEMBER
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
Tiny
FIXITMR
  • MEMBER
Hows it working so far?
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Monday, September 12th, 2011 AT 12:58 AM
Tiny
LECTRON99
  • MEMBER
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
Tiny
NOVICE82
  • MEMBER
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?
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Thursday, September 22nd, 2011 AT 7:49 PM
Tiny
JONATHON7500
  • MEMBER
Any updates? I have the same problem with my 2003 mitsubishi montero sport. I just dont know what to do anymore. I bought it with 10 miles on it and now I always have to replace either the alternator, starter, or battery. I will say I bought I higher amp alternator and it has worked for a year and 3 months but its out again. I literally just replaced the starter last friday. I checked to see if the alternator was good and it was working perfectly. I got a new battery but I know that will only last a few days.
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Friday, June 28th, 2013 AT 2:33 PM

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