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Car damaging the alternator?

Posted By: Spetz

Car damaging the alternator? - 06/11/18 04:46 AM

Hi everyone,

About 6,000 miles ago (many years though) the alternator on my 6A12 MIVEC swapped Mitsubishi Mirage started failing. Unsure on history of the original alternator.

It was replaced with an aftermarket alternator which lasted 6,000 miles.
It started throwing an error code for FR terminal however was still usable and charging.
It also drained the battery but the car is rarely used so I would just disconnect the battery when not in use.

I replaced it with a second hand genuine alternator (23 years old to be fair) and the same error code was appearing (FR terminal).
At this stage I swapped in a spare ECU I had for the car, same issue.

I then had the genuine alternator rebuilt.
Upon installation it worked great. No errors codes, charging fine.
But it only lasted about a half hour and it stopped charging completely (not just an error code like previous alternators).


Is it possible something is damaging the alternator?
How would I test something like this?
Posted By: clinebarger

Re: Car damaging the alternator? - 06/11/18 05:56 AM

How is it wired?...Do you have a diagram? Not sure a US market car is wired the same....
Posted By: Audios

Re: Car damaging the alternator? - 06/11/18 05:29 PM

Check the ground cables, make sure there is no corrosion inside the cables, or feel them if they get warm/hot, theres a ground problem.
Posted By: Audios

Re: Car damaging the alternator? - 06/11/18 05:29 PM

Also hows the battery?
Posted By: Spetz

Re: Car damaging the alternator? - 06/12/18 12:08 AM

The ground wire that goes from the negative battery terminal to the chassis?
I will check however from looking at it before it seemed fine.

The battery is new. It is a small battery though (the car is used only on the race track).
However the old alternator had a parasitic drain for a while which I just disconnected the battery when not in use.
Posted By: talest

Re: Car damaging the alternator? - 06/12/18 12:12 AM

Originally Posted By: clinebarger
How is it wired?...Do you have a diagram? Not sure a US market car is wired the same....


I don't think they are, either.

It may or may not be, but is it like this ?

Posted By: Spetz

Re: Car damaging the alternator? - 06/12/18 01:16 AM

I am unsure how it is wired but there is a signal to and from the ECU.
So I believe the ECU controls it in a way.

However as mentioned I swapped ECUs thinking that might be the issue and it behaved exactly the same.
Posted By: clinebarger

Re: Car damaging the alternator? - 06/20/18 03:46 AM

Originally Posted By: Spetz
I am unsure how it is wired but there is a signal to and from the ECU.
So I believe the ECU controls it in a way.

However as mentioned I swapped ECUs thinking that might be the issue and it behaved exactly the same.


I was looking over some Mitsubishi diagrams, I used a 2003 Diamante for the example......

It appears the the ECM just monitors the "Lamp/Turn-on" for incorrect voltages (High/Low) & sends a data signal to the gauge cluster if a fault is present. The Cluster uses a transistor to control the Charging Lamp

The Generator Relay Coil is what passes a resisted ignition hot turn-on signal to the regulator.



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