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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8594
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have 2005 Mitsubishi eclipse that died when driving. The

Customer Question

I have 2005 Mitsubishi eclipse that died when driving. The battery light came on before this happened. jumped car and checked charging was not so i removed alternator 7.5 fuse thinking it was blown. when i removed fuse chrging jumped way up to almost 18 volts so i assume alternator good. But why would charging go up if fuse removed I thought fuse supplied power to alternator
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.


This vehicle uses dual regulation, an internal regulator in the alternator that is controlled by the PCM.
If you jumpstart the vehicle (all fuses in) what is the operating voltage on the battery, or does it die immediately?

Customer: replied 1 year ago.
This problem has happened 3 times in the past week. When I jump started the last time it was showing just over 9 volts. What i did was after I started removed alternator fuse which it then showed high charging then i replaced the fuse and it showed normal charging about 13.75 volts. I checked fuse connections used different fuse to make sure it was not a connection issue.Works fine for a day or so after putting fuse back in until the Battery light comes on and lights will dim. I had battery checked at autozone and showed OK
Expert:  Doug replied 1 year ago.

Thanks. Do you think you can get it running/idling long enough to take some readings off the alternator PCM connector?

There isn't anything in the history to be aware of, like the alternator having been replaced with aftermarket in the past etc

Customer: replied 1 year ago.
the alternator has not been replaced since I owned the car for 3 years.
Expert:  Doug replied 1 year ago.

I'm sorry for the delay.

Having the alternator over charge with the fuse out is a bit disconcerting and would usually indicate the regulator inside the alternator is bad. The regulation system needs to be tested though to identify the issue..... of course fuses need to be installed and verified good as well as battery cables verified intact and not corroded etc.

With the engine idling and all loads off, you will need to put a DC meter between ground and one of the outer pins of the four pin connector on the alternator (connector plugged in) and measure the voltage. Then turn on the blower motor on high and take the voltage reading. Then the defroster, then the high beams.

Turn all loads off and move the meter lead to the other outer pin on the four pin connector and repeat the above steps.

If you see one wire start around 0V and slowly increase in voltage as each load is added, then the other starting at higher voltage (between 5-12v) and slowly decreasing as you add loads, then the PCM control is fine.... you need a new alternator.

If you have one or both wires not behaving as described and showing fixed 0V or fixed 12V for example, then the PCM is suspect.... you would want to verify you don't have any wiring damage and if not then replace the PCM (requires dealer to key program).

The majority of the time it is the alternator. Be aware that you can not use aftermarket alternators on these cars... they do not work properly in these vehicles and in some cases (NAPA, Duralast) they have been known to damage the PCM making a bad condition much worse.