1995 Mitsubishi Diamante electrical issues

BSTEADMAN

MEMBER
1995 MITSUBISHI DIAMANTE
3.0L
V6
FWD
AUTOMATIC
139,000 MILES

Lately while driving my car it would just all of sudden die. And would not restart without jump starting it. Took it to AutoZone and they tested the battery, alternator, etc. Came to the conclusion it was the voltage regulator that was bad. So I've replaced the alternator twice with used ones and it did the same thing. So I bought a new alternator and it still does the same thing. It's ok as long as I don't run my headlights or radio or heater while I'm driving, but you add any kind of a load and it is sure to die. What else can I check?

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

First measure the battery voltage with the engine running. It must be between 13.75 and 14.75 volts. If that is okay, have the generator professionally load-tested to see how much current it can develop. If it has one bad diode of the six, you will only be able to get exactly one third of its rated current. 30 amps from the common 90 amp generator is not enough to run the entire electrical system under all conditions. With a bad diode, "ripple" voltage will also be very high. The testers at most auto parts stores only check to see if there is some current output, not how much.

If you find the battery voltage is lower than 13.75 volts, measure the voltage on the large output terminal on the back of the generator with the engine off. You must find full battery voltage there all the time. If you find 0 volts, look for a blown very large fuse or fuse link wire.