A buddy's car is broke down in the parking lot. We verified battery voltage is
10v with motor running (jump start and definitely not charging). The book he has says could be the PCM maybe (powertrain control module) or obviously could be the alternator. Apparently the PCM houses the voltage regulator. The book also shows a relay in the PCM circuit. We think we found the relay and swapped it with the wiper relay but no help.
How can you test on the car which is bad? (plan to pull alternator and have it tested)
The PCM is located on the passenger's side of the engine compartment, behind the air-cleaner box.
The voltage regulator is indeed located inside the PCM... BUT:
1) the voltage regulator on that type car almost NEVER fails
2) if it DOES fail you can wire in a 1971-1989 Chrysler external voltage regulator to do the job instead. Dan Stern has posted the technique for doing that before and probably has it on-file if you need it again.
What I've had happen on my 93 is for the brushes in the Nippondenso alternator to wear out. Another common Nippondenso failure is for the rectifier ground connection on the back of the alternator to fail. All the ground current is carried through a sheet-metal back cover to a single screw, and it can become the "hot spot" (literally) in the charging circuit.
The "poor man's" on-car test of the alternator is to briefly (BRIEFLY!!! as in 1 second or so) full-field the alternator by supplying power and ground to the two smaller terminals on the back of the alternator with the engine running. Battery voltage should jump up and you should be able to hear the alternator "load down" the engine if its working. You could also use an ohmmeter across those two terminals with the engine shut down and the wiring harness disconnected from the alternator. Resistance should be nearly zero- when the brushes fail it will usually read much higher or even open-circuit. It is possible for the alternator to fail in various other ways too, so just taking it to the parts store and checking it is probably the quickest way to get a conclusive answer. If it is bad, LEAVE the parts store and have it rebuilt at a local starter/alternator shop if you have one. Parts-store alternators are usually junk.
Steve, Thanks for the detailed response. A little more info on my part is he did just recently have the power steering pump fail and spray oil all over the alternator and had to remove it to get pump out. We were wondering about the brushes and how much they would like to have an oil bath and your comment about the ground wire is also worth checking.
No problem, since I own the same model car I can speak first-hand :-)
Check out the wiring, too. IF work was done in that area, flexing the wiring harness could have broken a wire. Don't know about this car, but some of the wiring is starting to get brittle on my '93 after 11 Texas summers.
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