dead alt?

anyway, i get 12.5V at the batt, engine off. engine on, i get 11.8V at the batt, and 11.8V at the alternator output post. turn the motor off, i still get 12V+ at the batt. with the engine running i loaded the alt (multimeter still running from the output post and neg batt terminal) by turning on my a/c and lights and i lost about .8V. is it worth trying to pull a code to check for the voltage regulator being bad in the computer? (93XJ, OBDI)

before I drop $150 on a 165A alt, i just wanna make sure im not overlooking something.

A quick check for a dead regulator (on the externally-regulated NDs) is to take your meter and check for voltage going into one or the other of the regulator contact studs on the back of the case - you should see 3-4VDC into one or the other of them (the other one should have direct continuity to ground.)

Fortunately, the regulator circuit in the PCM rarely goes bad on you - chances are, you've blown your alternator. Either the field coils are shorted out, they've lost contact, the brushes are shot, or the diodes are blown out. How to tell? You'll have to tear the thing to bits to find out.

Parts for the ND are relatively common - but if you don't know your way around the inside of an alternator, you're just as well replacing the whole thing. You'll probably come out about even after having "shotgunned" the repair, and you'll definitely be ahead on time...

thanks, i printed out some huge quick troubleshooting you wrote on some thread i found on here :thumbup:

i'll check out what you said, im probably just gonna pick up a 165A from alterstart, http://superpageshosting.com/4alter...mmon/sitesearch.nhtml?query=jeep&catuid=10013

its about the same price as a good lifetime warranty replacement, but, better.

93XJLI said:

thanks, i printed out some huge quick troubleshooting you wrote on some thread i found on here :thumbup:

i'll check out what you said, im probably just gonna pick up a 165A from alterstart, http://superpageshosting.com/4alter...mmon/sitesearch.nhtml?query=jeep&catuid=10013

its about the same price as a good lifetime warranty replacement, but, better.

Click to expand...

If you're getting it from a "chain" store, "good" and "lifetime warranty" tend to be mutually exclusive. I worked at a "chain" store (Kragen's) once upon a time, and I can attest to the "quality" of their parts (or lack thereof.)

That "lifetime warranty" is there because you're likely to need it. Typical return rate on starters and alternators ran something like 40% in any given monty. They come over by the forty-foot Conex box from China, and testing isn't very thorough.

Best bet? Find a local shop that does rewinds, if you're on a budget. If you've got the dosh, hit up one of the "high-power" rewinders.

NAPA and CarQuest do a decent job of their remans, but avoid Checker/Schuck's/Kragens/AutoZone/Pep Boys and the like - as far as I know, they're all in the same boat with their parts. That "China price" is going to kill us...