I bought an alternator a while back, and it worked fine, for a while...

Volts drop to 12 at 3300rpm cruise. Run the fan and the lights and the wipers and watch the volts creep downward. Kill all the loads but the engine systems, and it creeps back up to 12.3 and NO higher. Finesse my hand down to the back of the alt and play with the plug. Works fine, for a while...

Volt drop again, same as before. Autozombie clerk lays the alt tester on it, and when he does the battery test, the engine dies from no 'lectrons. Bad battery, he says. See, it's always the battery is bad first at AutoZombie. New warranty battery. Charges to 12.3v at speed. Play with the plug. Nada. 12.3v.

On the way to the real auto parts store. Volts go to 16. Turn on all the loads. Volts go slowly down to 13.5 (normal city). Volts stay at 13.5, for a while...

Get in truck today. 12.0v at speed. Turn off loads. 12.1v. Drive 2 more miles. Whambo, 16v again, for a while.

Now it's running 12.5 or so under heavy loads, and 13.5 under light ones...

Autozombie clerk told me at least one of the diodes is bad. I don't think this computes, but 'lectrons and me aren't the best of friends...

Any of you 'lectron geniuses out there? My best guess is either an intermittent fault in the alt plug circuits, or a failing regulator.

Didn't somebody post about DO NOT do the HLA rpm fix on a Gen2 ??????. Something about voltage spikes straight thru the heart of the reg??

Tighten the alternator belt.

Connections or regulator in my opinion....

Ed

I'd suspect the voltage regulator, but first try the following:

1) Inspect the battery cables and body ground cables closely
2) Clean and reinstall the battery connections
3) Remove the ground strap connection on the passenger side fender and clean the connection area
4) Clean the body ground connection on the driver side fender
5) Remove and clean the block ground connection on both sides of the engine
6) Spray contact cleaner on the harness plug and alternator connectors

Ckeck the voltage drop between the battery (+) and alternator connector (B-02).

If it still acts up, I'd try disconnecting the light control relay (connection 3-R) and see what happens.

If it still insists on acting up, I'd replace the regulator (or alternator).

Frank

Where is the regulator on these? Is ist part of the alternator like everything I've worked on or is it separate?

If it does not turn out to be external wiring having been baked by heat, I would then question the brushes.
My experience the internal regulator either works or doesn't.
I have yet to see a remanufactured alternator with new brushes in it.
If the brushes are worn, they impose quite a load on the regulator.

Clay - the regulator is internal.

Charlie is correct about rebuilders not usually replacing brushes (unless worn out) - they also don't usually replace the regulators or diode/rectifiers..... which seems to be the larger problem with remanufactured alternators of the MMC variety.

Frank

Do any of ya'll have a source for these brushes, diodes and regulators? I've rebuilt a few alternators before and I have one from my Monty that pooped on me a few months back. I bought a salvage unit, because I don't like the build quality on most units (and they're SO damned expensive) I would like to overhaul this one to a little more amperage. Is that possible?

If you rebuild yours, take lots of photos!! I kept one of my old ones, just to try to rebuild it someday

Will do <img src="/forums/images/graemlins/kewl.gif" alt="" />