pizzabob

'96 4Runner, 3.4L -- 316K miles on original alternator. For the first time ever, alternator light came on for the last 20 miles of a trip last night. Everything was working perfectly, however. Battery is brand new, only a couple weeks old.

Today a hooked up a charger and it took about 15 minutes to achieve a full charge at 10A, which suggested to me that the alternator isn't putting out enough current to maintain the charge. I had been running headlights, radio, a/c, etc.

I went to AutoZone and they hooked up their tester, saying the alternator was only putting out around 15A when it's rated at 70 or 80A. He also mentioned that the voltage regulator was functioning properly.

Which brings me to my question to the esteemed members of this illustrious forum. A brush rebuild kit is available for under $10. Would you guys fool with that, or would you recommend replacing the alternator now without further delay? I'm thinking after 316,000 miles maybe it's time. Thanks kindly for your thoughts!

mt_goat

I've never done it, but this might help:
http://www.4x4wire.com/toyota/mainte...nator_brushes/

http://www.4x4wire.com/toyota/tech/alternator/

scuba

I'd do the brushes first, if you have the time that is.

If that doesn't solve the issue, go with an OEM Toyota alternator and nothing else.
The stuff from the auto parts stores is junk.

pizzabob

Thanks Mt Goat -- those were good links.

Since I originally posted, I found my missing Haynes manual and it has detailed procedures for testing continuity in the rotor, stator and diodes, as well as a minimum length spec for the brushes. So it looks like I should pop that alternator out and get busy with some testing and observation before proceeding.

My main question for the board remains this: Would worn out brushes typically result in the poor current (amp) output that the Zoneheads measured, or should I look elsewhere?

pizzabob

Thanks to you, also, Scuba.

I think your advice is probably good. That OEM Denso alternator on there now lasted 316,000 miles over 15 years, not bad.

I found one on the 'net for less than half the price at the local dealership ($122 vs. $250) -- same OEM Denso.

But I'll take a look inside the old one first... maybe can squeeze a couple more hundred thousand miles out of it, no??

pizzabob

Hey, wanted to follow up... removed the brushes and one of them was barely contacting the ring it bears against, and both surfaces were covered with black goop.

I cleaned the contact rings and replaced the brushes ($10 from a local auto electric shop), reinstalled, and have been cruising fine ever since. My alternator now has happy feet.

Thanks again to all who helped!