voltage dropping in traffic, bad alternator?

[cockerpunk]

ever since i installed the new lower temp fan switch, my voltage on instrument panel has been around 12 volts. yesterday i got stuck in traffic, no biggie, temp stayed fine, never about 85C ... really great actually.

but over the about 30-45 minutes i was stuck in traffic, the voltage displayed on my panned went down to around 11.

on my way home, not in traffic, even with headlights on, fan and radio on, popped back up to 12 or about 12.5.

going bad alternator?

[campbelljj]

Order replacement voltage regulator brush set. Paragon and host have these in stock

[Rasta Monsta]

Originally Posted by campbelljj

Order replacement voltage regulator brush set. Paragon and host have these in stock

. . .but brace yourself for new alt if regulator doesn't fix it.

[cockerpunk]

sounds like the voltage regulator is on or right near the alternator. worth replacing both at the same time? also looks like a new alternator from pelican comes with a voltage regulator. makes me think its more worthwhile to just replace the whole thing.

[TrailRider]

Oddly (must be the warm weather) but I just had the same issue so interested in this post... Driving home from work last evening my voltage dropped to 11 (normally at 12.5). I had the AC / Radio on and it was warm out - 95 degrees F. The radiator fan was running very frequently... turning off AC didn't seem to help.

Will look in to replacing the voltage regulator...

Thanks!

[pfarah]

I had a similar issue and first replaced the regulator as it's mounted inside the back end. After messing around with that for a while, I simply replaced the entire alternator assembly and haven't looked back. The unit appeared to be original with emerging bearing noises so I'm better off...

Some parts sources provide a one year warrantee with their Bosch Refurbished alternators.

[DannoXYZ]

Alternators pretty much never go bad. In some rare cases, the slip-rings can wear. Most of the time, it's pretty much always the VRM going out or the brushes wearing. Replacing the VRM takes care of both issues. Doesn't take that much effort to remove the alternator to replace the VRM. Get the adjustable one Transpo # IB372A. You can set to around 14v for brightest headlights (about 13.5v at bulbs) and charge the battery to full capacity.

[curtisr]

[Lapkritis]

Check the brushes first. This is common when they're near end of life and a gap forms where they contact the rotating shaft. Higher rpm can bring them back to life whether it be through vibration or suction. Avoid generic regulators/brushes. Those bits are tempting at 1/4th the Bosch price but they last 1/10th as long... Very soft brushes on the generics.

Would also recommend cleaning battery post contacts and checking battery service level.

[hpaulb]

Was fighting this problem for a long time and ended up with a silly fix. Belt always felt tight. At least the same as every car i do. Was always running off the battery and never charging. If the pully spins withount noise and no side to side movement. Bearings are good. Replace the brush assembly. Get them locally at any alternator place. I got mine at the local parts guy. Common Bosch part. Cost me $30 and two minutes to put it in. Final result was to tighten the belt more. All is good. Replace belt if worn or feels to smoth.