Alternator troubles

[Rory535i]

Recently the battery light on my dash has started glowing extremely faintly, almost impossible to see untill in total darkness. Obviously this is starting to affect the performance of the battery. Problem is, the light only comes on sometimes. When the light is on, the voltage output of the alternator is reading 12.05V and when it's off it's reading around 13V give or take a bit. Could this be a fuked voltage regulator or does the alternator just need a rebuild? cheers.

[Kai@e34.de]

worn carbon brushes i guess

[SRR2]

With gradual degradation like that it's probably brush wear. It could also be a diode going bad or the regulator IC. You can replace the regulator and brush assembly, but if I were going to the trouble of accessing the alternator for this work, I'd probably just stick in a new rebuilt alternator if there's a lot of miles on the one that's failing. A rebuilt alternator will get you new bearings, slip rings, brushes, and regulator.

[Dash01]

If you're semi-handy with a soldering iron, you can replace the brushes for about $3, by removing the regulator from the back side of the alternator. Disconnect the battery first, keeping in mind that you'll then need the radio anti-theft code upon re-connection.

Or, while you have the regulator out, just replace it for ~$13 at NAPA for a knockoff, or several times that for a Bosch original from BMA.

I replaced my brushes and put the old unit back in about 15 months ago, with no ill effects. I keep a NAPA knockoff regulator in the glove box, as a backup.

[Scott C]

If you're semi-handy with a soldering iron, you can replace the brushes for about $3, by removing the regulator from the back side of the alternator. Disconnect the battery first, keeping in mind that you'll then need the radio anti-theft code upon re-connection.

Or, while you have the regulator out, just replace it for ~$13 at NAPA for a knockoff, or several times that for a Bosch original from BMA.

I replaced my brushes and put the old unit back in about 15 months ago, with no ill effects. I keep a NAPA knockoff regulator in the glove box, as a backup.

Not to divert the thread, but did NAPA have the brushes?
Thanks,
Scott

[Rory535i]

Thanks. I'll get hold of some brushes and whack them in.

[Dash01]

Pretty sure it was NAPA that sold me the brushes, but they're pretty common brushes and probably can be bought from a hardware store, electrical shop, etc..

I used the old springs, which had plenty of strength, esp. when fully compressed on installation of the new brushes.

And, did not bother to contour the brush tips, since the alternator shaft acts as a lathe and does that when the brushes are installed.