HELP, my charging light just came on and my guage shows about 10 Volts output.

[jeff]

My silver 88 formula.

 I checked and the belt seems fine.   any thoughts??...  on where to take it for repair,  I live near Grant Park,,,


Many thanks, jeff

[Roger]

Sounds like part of the diode pack (rectifier) in the alternator opened. Pull the alternator and take it to Advance Auto. They will check it for free. If yours is bad, get a re-manufactured unit...NOT a re-built unit.

BTW: Be sure to remove the Negative wire from the battery before you attempt to remove the alternator.

Forgot to add: The '88 has a Delco CS-130D alternator. Most GM cars use that now. You just have to be absolutely certain that the mounting piers match. You can clock any of them to match yours.

[fiero128]

Using a Multimeter measure the voltage of the battery when the engine running
it should be 13.8 to 14.4 volts
Like what was stated normally either the brushes or the diodes fail when the alternator fails.
There is a charging fuse that also fails.
Open circuit the charge voltage and the alternator volts climbs due to it being unloaded causing the alternator to fail