Originally posted by Turbo Brian
13.3 at the battery with the engine running is in the normal range for these cars. These seem to run less than the 13.8 to 14.2 volts that many GM cars run. If you insist on changing the voltage regulator, the regulator on this model runs about $50 just for the part. It is also soldered to a mounting connecter, so that adds one more step to the part swap process.
If your car starts normally, then the alternator is charging your battery at least most of the time.
The brown wire coming off of the back of the alternator connects to the back of the instrument cluster and excites the alternator field through the volt light. If there is a loose connection at any point between the back of the alternator through the volt light, then that may be causing your intermittant volt light. If this is the case, you can rewire or if you choose not to, get a field fix harness from Casper's Electronics. This is a plug and play fix that works around wiring harness problems.