So I finished my motor swap and noticed that my voltage gauge on the dash is reading lower than it use to with my old v6, at first start up the gauge is sitting at the halfway mark on the gauge, but Iv noticed that as I rev the car of an moving the gauge increases to the mark before the red, all my lights brighten up, but when I'm idling the gauge comes back down and the lights re dim, is this normal? I got alittle scared this morning when I was taking it to school and I had my lights on and came to a stop light, the gauge dipped below the half way mark, my lights got really dim and stayed like that till I started moving again? Is this a sign of a bad or to weak of an alternator, or a bad battery? Are these normal things?

 

not normal,sounds like you have a faulty alternator-did you reuse the one off the v6 or get a different one?

 

no I got a different alternator because my v6 alternator was too big. Not sure what alternator I have, I got it from my uncle who runs a scrapyard/ junkyard, he said it was working and it fit the size and pulley requirements that I needed.

 

If you're able take it into an AutoZone or Oreilly Auto Parts. Either one can test it for you. The AZ here does them oncall. Oreilly's have a machine to bench test it. I always have them check even the new ones I buy before I install to save myself time and money (I'm in an rural area).

 

the alternator your uncle gave you is probably a 10si type-very common on lots of 1973-82 GM cars,comes IIRC,in 37,42 and 63 amp ratings.Yours probably has a bad connection to the stator or possibly a bad diode or two causing the weak output at low RPM. See if your uncle has another one to try It is also possible there is a bad engine ground or other problem causing the low idle volts,but bad alternator most likely.