hey guys been trying to track down this problem for awhile now and hit a wall. see when i have my headlights on and heater going the voltage on my gauage just drop down bad barely on the normal side. then when i turn on my blinker it fluxes. i had the ALT and battary check and they said it was charging just fine. right now im guessing its a ground issue. and just to add in the other day i was sitting at idle around 600RPM and sometimes my rpms and voltage would drop together and come back up.

 

Lights are a pretty big draw on power. It seems to me that the alternator is on its way out. I would check it with a meter to see if it is in parameters. Better yet, I have an electrician friend that would check it for me, I'm not that good at the electrical stuff.

Probably someone else will have a better idea.