I've only noticed this recently. The previous owner claims that the alternator is new and, in fact, it does look brand new.

The problem is that when I'm idling at a light or parked, my heater will bog down a bit (you can hear the blower motor slow down) and the voltmeter and gas gauge will go down and up, respectively. If I'm stopped at a light with the blower on high, my volts will be at about 9. As soon as I tap on the gas even a slight bit, it raises to near perfect voltage, my headlights get a bit brighter and the blower runs to full speed.

Could this be the regulator? If so, isn't it in the alternator which is new? Also, why will my gas gauge go up (past full if actually full) when the voltage drops? It doesn't move at all like some Blazers I've driven (you take a corner or hit the gas and the gauge moves around)

Nick

 

If you only get 9v then either you have a bad ground, bad alternator, or bad battery. It is possible the alternator is new and is bad there are cheap ones, plus even the good onesa bad one makes it through. I believe the gas gauge is partly resistance based so the voltage may be changing how the sensor reads. The regulator is in the alternator you can get it tested at an auto parts store to see if its good. If it is then probably a corroded ground. If the gauge moves when turning or accelerating alot then the gauge may be going bad or somehow a baffle in the tank is busted allowing gas to smash around alot.