puzzling alternator problem Options

[jaybird840]

Trying to figure out a charging system issue I'm having. My alternator doesn't appear to be putting out any juice... 12.7 volts by multimeter coming from the battery with no key on. 12.5 volts with car running. Idiot light on the alternator appears to be working. If the idle drops under about 400 rpm, my gen light will come on (making me think the light's working as designed, I guess). Voltage meter in the console shows a flat 12v while running (drops to 10v with headlamps lit). All that said, is the voltage regulator internal or external on 'teeers ('75 1.8). If it's external, how can I test it. Best course of action??? Thanks all!!!

--jaybird (IMG:style_emoticons/default/headbang.gif)

[davep]

I agree with George.
Never trust the console voltmeter, only a voltmeter attached to the battery posts. Also test the voltage from the negative post to the fan shroud on the engine. There should be very little voltage (drop) on the ground circuit. If there is, try a heavy ground strap between the ground on the wall and the fan shroud, thus bypassing the body and the transmission ground strap entirely. The alternator is grounded to the fan shroud.