Paulyy

after driving 20 mins or so, is it normal for the alternator to drop to 12v (indicated on the factory volt gauge) ?

voltage reg is new,
new battery.
terminals cleaned
grounds cleaned.

Tiger03447

Dear Paulyy: No, it is not. the alternator should put out between 13.5 and 15.5 volts with a good battery...If you can locate an alternator rebuilder locally, he would most probably have a test bench...Pull the alternator and put it on his or anyone's test bench. It should show a voltage within the above stated range, and there should be a test for diodes and the regulator..Sounds like either one of two things is going on here..either a bad gauge or a faulty regulator...so..disconnect the gauge and direct wire it to your battery..record the voltage...the double check it against a diagnostic type of volt meter...that should give you some basis for a bad gauge.. You can also use a voltmeter on the output lead and the ground (car chassis) of the alternator while the engine is running at about 2K RPM...It should be in the spec range stated above...thanks, Tiger 03447

Paulyy

i had the alternator out. i have a new regulator in it. it got tested and producing 14.4v but i just think he put it on a machine and tested the voltage only.

I might hook up an aftermarket volt gauge to see if the factory one is playing up.

Thanks for the tips.

Jfrahm

One failure mode I have seen is that alternators test good under no load or light load but the voltage drops below acceptable under higher load (headlights, blower, etc.). They also get hot when producing a lot of current and can act up when hot but be OK when cool, that is difficult to bench test for.

rluciano

I don't trust the factory volt gauge on my 951 it reads 1.5-2 volts low, checked with a multimeter.

My wife's one owner '86 944NA reads accurately still.

I'd get out the multimeter.

Paulyy

I have my turbo timer that's been connected for a while, but i put the display back on that reads voltage. 14.1-14.2v standard at the moment. drops a little to 13.8 on idle.
battery is on 12.3v

When i give it a good drive on sunday, i'll report back.