Testing -6 alternator/regulator in car?, Yep I tried searching but maybe I suck at that... Options

[campbellcj]

Hi All -

I'm fairly sure my alternator (-6) just crapped-out and want to confirm that's the problem. Very abruptly my dash voltmeter dropped to around 10-11V when running, regardless of revs, vs the normal 13.8 or whatnot.

The battery did not seem to be charging, but was just about 5 yrs old so I replaced it, however no change in the voltmeter reading. All wiring and grounds look intact, same as before the issue started. The car starts and runs normally with a charged battery.

Is there an easy way to confirm it is or isn't the alternator with the engine still in the car?

Thanks!

[troth]

Hi All -

I'm fairly sure my alternator (-6) just crapped-out and want to confirm that's the problem. Very abruptly my dash voltmeter dropped to around 10-11V when running, regardless of revs, vs the normal 13.8 or whatnot.

The battery did not seem to be charging, but was just about 5 yrs old so I replaced it, however no change in the voltmeter reading. All wiring and grounds look intact, same as before the issue started. The car starts and runs normally with a charged battery.

Is there an easy way to confirm it is or isn't the alternator with the engine still in the car?

Thanks!

Have you verified the gauge reading with a multimeter on the battery? Is the alternator light on? Belt tensioned?

Referencing a Bentley manual for my 911:
After verifying that your belt is tensioned, electrical connections good, etc
Connect voltmeter to battery
Run engine at ~1500 rpm and check voltage
Voltage much higher than 14.2 = bad regulator
Voltage below 13.5 = bad v-belt, regulator, or alternator….
…Assuming your v-belt is good continue running at 1500 rpm and turn on all electrical accessories. If voltage stays the same most likely cause is the regulator. If voltage drops most likely cause is the alternator.

I think this is a quick and dirty test you can do at home. Alternatively you can go to any FLAPS and they will have a tester that works on similar principles.