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!

[campbellcj]

Well my son had my/our multimeter with him at college so I borrowed one and poked around a bit over the weekend.

The alternator shaft/bolt does not have an allen hex which apparently is a tip-off that it "probably" has an external regulator, but I'm not certain of that yet. The regulator on the relay board looks (is) old and may not be hot but I haven't figured that out yet.

The battery (new) reads a steady 12.8V or so at the terminals. The dash gauge also seems accurate per the multimeter.

The new discovery is the issue seems to be intermittent as with the engine running around 1500RPM the voltage at the dash popped up to normal-ish briefly, a couple times, then dropped back to 10-11V.

Would that indicate the alternator brushes or the regulator or other? I had been figuring the regulator would just completely fail and not be intermittent but not sure of that either.