Alternator trouble, I think

[yale]

I’m in Oakland having moved my car from NYC and while driving it up from Pioneertown, near LA, I noticed the alternator light staying on. Damn I thought, just when I don’t really need any issues. The light eventually went off and I gave thanks. But tonight driving around I noticed the interior car and head lights were super dim when I shut the car off making me think my battery is indeed not being charged.

So any recommendations for a shop in Oakland? Thank you all. My email by the way is yaluaka@aol.com and phone is 917-603-8678. Yale

[304065]

Yale,

Go on Amazon and buy an el cheapo cigarette lighter voltmeter (such as this: https://www.amazon.com/Car-Charger-S...auto+voltmeter) and plug it in and record the voltage:

1) With engine off, accessories off.
2) With engine running at idle; and
3) With engine running above 3000 rpm.

If the voltage is less than about 12.5 with everything off (I'm taking into account some voltage drop between the battery and the lighter) then it's discharging. The question is why, bad battery or bad VR, or bad alternator-something-else?

That's why we measure "2" - if it's not showing above 13V with the engine running slowly with the light off, then it's not charging at all; "3" is used to diagnose "something else" like bad diodes not putting out sufficient voltage once things are spun up.

[blucille]

Your signature seems to be missing a car (or 2).

[kentf14]

Reviving this OLD thread. Yale, hope you got things figured out.

So, I'm wondering what might be going on with either my VR or alternator.
I've had some sporadic issues with the dash warning light being lit up even with the car off and key out of the ignition. This would seem to be a bad alternator diode correct? The only thing is that this has only happened a few times and seem to be working otherwise.
The light is dimly illuminated at idle, but goes away when the revs come up. Previously it would be lit until I hit a threshold RPM then out altogether, but for a while now I've been getting the "dim at idle" symptom.

Measuring voltage at the fuse block in the engine compartment (top fuse) I get the following:

1) With engine off, accessories off. Don't have an answer for this yet.
2) With engine running at idle; 9.5 volts
3) With engine running above 3000 rpm. 14.9 volts

Thanks for any help!

Kent

[30westrob]

#2 9.5V is too low and indicates battery, low state of charge or battery is failing. I suggest charging.
#3 14.9V is too high, points to voltage regulator problem.

A great aid for trouble shooting is a digital volt meter that plugs into the lighter.