MustangEater82

So last 2 days I have had voltage fluctuations, talkin all the way into the low red and even had "Check Gages"(stupid canadians!) light go off, but then pop back up to what looks like 14V. Its enough you can see it with the headlights and such.

It is pretty random. If I WOT, it usually dips down to red. If I accelerate normal, and stay in each gear a little long, it seems ok.

I suspect a voltage regulatar issue. But the kicker is, the alternator is not that old. I bought the car in december. The seller liked to mention the alternator was new. It looks brand new new, along with the belt.


I had my wife revving around and got it to dip and pop up, with my multimeter. But its a digital ones, and they mainly take and average voltages, so its not the best for a test like this.

Seems like maybe its just slow of equalizing the alternator out.

-Took it to autozone, had the battery and alternator load tested, both checked good. Not even sure what there POS tester tests for.
-Battery is good, cranks and fires just fine, at crank, multimeter reads 10.5V so its good, its from 12/09.
-My positive battery was a little dirty, but I cleaned it up a little, wasn't that bad, and its still not perfect, but should be fine.
-negative was perfect
-Alt connection looked good
-I ohmed out a few of the grounds, like engine block to grounding points that were easily accesible, they were all pretty decent.



So... amy thoughts or tests I can do. I normally would just plop a new alt in but as said, this one seems pretty new. Curious if others have found other issues. I might start pulling cables and ohming them out and seeing if I have an internally corroded cable anywhere. I had one once on my 94 Camaro.

TGGodfrey

Where did the prior owner get the alternator from?

Autozone Alternator tests are just basic tests, not a guarentee but they catch the avergae bad alternators.

Autozone alternators are the worst you can buy in many cases. Its well known in the import world you avoid them at all costs. I got so tired of replacing the autozone alternator is my G/F 4 banger every month. After 4 warrenties I finally took a 130k factory alternator and threw it in.......going strong ever since and the warrentied alternator has become an emergency one.

One test you can do that I would recommend is to test the voltage drop over the positive lead from the alternator to the battery and on the ground of the alternator to the battery. How do you do that?

Using a Digital DVOM......... Positive lead on BAT stud of alternator. Negative lead on POS stud of Battery. Car running, Voltage on meter should be under .5V. If it's over .5V then you have too much resistance from alternator to the battery. Same testing with ground. Alternator case to Battery Ground stud and you want less than .5V. If those test good while the problem occurs and during normal operation I will suspect Voltage regulator failing.

Terry

MustangEater82

Good call didn't think of checking voltage drop. I was considering unhooking and ohming out sections of cables. Your way is better and checks same stuff through all Tue connections.

I have no clue what brand it is....

Any word on advanced auto alternators?, I believe I priced out Remy ones there.

Sent from my autocorrect butchering device.

n2ceptor

At idle is voltage reading 13.8~14.2???? If so, then it might be a slipping belt, since you stated loses volts at WOT...

Wore belt??? Bad tensioner??? Or regulator going out???

Gord's Green Z28

Which car is this on?

rv93

i agree that it sounds like your belt is slipping. or the harness that hooks up to the alternator is bad. that seems to break pretty easily if you yank on it. you could have a loose wire in there. check that.

MustangEater82

Camaro... and I am think its the tensioner, I could push down by hand... and its worse first thing in the morning it slips bad, but no screeaching.

Sucks because there are coolant passages and 11 year old plastic coolant elbows involved.