Voltage drop at idle

[moongdss]

Hey gang! Long time, no post

My 2006 base Vibe just had the OE battery replaced a few weeks ago after a few slow turn-overs. Autozone load tested and said it was done.

Fast forward to this week: I start my car, turn on the lights, then turn the a/c on and the lights dimmed. Hmmm! Alternator time?

I have the ScanGauge2 plugged in, so I look at the real-time voltage. It's reading 13.8ish mostly, until I turn the lights on (radio off, blower/compressor off), then the voltage dips to 12.4 at idle (it's back up to 13.8 when driving). Autozone tests it and says bad regulator... we order a new one.

My husband pulls the OE alternator and replaces it. It's still doing the same thing! Same readings, same light dim.

He has Autozone bench test the old alternator, and they fail it, then test it again and pass it?! They also tested the new one, and said fail, then pass. Husband thinks the guy just didn't know how to work the new tester. I'm thinking of taking it around to Pep Boys to see what they say on the bench test...

But wondered what else you guys think we should be checking.

Thanks in advance!
Diana

[Doug14]

If it just started doing it thats a bit odd. My 2006 has dimming issues, putting up more than one power window or turning on ac make my lights dim a bit, I know many other peoples vibes do similar things, I believe the main culprit it the weak alternator they use that simply cant keep up.

[moongdss]

Hmmm, I don't know if I should feel good that everyone's does this LOL! Thanks Doug This is what my husband was thinking was the case. Has anyone put in a 100 or 120 amp model? I'm having trouble finding one that's anything more than 80amps.

ETA: well, I found a 145amp here: http://www.maniacelectricmotors.com/1022112001.html" onclick="window.open(this.href);return false;
but I think this is overkill and would require some serious wiring/fuse upgrades. Anyone have experience with this alternator? I should pop down to the Electrical threads and hunt around

[Chiadog]

Hey gang! Long time, no post
Fast forward to this week: I start my car, turn on the lights, then turn the a/c on and the lights dimmed. Hmmm! Alternator time?
Autozone tests it and says bad regulator... we order a new one.
My husband pulls the OE alternator and replaces it. It's still doing the same thing! Same readings, same light dim.
He has Autozone bench test the old alternator, and they fail it, then test it again and pass it?!
They also tested the new one, and said fail, then pass. Husband thinks the guy just didn't know how to work the new tester.

Getting mechanical testing/advice from Autozone is like going to Walgreen's for a hysterectomy! Please see a qualified mechanic. One thing you could do and should always do for any unusual electrical problem is to physically check, remove, and test each and every fuse in the vehicle. Good luck.

[kumquat]

My first suspect would be a questionable ground point. I'm not familiar with the electrical system on the 06, but a good place to start would be to remove the battery's negative cable and main ground point and use a wire brush to clean up the steel and copper. If the ground cable itself is corroded replace it.

Looking at the diagram for the '08, it looks like there are two ground bolts near the battery - one to the body and one to the transmission housing.

[ColonelPanic]

^^ Good call on checking the ground points.

[moongdss]

I'll check the grounds this weekend! Thanks gang