Battery not charging, no battery indicator light.

[alm001]

I've had a problem over the last two weeks that I initially thought was my battery.
The car started to crank slowly one day, but it drove fine. The next morning it also cranked slowly so I relegated myself to buying a new battery, and drove it to work anyway. Started (slowly) for the ride home, but I stopped at the bank after the 20min ride home. Leaving the bank - stone dead. I charged it over the weekend, and the battery held 12.7+v in the garage. I drove it Tuesday and it seemed normal. I went to start it today and it cranked slowly again. I popped the cover, and put a meter on the terminals and it was showing 12.5v with the car running at idle. I didn't bother the wife with revving it up to check, and I just parked the car to deal with later. Never had a battery light come on.

If we can assume that alternator/regulator is bad, I have options;
-Get a whole alt ~$220 with a new belt
-Get a voltage regulator ~$40 (90 with a new belt)
-Get a voltage regulator and do an underdrive pulley while I'm in there. (Comes with new belt) ~$220 total

Any more tests I should run? What are the chances I change the regulator and the whole thing is bad?

Has anyone used the "Synamas Products Group" UD pulley from ebay?

[algiorda]

I didn't see the "Battery" on your list. How do you know it's holding a charge? How old is it?

[alm001]

Originally Posted by algiorda

I didn't see the "Battery" on your list. How do you know it's holding a charge? How old is it?

I had charged the battery over a couple days, and then let it sit for a couple more days. The voltage held steady in the 12.7 / 12.8 range, connected to the car.

[algiorda]

http://986forum.com/forums/general-discussions/66230-battery-drain-after-1-week.html

[AZ986S]

Sounds like your alternator is bad.

I cooked my alternator at the track his winter.
The ECU was still working with the voltage down to 11.5 volts, but ABS was not liking the low voltage.

I put in a rebuilt alternator and got lucky. It has held up.
I also had previously installed the UD pulley from Tarrett I believe and I have not had any issue related to the UD pulley (like low charging, low coolant flow, power steering etc...).

[Steve Tinker]

Originally Posted by alm001

I've had a problem over the last two weeks that I initially thought was my battery.
I popped the cover, and put a meter on the terminals and it was showing 12.5v with the car running at idle. I didn't bother the wife with revving it up to check, and I just parked the car to deal with later. Never had a battery light come on.

With the engine running above 1000rpm, you should see a 13.5 - 14.2v (depending on the battery state of charge) @ the battery terminals. Anything lower than that and the charging system is suspect.

Deciding if the problem is a faulty alternator or a voltage regulator will require a bench test of the alternator.

[Gelbster]

Don't overlook the infamous "Y connector" and corrosion under the insulation of the battery cables.Search has more.I linked a Bosch Alternator rebuild video recently.UD pulley gets mixed reviews.

[alm001]

Originally Posted by Steve Tinker

With the engine running above 1000rpm, you should see a 13.5 - 14.2v (depending on the battery state of charge) @ the battery terminals. Anything lower than that and the charging system is suspect.

Deciding if the problem is a faulty alternator or a voltage regulator will require a bench test of the alternator.

Last night I had to move the car so I put the meter on the windshield and revved it up 1k, 3k, 4k... doesn't matter 12.xx V

I heard pepboys/autozone can't bench these alts. Is that true?

Originally Posted by Gelbster

Don't overlook the infamous "Y connector" and corrosion under the insulation of the battery cables.Search has more.I linked a Bosch Alternator rebuild video recently.UD pulley gets mixed reviews.

I recently did my heater core and removed the battery for access, all the cables are clean and appear to be in good shape.


I had to drive the car to work today (long story with backup car) and we're down to 11.9v running when I arrived.

[Gelbster]

So what else is on the 'while you are in there' list ? Pullies,w/p .belt,check the vac reservoir for cracks?

[alm001]

Current state of affairs:

[particlewave]

This is almost certainly a voltage regulator. The brushes and bearings can go bad on an alternator, but it is much more likely to be the regulator.
There is nothing special about these alternators, so any shop that can test charging systems can test it for you.

Get it fixed before you kill your new battery.

[Lapister]

Just went thru this too. Oreillys can test on the fly and give you print out whether it's good or bad. In my case both were bad battery/regulator. Many forget that even a close to dead battery can show over 12 Vdc, imagine a thin wire will conduct voltage but it's the Amps that make things happen in cars. Regulator definitely suspect!

[alm001]

I had my battery charged by a battery shop while I waited for my regulator to come in. I got it all together last night and we are back to functioning 100%

Installed voltage regulator - fixed problem, solved.

[Gelbster]

Note that Particleweave gave the correct diagnosis in #11 above. Well done.