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Join Date: Sep 2013
Location: West Boca Raton, FL
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Bad Alternator Battery won't die?

While my '88 924S was at my mechanic for new ref sensors, on the test drive they say the car stalled out on them. They pulled it back to the garage and say the alternator reading was all over the place. 9, 11, 12 , 9 .....Says the connections to the alt are good and the belt is new and tight properly. That I need a new alternator.

I ordered an alternator to be delivered. They charged the battery and I picked up the car on Friday ( 5 days ago) and drove home. 15 miles no issues. I charged the battery overnight at home.

Saturday morning I went to Advance to test the battery and alternator and battery was 12.52v 815 CCA but the alternator results were No Voltage.

So Saturday, Sunday and Monday I drove the car on short runs maybe 15 miles per day.
Saturday the results were about the same at Advance.

Today I drove about 10 miles today and back to Advance for test, and battery 12.70v and 787CCA. Alternator No Voltage.

So this is approx 55 miles and 4 days after my overnight charge and the battery keeps testing good and the car so far, starts right up each time.

It's great I have a good battery but can something be going on other than me having a bad alternator bcs I figured I would have a drained battery by now? Any suggestions are appreciated.
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.

Last edited by Austin87; 01-30-2018 at 10:18 AM..
Old 01-30-2018, 10:12 AM
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are you continuously top-off charging when you get home?
just on battery you could probably drive an hour or more in one stint (50+ miles highway) before the charge gets too low.

is the little blue wire hooked up to the alt?
Old 01-30-2018, 10:40 AM
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Turn your headlights on to see if the battery is really good...

Carry a cell phone to call a tow truck.
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Old 01-30-2018, 11:20 AM
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I haven't topped off the charge at all since the overnight charge on Friday night.
Hard to see the wiring but from under the car it looks like there is a blue wire wrapped with other wiring that connect to the alternator. As my mechanic says he checked wiring I have to figure the blue is connected too.
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.
Old 01-30-2018, 11:29 AM
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Quote:
Originally Posted by 944 Ecology View Post
Turn your headlights on to see if the battery is really good...

Carry a cell phone to call a tow truck.
Right after you drive into a tree to see if your bumper works.
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.
Old 01-30-2018, 12:39 PM
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I've read about an excitor wire and a light bulb that has to be a good bulb, but never heard of this before.




..
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.
Old 01-30-2018, 01:04 PM
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Austin87:

You might take a look at your voltage regulator. This sounds to me as if the brushes are worn and need to purchase a new VR.

Just a thought.

Hope this helps.
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Old 01-30-2018, 02:25 PM
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key on, engine off should give a warning light. if not, your harness may have been jostled while the sensors where renewed

I suggest purchasing a volt/ohm meter and rebuilding your alt with quality parts. its about $50 bucks for an OE regulator and not-china bearings.
Old 01-30-2018, 03:02 PM
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I have been using the Huco regulators, they are reasonably priced and so far have worked well for me. They can be changed with a stub screwdriver and the alternator in the car. Yes if the alternator also needs bearings these can be changed as well (or repacked if they are still good, but old) but that's a lot more work.

The higher quality Chinese bearings have been fine for me, not sure what bearing are still not made in China. But not everyone can press out alternator bearings.

I agree that it sounds like the voltage regulator or brushes are going out and it's barely getting by. Testing with the headlights on is a good idea IMO.

Battery voltage before you start (12.6v+)
Battery voltage after you start (14-ish, charging)
Battery voltage during normal running (13-14v)
With the lights and heater on, etc. it should stay above 12.6v

If it's low, chances are it's the voltage regulator/brush assembly. Brushes are even easy to replace if you really want to save a few bucks and have a soldering gun. The voltage regulator is common enough, this Hella would work IMO: HELLA 004241151 it's under $20 Amazon Prime.
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Old 01-31-2018, 04:20 AM
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Hit it with a crow bar the brushes are worn. Get a week out of it. If it's a Bosch you can just change the regulator, it includes the brushes. My PN is 30062
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Old 01-31-2018, 12:54 PM
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I can pick up a new Kaehler Voltage reg locally for $20. tomorrow.
I'll try this and hope it does the trick.

( My Red dash voltage light does come on with the key on accessory position.)

I guess it's easier to get to the screws for the regulator from underneath vs above.

Thanks for the input.
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.
Old 01-31-2018, 01:42 PM
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Just got the newalternator today. However I have been driving 20 avg miles per day, no issues. Last two nights I drove with headlights on and stereo on maybe 15-20 miles and still had no issues with car dying on me. When I topped off the battery with my charger the next mornings after night driving the battery barely needed any charge. Maybe 2 amps or 30 minutes to get back to full charge.
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1988 Porsche 924S - On the road again after 3+ years.

Dodge GC ES 278,xxx and counting.
Old 02-08-2018, 10:23 AM
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Any voltage readings or just guesswork?
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Old 02-08-2018, 04:15 PM
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