Battery acting strange??? - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 12 (permalink) Old Aug 21st, 02, 02:16 AM Thread Starter
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My 71 camaro has been sitting for about 1 month. I tried to start it and the battery was dead. I recharged it and is started fine. Two weeks later (not driving it during this time) it was dead again. I charged it again and 3 days later drove it to work.

My voltmeter read 15.5V while the car was going over 1500RPM and 14.5~15 at idle

This high of voltage tells me that the battery is really taking a charge from the alternator or the alternator is messed up. What is the correct way to diagonse my problem? Could a bad alternator drain a battery? I check at night to make sure none of my dash lights or interior lights was accidently left on.

Any help would be greatly apprechated. Also it has been very hot here in Ohio and that is why my camaro has not been driven. It is cooling down so it will be getting much more use.

This high of voltage tells me tha

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post #2 of 12 (permalink) Old Aug 21st, 02, 04:37 AM
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Had a similar problem with my 69 Corvette. I had a voltage draw that was causing the battery to go dead.
To find it I disconnected the ground from the battery, and connected a test light between the battery and cable. If the light is on there is a draw, the brighter the more draw.
Next I started removing fuses one at a time until the light went out and that was the circuit that had a problem. Then you trace the circuit to find out what is on it. In my case there was a light in one of the compartments behind the seats that was on, when the lid was closed. Hope it's that easy for you. Good luck.
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post #3 of 12 (permalink) Old Aug 21st, 02, 06:00 AM Thread Starter
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I will try that. How do you check a bad alternator?
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post #4 of 12 (permalink) Old Aug 21st, 02, 06:52 AM
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Try disconnecting the battery while the engine is running, if it dies could be the alternator.

[This message has been edited by ScottB (edited 08-21-2002).]
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post #5 of 12 (permalink) Old Aug 21st, 02, 07:56 AM Thread Starter
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The positive end or the ground? I thought all cars died without the battery connected?
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post #6 of 12 (permalink) Old Aug 21st, 02, 08:04 AM
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Remove the alternator and take it to, Pep Boys, Autozone, or any auto parts store that sells alternators they should be able to test your alternator.
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post #7 of 12 (permalink) Old Aug 21st, 02, 09:24 AM
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Don't 71's have a separate voltage regulater? Maybe that's the culprit. How old is the battery? Over 15 Volts it could be overcharging it and then it will want to boil if it gets too hot. Is the top wet? Check the water lately?

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post #8 of 12 (permalink) Old Aug 21st, 02, 09:29 AM Thread Starter
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I have had autozone and Advance auto parts both miss diagons a bad alternator in the past. I had to take it to a garage and they they found the bad unit. I would perfer to save myself some coin on this one.
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post #9 of 12 (permalink) Old Aug 21st, 02, 02:04 PM
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The battery may have an internal short. Disconnect it and give it a charge. Let it sit for a few days and then hook it up and see if it will start. Also, when charging with a substantial charger, the voltage should never exceed 16volts. If it does, the battery is 'sulphated'. I'm not technically certain what that means, but it is often caused when the water gets low and the plates become exposed to air. The end result is that the batteries internal resistance goes up. It acts like it will charge, but won't hold it. At 15.7volts it sounds like your battery could be sulphated. If you were charging with a small charger (i.e. less than 25 amps) I'd be even more convinced.

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post #10 of 12 (permalink) Old Aug 21st, 02, 02:49 PM
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Don't disconnect a battery lead with engine running. The alternator is capable of putting out over 110V. Without a battery connection the voltage can go crazy and fry anything electronic in your car.

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post #11 of 12 (permalink) Old Aug 22nd, 02, 01:35 AM
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Blk69, To clarify what ScottB is saying the battery drain test is done with the engine off and you use the ground side of the battery with a test light. Stick the point in the negative post and alligator clip on the ground cable (disconnected from battery). If there is a draw the test light will light up. If your test light doesn't light up, turn something on in the car to verify you are hooked up correctly.
The best way to test your battery is to have it load tested. We use a Sun VAT tester which is real nice and is all electronic. Capable of load testing the battery, checking the alternator on the car with the engine running, and starter testing. Checks the amperage output of the alternator which is really what you want to know and also checks the diodes in the alternator.
It is possible for a bad alternator to drain a battery down with the car sitting/engine off.
Going back to the test light for a drain on the battery. You may get a dim test light if you have a radio in the car that has a power wire for "memory" (station presets, clock, etc.). Shouldn't cause a dead battery sitting for a week, but could say sitting for a month.
I would first check for a draw, then get the battery tested, last thing, look at the alternator/voltage regulator.
Good Luck


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post #12 of 12 (permalink) Old Aug 23rd, 02, 02:34 AM
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IMHO if the alternator is completely out you will not be able to drive more than a mile or 2 before the motor pulls all the charge from the battery. Correct me if I am wrong here guys, but, once the car starts the alternator takes over and runs the components. You wouldnt need to disconnect the battery while it is running (old way to test alternator), the car would revert to the only other good source of power and drain the battery. I never took long to go dead in the water when I have had alternator probs before.
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