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Will a bad alternator drain my battery??

Old 10-03-2006, 11:10 AM
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Default Will a bad alternator drain my battery??

Well, I just installed a AC Delco alternator because my other alternator was not charging my battery while my ac was on at idle. So I went ahead and installed the new one and now it drains the battery pretty quick. I have a volt meter and tested the battery 12.89 volts. When I hook it up to the car and turn it on I see the volt meter go from 12.89 to 9.02 within seconds. So like the title states can a brand new alternator drain the battery that quick or do I have a short somewhere?? One other thing I would like to mention is that this was my first time installing an alternator with the d-1. I had to push the fan up while taking off the d-1 so I'm thinking I might have moved a wire or something what do you guys think. Any comments greatly appreciated...
Old 10-03-2006, 11:17 AM
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If it is a reman. alt they mabey. If for some reason the field is still energized after you turn the key off it will bring the battery down.

For obvious reasons your battery will lose charge while your driving if the alt is not charging at all.

Check your connections at the ALt. make sure that the main red power wire on the back of the alt is tight and not shorting out on the alt case anywhere. Mabey when you tighten the nut the wire moved and is too close to the case or is shorting on the case due to slight vibration of the engine while its running.

I don't think you should have changed it to begin with. I think most LS1s on here have less that 13 volts @ idle with the A/c on. Check your owners manual, I think it says something about that in there. I know my car is the same way with the A/c on but as soon as you crack the throttle the voltage comes right up.

You might want to try doing a search on here about your low voltage problem with the A/C on

BTW the proper way to test a battery is to load test it. Checkin voltage at the battery will only tell you if the alt is working (if the car is running)

Last edited by LilSlo1; 10-03-2006 at 11:23 AM.
Old 10-03-2006, 11:35 AM
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Originally Posted by CrawlinRS
If it is a reman. alt they mabey. If for some reason the field is still energized after you turn the key off it will bring the battery down.

For obvious reasons your battery will lose charge while your driving if the alt is not charging at all.

Check your connections at the ALt. make sure that the main red power wire on the back of the alt is tight and not shorting out on the alt case anywhere. Mabey when you tighten the nut the wire moved and is too close to the case or is shorting on the case due to slight vibration of the engine while its running.

I don't think you should have changed it to begin with. I think most LS1s on here have less that 13 volts @ idle with the A/c on. Check your owners manual, I think it says something about that in there. I know my car is the same way with the A/c on but as soon as you crack the throttle the voltage comes right up.

You might want to try doing a search on here about your low voltage problem with the A/C on

BTW the proper way to test a battery is to load test it. Checkin voltage at the battery will only tell you if the alt is working (if the car is running)
One of the other reasons I changed it was because when I got into boost right around 6000 rpms I would loose power causing my fuel pressure to drop dangerously low. I don't think the alternator is a raman beacuse it came in a ac delco box which appeared to be new. So maybe a wire is shorting out somewhere because I tried another battery and it did the same thing. What do you think???
Old 10-03-2006, 11:48 AM
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I'd start checkin wires then.
Old 10-03-2006, 12:01 PM
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Get your car scanned. The most common code you'll get is P1637 and it won't throw your check engine light. If it does show up in the scan replace the plug on top of the alternator. You can get a new one at your local dealership. They will give you one that has four wires, just cut what you don't need and it only cost about $35. Also, did you recharge your battery when you switched the alternator??
Old 10-03-2006, 01:43 PM
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Originally Posted by Dmoney
Get your car scanned. The most common code you'll get is P1637 and it won't throw your check engine light. If it does show up in the scan replace the plug on top of the alternator. You can get a new one at your local dealership. They will give you one that has four wires, just cut what you don't need and it only cost about $35. Also, did you recharge your battery when you switched the alternator??
No I didn't charge the battery I did not know I had to the battery had a full charge.
Old 10-03-2006, 01:54 PM
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One other thing when I was moving around things in the engine bay I moved/pulled aside a square looking box with wires leading into it. I'm not at home right know, but I believe it's on the drivers side right by the radiator. Can someone tell me what that is and is there any wires that might be causing a short since I pulled it a little further out.
Thanks again...


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