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tiorunder
User
May 28, 2008, 4:20 PM
Post #1 of 6
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Battery keeps going dead
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Hey !! Great forum.
I am a newbie with an old problem. Got an '85 Chevy C-10, 305, TH350.
Problem: Installed 2nd new battery, but it keeps going dead. Something is drawing from the battery as the truck sits in my garage.
Question: How do I isolate the culprit circuit/accessory/whatever that is killing my battery ??
Thank you in advance
Tiorunder
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 28, 2008, 5:39 PM
Post #2 of 6
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Re: Battery keeps going dead
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I think alternators can do this with these.
Way to check ----- put a test light between disconnected battery terminal and the cable. With a drain it will light up if drain is enough to kill the truck overnite. Pull fuses one by one until light goes out and at least you've narrowed the search to that circuit. Is there anything unfused installed on this truck or not run thru main fuse box?
If no success try disconnecting the alternator itself - protect the wires with that test....
T
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tiorunder
User
May 28, 2008, 7:35 PM
Post #3 of 6
(3809 views)
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Re: Battery keeps going dead
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Hey there Greenleaf ! Thanks for the quick reply.
I did much of what you said to do and I didn't get anywhere definitively. First thing I did was give the battery a GOOD charge. Next, I put a test light between the negative battery post and it's cable and it did not light up, however, it DID light up when I connected the light between the positive battery post and it's cable, which leads me to a brand new question:
Which battery terminal should I use to connect the light to make this test ???
With it connected at the positive terminal I pulled EVERY fuse, one at a time, but to no avail (the light stayed on).
I also disconnected the alternator itself during this test and the test light stayed on.
If I was supposed to connect the light at the negative terminal (as I am beginning to think), then I would assume there is nothing drawing from and draining my battery since the test light did not illuminate.
I am beginning to suspect my alternator. I put a digital volt meter on the battery while the motor was running and it did not read any more than battery voltage (12 volts). Shouldn't it have read 13 or 14 volts?
HELP!!!!!!!!!!!!!!!!!! and thanks again !
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2008, 1:21 AM
Post #4 of 6
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Re: Battery keeps going dead
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I'm probably suffering from advanced memory loss but the test should work from neg bat post to the disconnected neg cable - try that and turn on something and test light will light or open door with interior lights trying it will light the test light. I just don't know what happens pos to pos cable as I don't try that and that just might light up for another reason.
The alternator on this 85 Chev PU should have the regulator inside it which can be serviced but I doubt this alternator is that expensive now. It should be putting out closer to 14 volts with engine running not much under that with nothing else electrical running.
You said you only see the 12v with it idling and that alone show a problem. Go ahead and idle again and turn on headlights, blower fan on high, radio and watch it drop below the 12v - it will. That's what's killing the battery - it can't replace even the power needed to run engine never mind any accessories and charged for a restart.
I don't want to waste YOUR money but I'd put an alternator in now from the observations. Whole replacement or if you want to take it apart you can but it's probably not worth it....... there are a few items that go wrong, regulator, brushes, and diode trio.
If you bring in old alternator many parts stores can test them off car for you which rules out most mistakes of replacing a good part.
I'll check how much a new alt is in a second and see what they cost now and post that,
T
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2008, 1:36 AM
Post #5 of 6
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Re: Battery keeps going dead
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   Valucraft / Alternator
Warranty - 1 YR 7127 Price: $34.99  Core: $15.00 Total: $49.99 Application: Without A/C Note: 63 Amp Remanufactured
______________________________________
There are a few and this one was cheapest. It is ok IMO to use this instead of high amp output ones if the same size and connections. High amp output alts just are overkill unless you specifically need that power for something added to the truck. The alt could be "clocked" differently with or without A/C - the store should change that for you to preserve warranty but then again I bet stores won't do that anymore. Clocking is just the position the plug will point for the harness connection. Granted - if you pull it apart while doing that the brushes fall out and would have to be re-assemebled so they don't want you to do that AND keep the warranty. It's NBD if you get a used one and need to - just ask again I'll explain,
T
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tiorunder
User
May 30, 2008, 3:53 AM
Post #6 of 6
(3791 views)
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Re: Battery keeps going dead
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That was it. I put an alternator in the truck and the problem is solved. Thanks for your time and advice.
Tiorunder
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