Battery Draining
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Senior User
Joined: Apr 2003
Posts: 103
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From: PA (Outside Gettysburg)
Battery Draining
The battery in my 79 F150 keeps draining. I replaced the battery, woke up and it was dead. Charged it that day, next morning dead again. If I jump it, I can drive it, but after sitting 8 hours or so, no juice.
Alternator?
Alternator?
Postmaster
Joined: Apr 2000
Posts: 2,838
Likes: 6
From: SD
It could be anything. This is how I find it. Disconnect the negative batt cable and use your test light with one end on the batt cable and other end on batt terminal. If there is a drain it will light up. Now disconnect the wires on alt, if light goes out you've found the problem. If still lit, start pulling fuses (one at a time) and check that light goes out - don't forget to close door when checking light, dome light will make the test light light up. When you find a fuse that makes the light go out, then you know what circuit the draw is in. Now find out what the fuse runs and disconnect each one of those things (with fuse in) for the light to go out, then you've found the draw. Then repair/replace the part as needed and check for draw again.
It takes a while, but it gets to the bottom of the problem.
The most common draw sources I find are: bad alt, bad radio, brake lights on, dome light on.
Some times a battery will have an internal short and won't hold a charge, but if it's the battery, the test light won't light up at all, because there's no draw.
Marty
It takes a while, but it gets to the bottom of the problem.
The most common draw sources I find are: bad alt, bad radio, brake lights on, dome light on.
Some times a battery will have an internal short and won't hold a charge, but if it's the battery, the test light won't light up at all, because there's no draw.
Marty
Elder User
Joined: May 2003
Posts: 967
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From: Southern NJ
Great procedure, 73, very thorough. He said he's got a new battery, so that Shouldn't (love that word) be the problem. I had the voltage regulator draining my battery once, had arced on the inside and was dumping through the housing of the damn thing. Figured that one out completely by accident, put the test light on the rad support for a second while I undid a wire on the alternator and when I looked up noticed a slight glow. Too weird, lol, only on my trucks, I swear. 
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
All,
He claiming the battery is going dead ove rnight. This leads me to believe that it is something larger than a hood/glovebox light. Check the voltage regulator. Its got coils/relays that could stick. Power antenna is the one that i used to always see. Not on a Ford truck though?
Good Luck,
KingFisher
He claiming the battery is going dead ove rnight. This leads me to believe that it is something larger than a hood/glovebox light. Check the voltage regulator. Its got coils/relays that could stick. Power antenna is the one that i used to always see. Not on a Ford truck though?
Good Luck,
KingFisher
Mountain Pass
Joined: May 2001
Posts: 246
Likes: 0
From: MT
Just had this problem myself but it would drain the batt. in an hour..Replaced the volt reg. and no more problem..
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Freshman User
Joined: Oct 2003
Posts: 26
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Had that problem on my 79. drove me nuts for a couple of weeks. Replaced regulator, no help. Finally traced it to the gas tank switch on the frame. I had flipped the switch and I guess it stuck. Rear tank has not been used in years. Why this circuit is hot even when the key is off is anyones guess, poor design.
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Thread Starter
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Senior User
Joined: Apr 2003
Posts: 103
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From: PA (Outside Gettysburg)
Update on Battery Drain
OK, I took 73Customs procedures. Started at the fuse box, since Alt was brand new. Rolled through fuse box and test light never went out.
Disconnected Alt wires and out it went. I'm going to go to Pepe Boys during lunch and have them test the Alt.
What if it test good. Regulator? Would the test light go out when Alt disconnected if it were the regulator?
Thanks.
Disconnected Alt wires and out it went. I'm going to go to Pepe Boys during lunch and have them test the Alt.
What if it test good. Regulator? Would the test light go out when Alt disconnected if it were the regulator?
Thanks.
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
All,
Yes, It would.
Reconncet your alt.
Try disconnecting your voltage regulator and see if the light goes out. I bet it will!
The Alt. is not fused through the fuse bo
Too much current).
Your almost done!
KingFisher
Yes, It would.
Reconncet your alt.
Try disconnecting your voltage regulator and see if the light goes out. I bet it will!
The Alt. is not fused through the fuse bo
Too much current).Your almost done!
KingFisher
Thread Starter
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Senior User
Joined: Apr 2003
Posts: 103
Likes: 0
From: PA (Outside Gettysburg)
Took the Alt in to be tested, man was it HOT. Was only putting out 6Volts. The exchanged the Alt, and I bought a new Regulator.
So far so good, I'll check in the morning. Although I'll say that after putting new alt and regulator in, I pulled the battery cable and put test light on....no Draw so I'm happy....for now. Think I blew the radio fuse though.
Thanks for all the help.
So far so good, I'll check in the morning. Although I'll say that after putting new alt and regulator in, I pulled the battery cable and put test light on....no Draw so I'm happy....for now. Think I blew the radio fuse though.
Thanks for all the help.