Unknown power drain
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Junior User
Joined: Feb 2004
Posts: 93
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From: Oregon
Unknown power drain
Hello all - My 2000 F250 5.4L gasser is going through batteries and I'm not quite sure where to start the diagnosis. Here is what's going on:
- about 3 weeks ago I come out and the battery was dead, won't even take a charge. Everything was fine the last time I drove it.
- Put in a new battery. Had local tire shop to a charging system check - everything OK.
- Today, two weeks later, battery is stone dead, won't take a charge.
- The power locks have been acting strange for a few months - very sluggish.
- After I put the new battery in the power locks did not work.
I'm thinking the battery drain has something to do with the power locks - maybe a short somewhere.
Are the power locks on a fuse I can pull and still legally drive the truck? If I don't get the battery drain with the power locks disabled I'll know where to focus my efforts. Any ideas welcome. Batteries get expensive. Thanks
- about 3 weeks ago I come out and the battery was dead, won't even take a charge. Everything was fine the last time I drove it.
- Put in a new battery. Had local tire shop to a charging system check - everything OK.
- Today, two weeks later, battery is stone dead, won't take a charge.
- The power locks have been acting strange for a few months - very sluggish.
- After I put the new battery in the power locks did not work.
I'm thinking the battery drain has something to do with the power locks - maybe a short somewhere.
Are the power locks on a fuse I can pull and still legally drive the truck? If I don't get the battery drain with the power locks disabled I'll know where to focus my efforts. Any ideas welcome. Batteries get expensive. Thanks
Postmaster
Joined: Jan 2012
Posts: 2,693
Likes: 3
From: West of Chicago
I would check over all the grounds first making sure they are all clean and tight, replace if needed. Have your alternator removed and tested, Sometimes they will go bad causing a drain on the battery. You shouldn't have a problem driving with disabled power locks.
Veteran/Sheepdog
Joined: Feb 2012
Posts: 6,047
Likes: 110
From: Western AR
^^^what he said^^^
Bad alternator can mean it is starting to go, but hasn't completely kicked the bucket yet. If it is putting out less than 12.8 volts while at idle, it is a good candidate for the cause of the problem.
Bad alternator can mean it is starting to go, but hasn't completely kicked the bucket yet. If it is putting out less than 12.8 volts while at idle, it is a good candidate for the cause of the problem.
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Junior User
Joined: Feb 2004
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From: Oregon
Thanks for the ideas. I had the charging system checked. The alternator was putting out the proper amount of voltage with load and without. Could the alternator still be suspect? I'll check the battery ground.
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Junior User
Joined: Feb 2004
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From: Oregon
I'm still trying to figure this thing out. Today I disconnected the battery ground and connected my test lamp between the negative post on the battery and the ground strap. The test light lit-up bright which tells me there is a load draw somewhere. I removed and replaced fuses one at a time - the test lamp stayed on after each fuse was removed. 
I haven't cleaned the battery ground yet. If the battery isn't grounded properly would that cause a power draw? Thanks for any help.
PS - I also disconnected the large wire to the alternator but the test lamp stayed on.
I haven't cleaned the battery ground yet. If the battery isn't grounded properly would that cause a power draw? Thanks for any help.PS - I also disconnected the large wire to the alternator but the test lamp stayed on.
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Junior User
Joined: Feb 2004
Posts: 93
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From: Oregon
No accessories are plugged in. I haven't pulled each of the relays in the power distribution box yet to see if one of them is malfunctioning and drawing power. I'm surprised I didn't find the draw by pulling the fuses. It's probably something simple that I'm just not seeing.
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Hotshot
Joined: Oct 2003
Posts: 13,011
Likes: 742
From: Here in No. Calif
As crazy as this might sound, I have heard of the brake pedal pulling down, on its own, ever so slight but enough to trigger rear brake lights.
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Thread Starter
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Junior User
Joined: Feb 2004
Posts: 93
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From: Oregon
I decided to use my ampmeter to check the power draw instead of the test lamp. When I pull the fuse for the power locks the power draw is reduced. When I leave the fuse in and pull other fuses the draw stays high. I think the power locks are causing the power drain (they are currently not working) Maybe a relay switch? I'll do a search and start another thread for help if I need to. Thanks
Senior User
Joined: Nov 2011
Posts: 179
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From: Eastern WA
Agree with Papa Tiger, bad Gem Module could cause a draw down and affect your powerlocks. Some of the superduty's have had issues with water coming when it rains into the cab via the lower windshield seal and it runs down around the Gem module and causes havoc. New ones aren't cheap but a good shop should be able to test it I believe.
Not saying this is it, but could be.
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Junior User
Joined: Feb 2004
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From: Oregon
Thanks for the suggestion. I'm pretty sure it's something in the door lock circuit. When I pull fuse 26 under the hood the power drain stops. It's weird, when I plug the fuse back in both locks slam closed. It's like they get an initial power surge. Later, when I push the button to open the lock I can hear the actuator motors trying to work than they quit. It makes me think the actuators will work if they have enough power; it's being drained off somewhere. Could both actuators go bad at once and if they did would they cause a power drain or just not work? Would other accessories be affected if the Gem module was going out? Other than the locks, everything else is working OK. Diagnosing auto electric problems is frustrating 
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Junior User
Joined: Feb 2004
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From: Oregon
I don't think I have a remote entry module I bought the truck used from a private party; it didn't come with a fob. I suppose I could still have a remote entry module. How would I know?
I bought the truck used from a private party; it didn't come with a fob. I suppose I could still have a remote entry module. How would I know?