I have an 07 f150 5.4L super crew. I came out one morning and the battery was dead. I jumped it, and drove it for a while. Came out the next morning and it was dead again. Had the battery tested... no problems, but changed it anyway with a good NAPA battery. Its been a month now, and i let the truck sit for 4 days, and the thing is dead again. I had autozone put the tester on it, charging system is good, and battery is good. WHY IS MY TRUCK DRAINING THE BATTERY? This must be a common problem. Is there a ground loose somewhere, or a relay that is going out? I have had less problems with my 68 f100.
Thanks guys!
Tony

 

No this is not a common problem. You could have a loose wire someplace or your cables could be starting to go. On an older ford I had I actually burned through the cables from some sort of short. It had a similar problem to yours before going but it was also burning up alternators before we saw the damage to the cables and replaced them.

 

correct me if im wrong......just because they tested the charging system does not mean the altenator is good right? unless you take it off and take it in to them, i didnt know if they could actually test the diode on the altenator with it still being on.

on my 85 diesel, batterys tested good but would drain the battery. i ended up taking off the positive cable on the battery and tested it with a test light by placing the alligator clip of the test light on the positive terminal on the battery, and the test light to the positive battery cable. light lit up, meaning i had a draw coming from somewhere. ended up being a fuse socket that went to the dome lights. even though when i shut the door the dome light would go off. i just pulled the damn fuse cause it was starting to **** me off having dead batterys.

 

I agree, sounds like a) alternator is bad (Just had to replace mine on my 04), b) you have a drain someplace. Even after you turn the key off, there's still something drawing power. But remember, we have keep alive memories, so you'll have to wait 10 minutes or so after shutting off the truck to see if there is still a load.

 

Test the alternator first. There is a lot of parasitic draw testing located in ALLDATAdiy if you end up needing to chase down a gremlin.

 

I have the same prob with my 04 supercrew. Sometimes the truck will be dead overnight. After jump starting the truck it won't go dead for another couple months. But it's going to happen at some point...I just don't know when.

Two years ago I actually could not shut my headlights off. I turned switch to off, clicked the dome light roller to off, pulled the fuse but the headlights stayed on. Had to disconnect the battery anytime I shut the truck off. But the truck stopped doing that on it's own. IDK.

 

I had a problem on a Chev Lumina sedan where the batt would go dead after a night of sitting. Searched all over and tested everything... It came down to a bad switch for the power locks. After pushing the button there were times it was feeding voltage to the lock actuators 24/7.
So there's that possibility...

 

Interesting. I don't look forward to chasing the E-gremlins in these trucks now a days. LOL.

 

Hmmm, my truck had a slow start the other morning. Rolled over real slow, I didn't think it was going to crank. That's the only time it did it. The battery and alternator aren't that old.

 

Had a similar thing happen to my T-Bird. After sitting a few days the battery would be drained. Happened to be working OOT for a few months so had to have a mechanic check it out. Wasn't able to find the issue so he swapped a relay into the main power box under the hood so it wasn't energized till the key was on (meaning you don't have interior lights etc till the key is on). Stopped the problem but wasn't the real fix.

After I got back and had a chance to check things out, found that the little trigger on the glovebox light had broken off and the light was staying on 24/7. Fixed that, problem was gone.

Good luck

 

Using a multimeter, disconnect the positive cable from the battery, and place the meter in series with the battery. With everything off, your shoulndt have more the 25-35 milliamps of draw. If you do, find the fuse panal, and start pulling fuses until the draw drops to this spec. You can also remove the positive cable going to the altenator and see if the draw ill go down.

 

If you have one of those 120VAC inverters, those things have a minimum standby current of up to a couple hundred milliamps unless they're physically switched off. That'll drain your battery.

Stereo amps that are inadvertently wired to be powered on even if your head unit is off will do it too.

If you have a voltmeter, you can check your alt while the engine is running. Anything less than 13.5V or so is suspicious. But the fact that you could drive around after being jumped says it's good

 

Decide on a day to find the energy drain.
Get a clamp on meter. LGT meter;
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Place the meter around the positive cable.
Pull then replace fuses one at a time while checking meter for current drop.
See the owners manual for fuse information (pages 275-282)
https://www.fleet.ford.com/maintenan...ls/default.asp
Wait to pull #5 and #21 as these are keep alive circuits
Of course when you find a drop in current draw on a circuit you need to determine the reason for the drain.

 

truck was dead again. I had driven it for a couple weeks with no problem, then came out and it was dead. I could hear a clicking noise inside the cab. I found the clicking noise in the behind the back seat of the super crew. I pulled the fuse for the power locks, and the clicking stopped. I am going to drive it like that for a days, and if it is fine then i will try to figure out my next step. Does anyone know if there is a relay or someting behind the back seat?

 

It's obviously a drain on the battery. In a case like my cousins where he went through 3 bad NEW batteries, you could unhook both battery cables and if the battery still goes down you know it's the battery.

Sounds like you found the problem though.