So I was using my 2005 F-150 as a daily commuter until recently when I bought a Maxima. So now the truck sits for 3-7 days at a time without being driven. First week it wasn't driven, the battery was completely dead. I charged it up and it did the same thing the next time. I figured the battery was still stock and needed replacing anyway. So I got a new battery. After 5 days, I checked the battery voltage, and its down to 11.7 volts even on a brand new battery. The difference is the new battery at 11.7 volts still starts no problem, where the old battery would barely start the truck. So I needed to change the battery anyway.

I know a battery does not self discharge itself down to 11.7 volts in 5 days, so I measure the current coming out of the battery and its 2 amps! That's huge. No wonder it's draining the battery so quick. So tonight I started unplugging stuff. I first started with all the mods I've done. Still 2 amps. I pulled the main computer cables off and still 2 amps. I even pulled the 7 pin trailer connector off thinking water might have gotten in there and was causing some leakage. No luck.

Anyone have any suggestions I should try?

 

Ya gotta keep pull'in loads til you find it. It's not disappearing into thin air.

 

With everything off the Radio/Stereo will still draw some power to maintain station memory and the clock.
There are probably more little gremlins like that to draw some power.

 

Make certain you wait until the battery saver times out before looking for parasitic draws.

Normal quiescent draw should be around 50-75 mA.

Also, pull the glovebox and under-hood bulbs to see if the draw goes away.

Steve

 

Ya, I agree. But when you go to a dealership to look at a new truck, you know that some of those trucks haven't been started in weeks. Especially since most dealerships have demo vehicles to test drive. None of those trucks have dead batteries.

 

Thank you. This is one of the things I was looking for. A quiescent of 50-75 mA should last about 55 days on a 100 Ah battery. This sounds about right.

My understanding of the battery saver is that the truck times out after 10 minutes if the dome lights are on. But I'm doing this test with all the doors shut. No lights are on. But I guess I could hook my meter up in such a way that I could walk away for a while to see if it lowers over time.

I ran out of time last night, but I guess the next step is pulling fuses and/or bulbs. I'm more concerned about a hot wire that might have some corrosion to a gnd. It will be hard to find if that is the case. I guess it also can only be something that is hot all the time. Such as:
radio
starter solenoid
maybe the computer

 

look for all aftermarket accessories first... things like CB radios/stereo/ PA systems/ stereo amp that the remote wire doesnt turn off/ small lights....

had this problem before, never did find it... but i tore all my stuff out to sell it, and never did it again...

 

Spike- You can take a test light (sharp probe type) and stick that in the GROUND CLAMP and start pulling fuses and disconnect things. As long as the computers are fired up (no start up draw) and the doors are latched (no dome light or other draw from the dome circuit), you can easily see when the intensity of the test light drops that you have found the culprit. That way you're not having to meter it over and over again. The test light should be quite dim with NO draw and obviously with even anywhere near 1 amp it will be full intensity. I would suggest that if you pull fuses that you pull a fuse and if that doesn't change it, PUT THAT FUSE BACK IN THE CORRECT HOLE THEN! Too many problems caused by getting fuses back in the wrong holes. Also, if you want to work in the truck pulling fuses, just use a phillips screw driver and close the latch so you can work with the doors open and no dome light. Just REMEMBER to pull the handle before you close the door so it releases the latch. Just make sure that any fuses that you pull that have to do with anything that has to fire back up are given the time to do so. I have a couple of digital meters that you remove the fuse and plug it into the side (to give you fuse protection and continuity), and plug the fitting into the fuse holder to check draw on that circuit. They are really handy to put the meter right into circuit to check the draw (in a case just like this when there shouldn't be a draw or not the degree of draw that there is.) By taking things out of circuit and replacing them like this, you should definitely be able to find the problem. Obviously things like selenoid and starter have to isolated in a different way. Good Luck!

 

you MUST wait at least 45 minutes to properly test for draw and the door must stay propped open the whole time to prevent "waking" up the system. Ford workshop book says the system will not have more than 0.5 amp draw after 45 minutes.

I had a similar problem with my 07 and it turned out the fuel pump relay was randomly energizing.

 

Would this workshop info you are talking about be on the Ford DVD's?

I thought the key had to at least be at the accessory position before that relay even got power?

 

Yes this info should be on the DVD. Go to the battery section and following the diagnoses for battery drain.

Exactly hence the reason I had a problem with my fuel pump relay. With my new fuse box my fuel pump only runs with the key in the on position, before it ran until my battery died or I started the truck!

 

Spike easiest thing to do it take it to a dealer you trust and have them diagnose it. I am betting it is the fuse box that needs to be replaced. Also when you have this done get a new battery because my bad fuse box toasted my battery.