Hi everybody,
Im new to the forum and i have a problem that I cannot figure out for the life of me.
Ive got an 86 f150 4x4 w the 5.0 For the last few months my battery has been draining overnite, Ive replaced the statrer, alternator, battery and Ive checked all the ways I know how to find a short somewhere, Ive taken all unnecasary fuses out ie: stereo,dash lights etc. and left truck overnite and still having the same problem.
At first when I changed the alternator and starter the problem was gone a few days than came back.
Most of the time I can park the truck for 8 hours at work and it will start when I get off, and then other days it wont. The only option i can think of now is to install a battery cut-off switch but thats the last resort, becasue it will reset all my stereo settings ever night.
Any info you can give me wouLD be greaT
THANKS ALOTT!!

 

My guess would be a relay stuck closed some were that is pulling power off your battery for something.All the newer vels have relays for something and fuses for protection.PS How is your ign is it working ok?a bad switch may not cut off all the way at times.I wish had more places to to check out for you,keep us posted on what you find.

 

If you disconnect the battery alltogether, does it still die? Try that first and see what happens. If it still dies with the battery cable disconnected, it's the battery, not the truck.

-Joe

 

I disconnect the battery at night and it holds the charge, and as for my ignition I believe its working fine it doesnt stick or anything

 

You are missing the fault by guessing and spending all the money.
Measure the current drain with a meter or the right size lamp in series with the positive cable.
Using a lamp as a test device needs a lamp that won't light on less than 1 amp current so you can see it go out once the drain has been interrupted.
With a monitor of some sort, you can seperate/isolate the circuit that is causing the problem.
An overnite drain on a fully charged good battery is roughly a 15 to 20 amp drain, so figure your current meter or monitor lamp size for that level to start with.
With EFI, there is a certain min drain at all times that consist of the computer memory and any other devices that have memory to be maintained. This drain is usually well less than 1/2 amp and would run the battery down over a long time interval for the same reasons, usually in 3 months or more.
You can find it if you look using a better way.
Good luck.

 

I don't know if this will work for you as it did for me since I have OBD2

Remove the ground cable. Using a test light and a set of gator clamps, connect the test light ground to the cable. Connect one end of the gator clamp lead to the ground cable. Connect the other end of the gator clamp to the metal part of the test light. Hold it on the negative terminal of the battery for at least one minute. after one minute, remove just the gator clamp from the test light metal. If the light doesn't go out in about 5 or 6 seconds, theres a drain. Start by pulling fuses one at a time and testing until the light goes out. Then you have your drain

 

Is the truck EFI? If so, try pulling the fuel pump relay, or tripping the inertia switch (whichever one is easier to get to). You should have the one with the white button on the firewall beside the trans hump in the passenger footwell. Just lift the button (on either style) to trip the switch off.

 

Where is the interia switch?...or relay?

 

there are probably something like a hundred relays in your truck

 

Read my last post. Then read this thread.
You're thinking of YOURS. On an '87, there are less than a dozen, even with EVERY factory option.

 

Ill take your word for it, but i just assumed there were still alot of electrical power items, window motors, wiper motors, headlights, tail lights etc. Idk im sure i exagerated a little just to point out that there isnt "one relay"

 

I had a problem like this. My radio went bad, and was draining the battery 24/7. As soon as I pulled it, the draining stopped.

 

Pat
Of the things you listed, NONE uses a relay on an '87 F150, unless he has interval wipers, in which case there's a relay (that can't be seen or serviced) inside the interval governor. Sort of like the LCM on your truck - there are relays in it for the headlights & taillights, but those can't be seen or serviced. Ford has never used relays for power windows, other than for the auto-down (or -up) function.

 

Thanks everyoine fer ur help, tommorow I will try flipping the interia switch and see if she drains, Ill keep ya posted