Hey folks, I have a 1990 F150 4x4, 302, automatic, that has a short or something somewhere that is draining the battery. Its a new Interstate battery, no wiring issues that I can see, though I pulled out the fuse for the doorlock a couple years ago when that was quirky. Haven't had the draining issue till more recently, and an alternator test (from a charger) says that it is ok. The problem is that my battery will drain if I leave it hooked up, so I pull off the negative cable when I shut it down. I don't use this truck much, but would like to sell it and would like to fix this problem before I do if I can.
Any ideas about how to start isolating this? I can use a multimeter, but don't have a lot of time

 

If you can measure current draw at the battery, just keep pulling fuses until the draw is gone. Then wring out that curcuit.

 

Thanks, I'll give that try.

 

Depending on how much current, your meter may not be able to handle it.
Use a test lamp in series with the cable.
Use a meduim sized lamp.
It will light telling you enough current is passing to light it up.
There should not be that much.
As soon as you open the major draw, the lamp will go out or very low depending on the lamp size.
I would open the alternator line first to see if the alternator stack or regulator is bad.
If not then proceed to other areas.
Be sure to remove the hood lamp or it will fool you till you find out it is drawing current.

 

Okay, that was my Poor Attempt at a Joke for the day.