Drain on Battery

Temporary fix - remove your Negative cable at night when you park the truck or any other time depending on how serious it is.

Get a multimeter and put it in the amps scale or use a 12V bulb and a socket with leads on it. Put it in series with the negative lead and the battery. A current drain will light the bulb or show on your meter. Remove one wire at a time from your start relay making note of which one removes the current drain. You are now down to the main circuit causing the problem. Put it back on and go into the fuse box and remove one fuse at a time until the drain stops.

If removing fuses didn't stop it the problem is most likely a rub thru short someplace in the engine compartment, follow the wire and check places where it touches metal. If removing fuses stoppped it, follow that circuit out. Could be a short or an unnoticed curtesy lamp on like the one in the glove box or the one in the back that lights your cargo area.

Also, problems with the voltage regulator/alternator have also caused this type problem, so in your removal of wires from the start relay, include the charge lead from the alternator.

Hope that gets you going in the right direction.

Good luck,