How much current should run thru the #12 IOD fuse with the key in the off position? I can not keep my batteries charged, and finally got around to checking it out. I connected only one battery to the positive cable, then put my multimeter between the negative battery post and the negative cable. I found a draw of 2.35 amps. I pulled all the fuses one by one, and the only one that had a significant impact was the IOD fuse, a few others dropped 0.01 amps or so.

 

That's way too much, I don't know the exact number, but it should only be milliamps. Find a wiring diagram, look for the loads on that circuit. Disconnect one at a time until you see the amps drop. HTH

 

Disconnect your cell phone charger or whatever is in the cigar lighter hole. just a thought.

 

Couple other things to check......It is common on these trucks for the switches on the glove box and underhood lights to fail, leaving the light on continuously. Doesn't take long to discharge the batteries that way, especially if they're in marginal condition. HTH