1987 Ford Ranger XLT 4cyl gas, manual transmission. I've owned the truck for several months and the battery has gone dead if I let it set for about 48 hours. It had an OLD battery and I assumed that was the problem.

I bought a new battery last week and the problem was worse if anything, so I began testing. The drain with everything off and my stereo unhooked was about .40 milliamps. I spent hours pulling fuses, light bulbs and disconnecting frozen wiring harness connectors with no results.

Eventually, I disconnected the fusible links on the battery side of the solenoid. That reduced the drain to 0. I Isolated the correct link which had two wires: one went to the throttle body and had been up against the manifold at some time and was missing some insulation. I replaced the wire, but still had the drain. The other wire was yellow and I traced it down to the computer wiring harness. This was definitely the problem wire. The truck wouldn't start without it connected. Until I figure out something better or replace the computer, I installed a switch to connect the wire to battery, so I can disconnect it when I park it- like an anti theft switch.

It seem to be running fine that way so far with no more battery drain: .001 milliamps with the memory for my stereo connected. Photo of the offending wire: https://i.imgur.com/YZcbfoC.jpg