I managed to kill the battery on my 92 D250 today. I jump started the truck (properly, no crossed wires) using a coworkers 07 CTD. After it started the alternator gauge showed discharge. Fearing a dead alternator, I left the truck running while I did a little work. 15 minutes later, the charge needle was bouncing back and forth somewhat rapidly. I shut the truck off and the battery was able to fire it up again with no issues. I restarted it again a few minutes later and the charge needle was a little on the high side as to be expected.

The weird thing is when I turn on the heater/vent/ac or try to operate the power windows the warning lights for the brakes, water in fuel, and wait to start indicators light up. The windows do not work and the heater fan is stuck on low speed. All other electrical systems work normally.

I drove the truck around for 45 minutes and nothing changed. I parked it and it had the same behavior on the restart a few hours later.

On the way home tonight, the charge needle was very low light the intake heater was on. 10 minutes later it was bouncing around rapidly and finally settled down a little on the high side.

Any ideas what the problem might be? I did tighten a loose ground from the battery to the radiator support about half way through this mess. The battery cables are tight and clean.

It did drop down to 17 degrees tonight. That's the coldest temp we've had around here in several years.

This should have nothing to do with my seat heaters. They are drawn from the battery and ground to the chassis. I did not touch the factory wire harness on the installation.