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.

Those seat heaters suck up a bunch of juice maybe that's the problem.

Those heaters draw 70 watts. They have 10 amp fuses. The radio pulls more current.

The heaters are not connected to the factory harness. The truck was fine on the drive in and fine when I went to lunch. It was not fine after work.
Since I was more concerned with the poor road conditions than the running state of the truck I may have overlooked a charging issue earlier.

I'm thinking it's a ground or alternator problem. There's no reason for the heaters to make the brake warning light come on when I hit the window switch.
I did roll down the window that morning so the problem started after lunch.

Sounds like a connection problem, ground etc. to me.

It sounds like a ground problem. You wouldn't believe some problems you see when installing stereos that they had other places do.

I'll have to chase the grounds for the cluster and dash. I didn't mess with any of that when installing the seat heaters.
I wonder if the grounds got ugly inside the truck while the battery ground was loose. Maybe a small ground was trying to carry too large of a load.

Should have just gone ahead and fixed the heater core. All the steam probably fired your electrics.

I dunno the specifics of your truck, but I do know that on my 89 turbo voyager the wiring for the computer passed near to teh battery and all it would take is one good acid spill or boil over and the wiring would corrode showing all sorts of weird symptoms.

I would start with a good charge and load test on your battery. It might be flaking out on you , I've seen that cause funky symptoms too.

The dashectomy required to do the heater core is what stopepd me from replacing the core. I've been busy with other things and haven't been able to dedicate a full weekend to do it.

It can't be that big a job. I pulled the complete a/c system inside and out off my 74 in one day including redoing the heater box to work with no a/c. It isn't as hard as it looks once you get started.

On these newer trucks, you need to pull the dash out to get to the core. Its a pain in the butt. I liked my 91 Bronco. Open the glove box, take out the liner and there were the bolts. 2 hose clamps and its out. 30 minutes start to stop. Sorry, not trying to rub it in.

That looks like about 4 or 5 hrs work at most. Okay for you maybe 6 or 8. But It's still a one day job.

I haven't had the time.

BUT

That won't fix the current problem.

I replaced the battery to chassis ground. That didn't fix it.
I'm getting 12.5 volts at the battery with the engine off and 14.5 volts with it running. I checked for a/c current with the engine running and got .4 volts. That rules out a bad diode in the alternator.

The problem is still there. The only wires we disturbed run to the brake controller and manual OD switch.
A quick look didn't turn up any bad fusible links or bulkhead problems.

I had somewhat similar symptoms on a Neon. Long story short it was a ground wire. I know you checked the main ground but it may be one of the others.

It sure sounds like a ground. I need to find a dash ground. The window switches turning on the warning lights is just bizarre.

I've got a factory service manual for the truck. I need to break it out and find the common connections between those circuits.

The electrical components will do what it can to find a ground. Even feed back through other items. You ever see the car that turns on its blinker on to see the lights alternate from left to right, but 1 is brighter? Usually thats a bad ground in the socket and its using the ground from the other side. Did you do a voltage drop from the battery to the ground? Put the lead on the positive and then move from the battery post to the cable, to the other end of the ground cable to the bolt to the frame. All the while leave the red lead on the positive. Also, try removing fuses of hte affected circuits and see if the problem persists. This may help narrow down the circuit.

It actually sounds like a problem in the fuse box. make sure with the rotten weather you have had that you don't have a fuse box with moisture in it or rust between the contacts. Ran into a back feed the other day that was caused by poor ground connection and a faulty fuse holder in box. Caused lights to go on and other to go out by the way it would cure itself as soon as temp came up over 40 degree's Too cold to work on outside so hang tight

check for bad batt. just yesterday wifes o4 pacifica won't start.no crank.jump started and noticed dash and int lights dimming and getting bright.put voltmeter across bat and voltage jumping 1 1/2 volts.shut off and connected jumper cables.still jumping.replaced bat and started all normal.

On Jeeps, they run a lot of wires into the door on the drivers side, and over time, those wires break. Might be a place to check, although the only thing you have said that might point there is using the window, and getting warning lights in the dash. It might be a similar problem with Dodges.

How about adding a couple new grounds to rule out the existing ones? I'd run a new one from the block or head to the firewall, and one from the firewall to the dash and/or steering column. I'd also clean the contact points for any electrical component that mounts to any sheet metal in the engine compartment to insure they also have good grounds. Can't have too many grounds...

Digging through the factory diagrams it looks like all in-cab electrical stuff grounds through the body of the healight switch.

I fiddled around with it this weekend. The fuse box has three buss bars in it. One of them runs the door locks and A/C. Both are high amperage consumers. There was enough voltage at the bus to turn on a trouble light.
I pulled the fuse (circuit breaker actually) for the windows and jumped power from another bus bar to the output side of the fuse. The windows worked fine and did not turn on the trouble lights.
This tells me that it's an amperage supply issue and not a ground.
I will have to go through the power supply and bulkhead connector to look for issues. I'm strongly considering replacing the fusible links with fuses.

I guess I'll go through everything while the dash is out. Put the blower motor on a relay, replace the fusible links with fuses, and improve the dash lighting.

Think before replacing the fusible links with fuses because the fuses won't be able to deal with the spikes that links will. The starting draw on some of the acessoties is higher than the fuse ratings.

Looking at the gauge of wires they used a 30 amp fuse should work. If it presents an issue I can switch to drop in 30 amp circuit breakers.

There are three fusible links going into the fuse block. I planned on replacing each of them with a fused lead. If I put the blower motor on a relay for high speed it will take a big load off the fuse block. They are known to melt fuses and fuse blocks. My headlamps are already on relays.

i agree probable ground problem...pull off the ground at the body and sand it or grind it clean...TIGHTENING A GROUND ISNT GOOD ENOUGH! also test the alternator..maybe a diode is leaking back.. do this before you go any further on the high voltage relays etc.. dan

I've gone through the grounds, alternator, and battery.

It's got to be the power source. A bad ground wouldn't suddenly get better when you supply a new power source.