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.

 

Your factory gauge should be a volt-meter, NOT an ammeter as on earlier vehicles.


What made the battery low enough to need a jump ??


I understand it is starting fine during all this ??


Two places I would look; one being the fuse-links and the other being the bulk-head connecter.

Either of these can cause funny things to happen with the electrics.



It is also possible that either the regulator or the alternator has gone haywire.

 

The truck has started fine since the jump start. I'm not sure what killed it. It was fine when I drove it around the corner for lunch.

I'm thinking the alternator may be fried and sending weird signals. I'll check the grounds again tomorrow.

 

Test the voltage at the battery with engine OFF; it should be very close to 12.6-volts


Test the voltage at the battery with the engine running and see what you have; it should be something like 14- to 14.5-volts.

Anything higher than about 15-volts means the regulator is not regulating voltage.

 

On the initial dead battery any chance you left the seat warmer on? The bouncing volts needle could indicate your intake heaters cycling.

 

I may have left the seat heater on. I had a bunch of tools in the seat. That may have tripped the sensor.
In my rush to get it wired before they locked down the shop I attached them to a constant hot lead.
I had no problems starting the truck this morning. The intake heater deep cycled and the truck busted right off. The gauge was low like the intake heaters were on for about 20 minutes.
Still, when I hit the power windows or heater I'm rewarded with warning lights.

 

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.

Why would the crank sensor mess with the dash grounds?

 

How would that make the power window switches turn on the warning lights?

 

did you check and clean the ground wires to the rad support? they caused all sorts of funky readings and lights when they came undone for me

 

The ground wire between the battery and radiator support is the one I replaced. I made sure it was getting good contact with bare metal.

 

The problem your are having with the window switch activating the warning lights is because one of your fusible links is blown. I had this very same problem and symptoms and I replaced the fusible link with a self resetting circuit breaker. 30 amp if I remember right. How losing the fusible link back feeds into the warning lights is more than I care to figure out!