Hi guys,

I had the overdrive stop working, as idf you pushed the od off button. We had a quick freeze after warm moist weather, so I'm not sure if that caused it. Has anyone else experienced this?

Grid heater also cut out at same time. No visible ice in the engine bay though.

Anyways, I hope I don't have to buy a new od switch.

 

well just out of a matter of curiosity, are you letting it heat up, or is the engine cold when its not engaging?

 

Unplug the PCM and plug it back in again. Sounds like a PCM problem, hopefully it's just cruddy connections.

It is NOT the OD button. That switch does not actually control the OD, it just tells the computer what you want.

 

I have the "91.5" intercooled diesel. I didn't know it had a pcm. When my voltage regulator went, I assumed that I was pcm free so to speak, as the regulator is on the firewall. I honestly haven't checked into it further since. Where is it located if I have one? I am planning to do a steering cooupler tomorrow, so I can get at things then.

Would this also explain the grid heater going offline? ABS light was on for a couple of days, and then went out as well. I appreciate the help guys.

 

Do yourself a favor and don't even try to fix it. Wire up a switch and mount it on the steering column. All you have to do is ground out the OD solenoid under the dash. It's the best thing I ever did with my truck. As for the heater grid, when mine went it turned out to be a fusible link. To find it gently pull at the edge of each fusible link. They are made of stretchy rubber so if the wire is burned out the link will stretch if the wire is intact it will not.

 

There was a thread here some months ago about the heater fan switch having an effect on the OD function. On mine the OD kicks out/in/out when the heater fan is switched on high. Sometimes it does it on the next to highest speed. The OD switch is powered off the fan switch hot lead. A few others had this same problem too, so see if it goes into OD when you switch off your heater fan.

 

The 91.5 trucks have a PCM that controls the cruise control, grid heaters, OD & possibly a few other things (never checked for sure). The PCM is next to the battery under the fender lip.

 

Okay, mines a '90 so I guess it doesn't apply here.

 

It makes one wornder what the heck DC was thinking when they wired these trucks. I have never seen a vehicle with so many totally retarded wiring ideas. Have they ever heard of a full fuse panel and separate circuits?

 

like the fuse box location & hangers on these trucks??

 

All of my OD problems were corrected by two things... first was installing a speed calibration box as I'm running 35's and the second time I had a problem was when a wire went bad to the CPS.

 

Anyone know if a 93 W250 with auto (A518) will have a PCM?

 

Yep, under the fender next to the battery.

 

Thanks, I will have to check out my PCM!