I have one more test to do, but it looks like the OD side of the PCM fried. I called NAPA and they only R&R PCM's. I cannot have the truck down that long. Where can I get a refurbished PCM for a 1992 W350 with the A518?

 

I got one from Advanced Auto, so far so good. Fixed the cold/grid heater issues I was having.

 

i know someone running one from a ramcharger, the only thing that doesnt work automatically is the grid heaters

 

Thanks, I wanted to be able to control my OD with a switch, so I cut the ground wire to the solinoid and ran a line to the cab with the switch installed. Guess What? It still would not shift out of overdrive. In fact I removed the switch and let the ends of the wire hang. We will be going into the tranny as schedule permits to repair or replace the grounded wire to the soliniod or the brand new bad solinoid itself. Whatever the case. Chasing electrical issues in an old truck can cause one to loose their religion . Bottom line, I don't think the PCM is at fault because the solinoid is switched by the computer on the ground wire, not the feed. With the ground wire removed from the circuit the OD should not work, but it does. I most admit I am getting quite an education on drive line componets. I 'm no expert, but I am still trainable.

 

Well it doesn't look like the PCM. I spliced a switch into the power side of the OD solinoid and I can turn OD on/off at a whim. Tim and I will be pulling the pan next week or so and looking for an errant ground under the filter or valve body. Meanwhile I will just play with another toggle switch. Tonight I sleep!