I own a 1993 Dodge W350 and the pcm is no good, and the heat and a/c doesn't work. Is it possible to bypass the pcm via electrical wiring, and if so, how? Thank you in advance!

 

Its not your PCM if the heat doesnt work. You need to do more diagnostics looking specifically at the electrical switches for hvac control and the vacuum system (pump output, sensor on drivers fender, lines from booster into hvac suitcase, and the vacuum servos on top of suitcase.

 

The PCM controls things like:
Charging, cruise control, wait to start /grid heater feature, A/C, ETC.
It does not control the heat.

I got your private message about looking for a PCM, but I would recommend diagnosing the problem a bit more before buying a PCM.

 

Heat and ac ? Is the compressor not coming on, or are you not having the fan motor blowing in the cab ?

The heat is controled by the valve on the heater hoses above the turbocharger. You can manually move that to the other side, and see if you get heat. IF the blower isn't working, check fuses, fusable links, and then you can manually test the motor itself.


Our PCM's as Ollie said, are not doing much of anything other than the few things mentioned.

 

Thank you, I will look into the recommendations mentioned. Here are some of the issues I am having:

• The "wait to start" light stays on constantly
• I've been through a couple of batteries (I replaced the Internal Voltage Regulator with one from Far From Stock)
• I do not believe the cruise control works either
• And the former owner had the A/C wired to a dash toggle to get the compressor working. I would like to fix it where I can control the heat and A/C with the original controls on the dash
• The dome lights don't work
• The "buzzer" sound doesn't come on when you turn the key to the auxiliary position prior to starting