Engine Size: 4.8
Refrigerant Type: R-134a
Ambient Temp: N/A
Pressure Low: N/A
Pressure High: N/A
Country of Origin: United States
Initial problem: truck would randomly blow hot on the driver's side even with control set to full cool. Shutting down vehicle and restarting would correct the problem for a variable length of time.
After researching online, tried disconnecting battery to reset controls and cause a re-calibrate to occur. Re-connected battery and turned key on and didn't touch any of the controls for about 10 minutes. This caused the system to operate properly for about 10 seconds then the mode door would go to full defrost. Great. We've exchanged one problem for another. Unplugged actuator for mode door with system in "face" mode to prevent it from going to defrost mode. (It is HOT here in Houston right now!) System then started blowing hot air on the driver's side after about 5 seconds. Unplugged that actuator in "cold" position.
Question is, is there any way without a fancy-ass GM scan tool to determine if the control head is bad or if it just needs two new actuators? I always try to avoid throwing parts at a repair.
You don't need a GM Tech II scanner - though it is helpful - but you will need a high-end scanner to get the B codes, which will help lead you to the bad actuator. I don't blame you for not wanting to blindly replace parts.
You might be able to pin down the bad actuator by seeing if the resistance on the sensing side of the actuator is feeding back as it cycles. If that portion is open or shorted, you've probably found your problem.
Thanks for the info! I'll probe it with a multimeter and see what I get.
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