I need assistance diagnosing my HVAC / ATC system. The system has been acting strange for the past few months and today, the ATC stopped responding to input from the panel. I could change temperature from the steering wheel controls, but not from the panel. Once I shut off and restarted the truck, the panel again began responding.

Here is an example of what I mean when I say the system has been acting odd:

• Outside temperature is 37-degrees
• Truck is fully warmed up
• ATC set at 72-degrees
• Cold air is blowing out of dash vents
• Set ATC to 90-degrees
• Cold air continues blowing out of dash vents
• Push button to direct air to the floor vents
• Cold air continues blowing out of dash vents
• Turned HVAC system off/on
• Cold air continues blowing out of dash vents.
• The system did not begin blowing warm air until I set the temperature on the ATC to 60-degrees, and then bumped it back to 72-degrees.

Additionally, in warmer weather with the AC running, the temperature of the air blowing from the vents would randomly become warm and humid. I would have to set the ATC to 90-degrees, then back it back down to get cold air again.

Today, the ATC stopped responding all together.

This seems to me to be an ATC problem. Are ATCs prone to failure? If so, are they easy to swap out in the driveway? I doubt a Chilton’s manual will outline this procedure. Where can I find instructions to replace the ATC?

Any assistance correcting this problem is appreciated.

Thanks,
Jeff

 

There is a service message for erratic operation of temperature control. There is an updated blend door actuator for EATC systems but it will be hard to find right now. They just started coming in off back order this week.

 

Thanks for the info. Would this Service Message cover the EATC locking up like it did a couple of weeks ago? Are the two related?

-Jeff

 

Possibly, but I cant say for sure. I have had to replace some control heads for blanking out completely. But most of your symtoms are pointing to the blend door controller faults of the TSB.