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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29534
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Why is my heater going from hot to cold only on the

Customer Question

Why is my heater going from hot to cold only on the driverside then i play with the controls and it blows hot again for a few minutes then gies back to cold
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, can I confirm that your drivers side is the one that is malfunctioning, and if so then it sounds like the typical failure of the actuator.

Usually all that is required is the system needs to be re-calibrated 3 times to clean the feedback circuit in the actuator off. This is done by removing the battery for 10 seconds. Attach the battery then start the engine for 3 mins. Shut the engine off and then repeat this 2 more times.

If this does not correct the issue, then we need to replace the actuator. You can use the direction in the document attached.

Thank you for allowing me to assist you. Please rate my answer OK to Excellent service and feel free to ask any follow up questions regarding this issue you may have.
Please know that the only compensation for my time spent assisting you is when you provide that rating.

Customer: replied 1 year ago.
I just chaged the actuator in the summer when it was doing it with the ac blowing cold to hot but now it is reversed
Customer: replied 1 year ago.
Truck has 240000 miles on it could it possably be the controls
Expert:  GM Tech (Cam) replied 1 year ago.

With that many miles it could be the control head. Usually though the actuator is the issue as it has a feedback circuit inside that gets dirty and when it looses its position, it defaults to the full hot. I am not sure what you used for a replacement, but my experience with aftermarket parts on this has not been the most positive. So I guess I am saying that unless you bought GM or AC Delco parts, I would not rule out the actuator. The second thing is to update the firmware in the heater control head (through Dealer programming) in which case it changes the operating characteristics to keep that feedback circuit clean.

Customer: replied 1 year ago.
I did buy ac delco
Customer: replied 1 year ago.
But would that make it go from hot to cold because when i play with the control head it goes back to hot for a few then back to cold
Expert:  GM Tech (Cam) replied 1 year ago.

Yes it would. Knowing you bought the AC Delco, try the recalibration I listed and evaluate it for a couple days then we can see if it needs more.

Customer: replied 1 year ago.
During the calibration does the heater need to be on or off
Expert:  GM Tech (Cam) replied 1 year ago.

On is fine. It does this automatically.

Customer: replied 1 year ago.
I will try it and let you know the outcome
Expert:  GM Tech (Cam) replied 1 year ago.

Thank you.
Please bookmark this page so you can easily navigate back to it so we can continue the discussion. This is done by pressing (CTRL D on PC and CMD D on Mac). You can reply at any time for follow up information regarding this issue, even after you rate the site and I will reply.

Customer: replied 1 year ago.
I wound up changing the actuator again and control head now it is stuck in full hot
Expert:  GM Tech (Cam) replied 1 year ago.

That is very strange. The passengers side operates properly?

Customer: replied 1 year ago.
Yea no problems pasenger side
Expert:  GM Tech (Cam) replied 1 year ago.

And the actuator you are changing is on the bottom of the heater case, very bottom just right of centre?

Customer: replied 1 year ago.
Corecct brand new acdelco does it have to be calibrated
Expert:  GM Tech (Cam) replied 1 year ago.

Yes, take out the HVAC ECAS fuse, wait 10 second, put it back in, start the engine. Wait 5 mins. Repeat for a total of 3 times. Does not matter what setting the heater is on. It will force the recalibration.

Expert:  GM Tech (Cam) replied 1 year ago.

How did that work?