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Discussion Starter #1
I have A/C, but no heat. I get blower speed control and can move between air coming out of dash vents, floor vents or different combinations. Dealer thought it might be the acuator to blend heat and A/C, replaced actuator but still no heat. Checked HVAC head unit and found that head unit not functioning properly. New head is $502.78!*
Has anyone else had issues with the HVAC control unit?
 

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Did you try the calibration procedure? Search the forums for a thread on it if you are unfamiliar with it.
 

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Discussion Starter #3
Recalibration procedure was the first thing I tried. I also had the vacuum fill on the coolant to make sure there was no air trapped in the heater core.
 

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Actuator Recalibration
When replacing an air temperature, mode, recirculation actuator or the HVAC control assembly, the following calibration process needs to be performed:

Important: Do not adjust any controls on the HVAC control assembly during self-calibration. If interrupted, improper HVAC performance will result.

1) Turn ON the ignition with the engine OFF.

2) Turn the Temperature dial all the way to the right.

3) Turn the blower control dial all the way to the right.

4) Turn the mode position dial all the way to the left.

5) Simultaneously press and hold the A/C and Defrost buttons until the LED's start to flash.

6) Once the LED's stop flashing, calibration is complete.

or may need to get a little fancier:


Condition/Concern:
Some customers may complain that the temperature will go to full hot when they turn the temperature control one click off of full cold. The control head is defaulting to Emergency Mode (this provides HOT air to clear the windshield in Defrost mode). This will happen if the feedback voltage for the air temperature actuators are out of range.

Recommendation/Instructions:
Locally obtain a 60 to 68 ohm 1/2 watt resistor, and install it in-line in circuit 1688 pin F of
 

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Discussion Starter #5
Yep, that was the procedure I followed except the LEDs never stopped flashing, that should have been my first clue. I saw the thread on the resistor fix, but that is not the symptom I have. I have no heat.
 

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Verify that you do not have an air bubble in the heater core. See the threads on the hand job or similar.

If you are sure you have no trapped air and the calibration is not completing, I would reboot the car, try the calibration again and if it fails again, look into a replacement HVAC control unit. Source One has them listed for $100 which is generally half the catalog price

2006 09 Genuine Pontiac Solstice Temp Control No AC 15865390 | eBay

2006-09 GENUINE PONTIAC SOLSTICE TEMP CONTROL NO AC 15865390
 

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Discussion Starter #7
Verified that I have no air bubbles in heater core (see earlier post), have not "re-booted" car. Do I disconnect the battery and wait a few minutes?
 

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I have A/C, but no heat. I get blower speed control and can move between air coming out of dash vents, floor vents or different combinations. Dealer thought it might be the acuator to blend heat and A/C, replaced actuator but still no heat. Checked HVAC head unit and found that head unit not functioning properly. New head is $502.78!*
Has anyone else had issues with the HVAC control unit?
Did the dealer confirm it was the head unit (by scanning codes)?

Also, by "head unit" do you mean the control knob circuitry in the dash? If so, Nalley shows new price as $280, and not difficult to replace yourself.

CONTROL. Heater and AIR CONDITIONING (A/C) Control. INSTRUMENT PANEL PART 3 ELECTRICAL. 2008 Pontiac Solstice # 15865389, 15-73573, 1573573
 

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I've not delved into the actuator actuation activity. Is there a way to confirm that the door is moved into position to draw heat? If the actuator can be manually tripped with a signal or voltage (which I'm assuming it can) you should be able to apply the necessary voltage to move it, or detect if the circuit is sending the signal.

If the signal is not being sent, then the panel circuitry would likely be the culprit, right?

And TS is right, if it's that board in the "head unit" it's not that hard to get at. Heck, even a stooge like me was able to get to it to confirm contact on the blower settings when I was having issues.
 

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HVAC Modification

I had my Solstice upgraded to add Cruise Control. This involved reprogramming the BCM. Ever since the Heater Temperature control, is ALL or Nothing. I tried several times to do the recalibration, but it did not fix the problem. So on to plan B, adding the resister. It went flawlessly, and solved the problem as advertised. I took pictures to document the process, but I don't have sufficient privileges to upload them. If anyone would like them drop me an email. [email protected], and I will be glad to send them, or if someone that has a higher privileges that could post them, maybe they will help someone.:)
 

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HVAC Modification

I had my Solstice upgraded to add Cruise Control. This involved reprogramming the BCM. Ever since the Heater Temperature control, is ALL or Nothing. I tried several times to do the recalibration, but it did not fix the problem. So on to plan B, adding the resister. It went flawlessly, and solved the problem as advertised. I took pictures to document the process, but I don't have sufficient privileges to upload them. If anyone would like them drop me an email. [email protected], and I will be glad to send them, or if someone that has a higher privileges that could post them, maybe they will help someone.:)
Mike could u send me the pics of the register install? Much appreciated. [email protected]
 
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