HVAC Temp dial not working

Since you did the actuators have you tried to recalibrate it?

1.Ignition on engine off
2.Turn TEMP dial all way to right
3.Turn blower control all way to right
4.Turn mode selector all way to left
5.Simultaneously press and hold the A/C and defrost buttons until LED flashes. LED stops calibration complete

Let me know what happens

Yes, that is the calibration that I performed. I've had the same symptoms with actuators swapped between left and right, new actuators used and a new control unit in place. Both actuators work in calibration mode but not in regular use.

Have you tried having it scanned? Let me do some research you have replaced most possible components.

Scan could help Control head is the fix problem is none about and head does the fix. Have found one case where mode actuator was the fault.

Had it scanned - P0014 was the only stored code and that would likely be unrelated.

New symptom: last week the battery died. After I got it restarted the temp dial would only stay on cold unless moved all of the way to hot. Once moved all of the way to hot, the right actuator would move down incrementally to cold. Once it hit all the way cold, it would not move back up unless the dial was moved to full hot. During this time the left actuator did not move all at, unlike before. After a few tests back and forth the right actuator stopped moving at all.

I performed the HVAC calibration again and the original symptoms reappeared where only the left actuator was moving, and it would move the entire range to full hot when moving one click off cold.

I have the EXACT same problem in my 2007 H3. Did you ever find the problem and solution?

I would really appreciate any kind of help you can provide on this issue. I've tried everything like you and am pulling my hair out trying to find the cause.

Ziggy

No, didn't get it fully fixed. Have replaced both actuators and the control unit. Dealer claimed it was actuators and replaced them (after I replaced the control unit) and it works better, but not properly and not consistently. Moving it one click off of full cold still produces nearly full heat though that's better than before when it went all of the way to full heat. It did work well for about a week or two.

Thanks for the update! I wonder if it could be the connectors not making full contact. I have read where this was a problem with these vehicles.

Since the system is manual, there is very little scan information that would apply. A/C request and A/C pressure sensor data is it. There are a couple bulletins, one of which matches the concern of goes full hot when one click off cold, I will include that in the following. It references replacing the control unit with a specific part number, was that the number that you used? It also states that the control head defaults when feedback voltage is out of range, although no specification on what the range is. Looking at the schematic and reading the description, I would suspect outside being the extreme of either 0 or 5 volts.

#PIT4704A: HVAC Temperature Goes Full Hot When One Click Off Full Cold - keywords A/C AC actuator air compressor door heat heater mode - (Feb 18, 2010)







Subject:

HVAC Temperature Goes Full Hot When One Click Off Full Cold






Models:

2006-2008 Hummer H3



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This PI was superseded to update the Recommendation/Instructions. Please discard PIT4704.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

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 for safety reasons which would be available 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:


Replace the HVAC control head with part number 25920831.

I replaced it with a part from a 2009 truck. I will look into purchasing a whole new unit though I suspect there could be voltage issues as well. How to track down the cause of those issues? I don't know.

Thanks gstacey for your detailed information. I tried to find TSB #PIT4704A, but had no luck. Found the newer part though. Most of the successful posts I read indicated replacing the HVAC control module. I too tried a used module with no luck. Maybe all the older versions go out!!!

Were you able to come to a resolution on this?

Sort of. Everything is working now after both blend doors and the HVAC control panel were replaced. The air flow worked properly for a month, then reverted to the all hot/all cold problem, then another month later it fixed itself and has been working properly since.

Let us know if it doesn't stay fixed.

Ironically it failed again today - actually it was probably Saturday but just noticed it today.

Battery died on Saturday when doing work to the rear end as the ignition was left on (truck was not running) while the shifter was in Neutral. Battery was put on a charger and recharged in a couple of hours (battery is about three months old).

I did the HVAC reset and I could hear it running its processes of opening/closing doors, changing fans speeds, etc. but it didn't fix the issue.

Not sure if it is "normal" but when moving one or more clicks off of full cold it takes about 5-10 seconds before the blend doors move.

What about the A/C functions? Do they all work properly?

Other functions work properly. Temperature blending is the only issue.

Damn. I was afraid you were going to say that. I just spent an hour reviewing our reference material to see if there was some diagnostic steps I could give you and your problem doesn't come anywhere near any of those listed.

I wonder if somehow it is tied to any other DIC or error messages, or other safety system. While working on the truck someone depressed the brake pedal. Since the pads were out of one caliper the caliper was hyperextended giving me Traction Failed, Serv Stab Sys and Brakes Fluid errors. Brakes were bled, fluid topped off, everything is working but errors haven't cleared yet. The only two triggers for this issue were the battery and the new DIC messages.

Once the messages clear in a few days I'm hoping the HVAC will clear up. They shouldn't be tied together but who knows - it doesn't make sense the way it is now, so maybe a strange solution will be the right one. (Grasping at straws here.)

(Handing another straw) Take it to a shop to have the codes cleared manually.

Try this: Check the voltage to the fan control switch and the actuators (if applicable). If applicable, measure vacuum anywhere you can reach it. Write down what you measure and where and let us know what you find.

Will do, though it will be a couple of weeks before I can work on it.

Ok.

I read posts concerning inop HVAC control.

After replacing a dead battery, the HVAC would blow full hot 2 clicks off of cold.tried recalibration several times with no luck, then i saw mention of feedback voltage being
out of spec. The new battery was 100% top charged but during the cal procedure the fan is on high.

I hooked up a high amp charger to boost system voltage -- problem solved!!!

2009 H3

I know this thread is really old but I was wondering if anyone had found a resolution to the issue? I just purchased a 2007 H3 with 35,000 miles. Looks new and still smells new. I am having the exact same issue as described; one click off max cold and I’m getting full heat. I have a code reader and there are no unknown codes (radio com code due to aftermarket stereo). Any help is appreciated.

Has anyone tried replacing the voltage regulator or alternator to get higher voltage? Having same issues with my 2007.

Hello, I'm Danny.

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