HVAC Temp dial not working

Tiny
AZNEVILLE
  • 2007 HUMMER H3
  • 5 CYL
  • 4WD
  • AUTOMATIC
  • 87,000 MILES

I have a 2007 Hummer H3, I5. The HVAC temp dial is not working properly. On full cold it works fine. Move it 1 click toward warm it goes full warm. I've replaced the left and right actuators that would affect air temp flow. During HVAC calibration both actuators move. When trying temp dial, only the left actuator moves and it goes the full 90 degrees. I've also replaced the HVAC control unit (entire unit with control dials). What else should I be reviewing?

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Monday, July 4th, 2011 AT 5:43 PM

21 Replies

Tiny
DOCFIXIT
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  • 19,016 POSTS

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

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Monday, July 4th, 2011 AT 7:05 PM
Tiny
AZNEVILLE
  • MEMBER

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.

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Monday, July 4th, 2011 AT 8:08 PM
Tiny
DOCFIXIT
  • EXPERT
  • 19,016 POSTS

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.

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Tuesday, July 5th, 2011 AT 2:59 PM
Tiny
AZNEVILLE
  • MEMBER

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.

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Sunday, July 10th, 2011 AT 7:08 PM
Tiny
ZIGGYMON
  • MEMBER

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

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Tuesday, November 29th, 2011 AT 3:37 PM
Tiny
AZNEVILLE
  • MEMBER

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.

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Tuesday, November 29th, 2011 AT 5:55 PM
Tiny
ZIGGYMON
  • MEMBER

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.

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Tuesday, November 29th, 2011 AT 6:01 PM
Tiny
FACTORYJACK
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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

This PI was superseded to update the Recommendation/Instructions. Please discard PIT4704.

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.

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Wednesday, November 30th, 2011 AT 5:28 AM
Tiny
AZNEVILLE
  • MEMBER

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.

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Wednesday, November 30th, 2011 AT 2:41 PM
Tiny
ZIGGYMON
  • MEMBER

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!

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Wednesday, November 30th, 2011 AT 9:32 PM
Tiny
RIVERMIKERAT
  • MEMBER

Were you able to come to a resolution on this?

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Monday, January 23rd, 2012 AT 7:24 AM
Tiny
AZNEVILLE
  • MEMBER

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.

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Monday, January 23rd, 2012 AT 2:24 PM
Tiny
RIVERMIKERAT
  • MEMBER

Let us know if it doesn't stay fixed.

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Monday, January 23rd, 2012 AT 7:24 PM
Tiny
AZNEVILLE
  • MEMBER

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.

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Tuesday, January 24th, 2012 AT 12:33 AM
Tiny
RIVERMIKERAT
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What about the A/C functions? Do they all work properly?

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Tuesday, January 24th, 2012 AT 12:44 AM
Tiny
AZNEVILLE
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Other functions work properly. Temperature blending is the only issue.

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Tuesday, January 24th, 2012 AT 12:52 AM
Tiny
RIVERMIKERAT
  • MEMBER

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.

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Tuesday, January 24th, 2012 AT 4:23 AM
Tiny
AZNEVILLE
  • MEMBER

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.)

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Tuesday, January 24th, 2012 AT 4:33 AM
Tiny
RIVERMIKERAT
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(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.

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Tuesday, January 24th, 2012 AT 4:47 AM
Tiny
AZNEVILLE
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Will do, though it will be a couple of weeks before I can work on it.

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Tuesday, January 24th, 2012 AT 5:04 AM

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