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Climate Control fix

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
This should fix the problem of turning the far left climate control knob off of max cold temp and have it blow hot air with no variable.
I did some searching and someone else discovered this fix, not sure who originated it.
This supposedly would get the reference voltage (5 volts?) regulated again if the switch circuitry has failed or wherever the 5 volts originates.

  • The light blue with black stripe wire, terminal f circuit 1688, on the driver side of the hvac control head needs 68 ohm 1/2 watt resistor installed inline.

The procedure here is the HUNNER method of installing it. Proceed at your own risk.

  • I did not disconnect the battery as I wanted to confirm this resistor fixed it instead of by some fluke disconnecting the battery did.
  • Set the parking brake. Turn the key on.
  • It helps to shift to Low. However leaving the key on will drive you nuts so after removing the dash piece I put it back in park.
  • Disconnecting the battery would of course shut the dinger bell off. So I would recommend that and you can leave it in low to have more room, now that we know this did fix it. (fingers crossed)
  • First you have to do the stick your fingers in the DC sockets and pull up and out.
  • I cut me a piece of cardboard for a work surface in case solder dropped.
  • I disconnected the plug from the back of the switch to get more room to work
  • Find the light blue wire with black stripe. I peeled back the high quality gooey sticky black electrical tape GM chose to use far enough to expose the wire back into the loom so I could slide on some shrink wrap long enough to cover the splice.
  • Call me old school, I'm old and went to school, but just as in my battery thread I make a physical connection first then solder.
  • I used some forceps for a heat sink.
  • I used a Radio Shack 68 ohm 1/2 watt resistor. They come 5 to a pack for $1.30 or $.26 a piece.
  • If you don't know, use a low wattage iron so as not to fry the insulation on each end. Heat the wire until it pulls some solder as you feed it.
  • Use some fine solder, Radio Shack still has that!
  • Grabbed a short piece of shrink wrap I keep around. After the solder area cools slide the shrink wrap you remembered to slide on BEFORE you soldered over the entire splice. Use a heat gun carefully to shrink the wrap and secure and insulate your splice. I did not re-tape it at this time as I wanted to test it first. I will use a high grade of black electrical tape or some loom.
Now in transitional fall weather you can adjust the air temp but leave on the air conditioning to freshen your cabin temp and humidity!
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Here was a tech sheet on the problem.
#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 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.
----------------------------------------------------------------------------------------------------------------

The alternative from GMpartswarehouse (hope this link works it was a copy of the cart) may go away but it is $264.13 shipped.
Not sure this would fix it if Alrock had no success?

http://store.gmpartshouse.com/shopp...&subgroup=&component=&startrow=51&searchtext=
 
Last edited:

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
YES! so far so good. I have been about 30 miles running around gathering up other things and have messed with it repeatedly and so far so good.
 

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
Just be careful and don't burn thru.
A heat gun is a good investment for all kinds of other things.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
•Turn ON the ignition with the engine OFF.
•Turn the Temperature dial all the way to the right.
•Turn the blower control dial all the way to the right.
•Turn the mode position dial all the way to the left.
•Simultaneously press and hold the A/C and Defrost buttons until the LEDs start to flash
•Once the LEDs stop flashing, calibration is complete.

Or . . . disconnect the negative battery terminal, reconnect, start the truck. That should also start the calibration cycle (it did when I swapped batteries a couple of nights ago).
 

tsanchan202

Member
Messages
17
Location
Arad, Israel
Thank you so much for this fix! I had this problem recently with my 2007 H3 and since I am in Israel, the dealer cost to order and install the HVAC control head was over $1000.00 !! I performed this fix for about $0.28. Thanks again from the Holy Land!!!
IMG_5102.jpg
 

Steve #1

Well-Known Member
Messages
534
Location
TEXAS
So I tried the 68 ohm 1/2 watt resistor and it's still not working for me. I didn't check the voltage before or after installing the resistor so not sure what the voltage is. Hunner, I'm curious, before I go pulling things apart, if you were able to determine if this is a problem with the controller reading the reference voltage or if the reference voltage that it is receiving is out of range?
 

Best4x4

Well-Known Member
Messages
1,042
Location
Vidor, TX
So I was driving my wife's 07 H3 on Sunday and when I went to lower the HVAC just two clicks made it basically go full heat. I could still hear the compressor cycle, but it was only blowing hot air. Put it back two clicks and boom cold air again. Hunner is your mod still working good for you? I guess it won't hurt to try the mod. If it doesn't work I can always remove it. If it doesn't work should I start inspecting blend motors? I recently changed the battery so I know I calibrated it not to long ago.

I had a Pontiac HVAC unit in it for a while until I realized it's programmed differently and functions slightly different (recirculate is actually working when the LED is off, and apparently it was setup for a convertible because if u ran the AC long enough it starts to freeze over). Slapped the OEM unit in and those issues went away, but now since it's getting cooler I noticed the two click business when trying to raise the cabin temp slightly vs max heat at two clicks lol.
 

derian06

Red Rockett
Messages
1,866
Location
Madison, AL
So I was driving my wife's 07 H3 on Sunday and when I went to lower the HVAC just two clicks made it basically go full heat. I could still hear the compressor cycle, but it was only blowing hot air. Put it back two clicks and boom cold air again. Hunner is your mod still working good for you? I guess it won't hurt to try the mod. If it doesn't work I can always remove it. If it doesn't work should I start inspecting blend motors? I recently changed the battery so I know I calibrated it not to long ago.

I had a Pontiac HVAC unit in it for a while until I realized it's programmed differently and functions slightly different (recirculate is actually working when the LED is off, and apparently it was setup for a convertible because if u ran the AC long enough it starts to freeze over). Slapped the OEM unit in and those issues went away, but now since it's getting cooler I noticed the two click business when trying to raise the cabin temp slightly vs max heat at two clicks lol.

Theres a way to reset it so it goes back to normal, but i forgot how.
 

Best4x4

Well-Known Member
Messages
1,042
Location
Vidor, TX
Did the mod after tracking down a resistor. Did a test run, it worked so I just cleaned up the wiring so it looks 100% OEM and I'm good to go. GM probably did this at the dealership vs actually replace HVAC panels.
 

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
Yes mine is still working thankfully in the strange range of temperatures we are having in Arkansas now.
It's Fall You'all!
 

Best4x4

Well-Known Member
Messages
1,042
Location
Vidor, TX
Yeah it's working great on my 07 now. It's fall, but here in TX it's in the 50's to upper 80's so far. Can't wait for cooler weather!!! Just glad it was a quick simple fix vs tearing into it like a Jeep WJ or Land Rover Range Rover. Their electronic blend HVAC systems are fun to work on if they act up!
 

VIPNiSS

Member
Messages
21
Location
Atlanta
Thank you for this thread. I went to radio shack today and spent $21. $1.49 for 5 resistors, soldering gun kit $14.99 and heat shrink pack $6.99. Did exactly this and it was fixed!
 
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