I have been living with this same problem on mine for eight years. Too cheap to pay what the dealer wanted to fix it. Years ago they told me the fix was to reprogram the Auxiliary HVAC Control Module and replace all the actuators. $500 just to reprogram the control module plus all the actuators and the labor to do it came to nearly $1000. Needless to say I did not do it.
I unplugged the blend door actuator from the harness and put the blend door to heat and aligned the actuator to match so I could have rear heat in the winter. For the summer I can just plug the actuator back in and it cycles to full cold all on its own.
I hadn't thought about this repair again until just today. I didn't think there was any other way to fix it.
I found a video just a little while ago showing what part needs replaced and what does not.
https://www.youtube.com/watch?v=y4-WlE6-Nkc
I didn't see why the stealership said I had to replace all the actuators when they seemed to work just fine. I was right. Nothing was wrong with mine. The blend door actuator was being told to over travel by the defective control module. Just the usual fleecing of the consumer that they think they have over a barrel.
Also found a great price on the AC Delco 15-73506 equivalent of the second design GM 15832319 Auxiliary HVAC Control Module.
Amazon.com: ACDelco 15-73506 Control Module Kit:...
I found this copy of a GM tech document on another site that explains it all plus a little more.
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#06-01-39-015A: Unable to Control Rear HVAC Temperature or Modes, Intermittent Ticking Noise from Rear HVAC Actuators or Rear HVAC DTCs B0434 or B3764 (Replace Auxiliary HVAC Control Module) - (Jan 12, 2007)
Subject: Unable To Control Rear HVAC Temperature Or Modes, Intermittent Ticking Noise From Rear HVAC Actuators Or Rear HVAC DTCs B0434 Or B3764 (Replace Auxiliary HVAC Control Module)
Models: 2003-2006 Cadillac Escalade Models
2003-2006 Chevrolet Suburban, Tahoe
2003-2006 GMC Yukon Models
with Automatic Control HVAC System and Rear A/C (RPOs CJ2 and C69)
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This bulletin is being revised to correct one of the blower motor control module part numbers. Please discard Corporate Bulletin Number 06-01-39-015 (Section 01 -- HVAC).
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Condition
Some customers may comment on one or more of the following conditions:
• An intermittent ticking/clicking noise from the rear Heating, Ventilation and Air Conditioning (HVAC) system.
• Unable to control rear HVAC system temperature.
• Unable to change rear HVAC system modes.
Technicians may find that Diagnostic Trouble Codes (DTCs) B0434 and/or B3764 have been set.
Cause
These conditions may be caused by HVAC actuators that hunt for the correct position. This cycling may cause a clicking or ticking noise.
An overtravel of the HVAC system control doors may cause one or more of the above system conditions. If an overtravel occurs, a DTC will be set, and the door will go to a preset default position.
When a system door defaults, that door will stay at the default position until the DTC is cleared. Clearing the DTC will allow the door to operate properly until the overtravel condition reoccurs. The following table lists the DTCs that may have been set and the door that is associated with that code.
Overtravel DTC
System Door Affected
B0434
Auxiliary (rear) Air Temperature Actuator
B3764
Auxiliary (rear) Mode Actuator
Correction
Technicians are to replace the auxiliary (rear) HVAC control module with the part number listed in the table below. Refer to the Auxiliary Heater and Air Conditioning Control Module Replacement procedure in SI for more information. This module contains a new calibration to compensate for the actuator overtravel condition and the hunting/clicking noises. The new calibration effectively eliminates DTCs B0434 and B3764. The new control module also eliminates the default position of the doors associated with the DTC. The new control module will allow door travel from counts 0 to 255 without setting a DTC or defaulting the door.
The new auxiliary HVAC control module is compatible with either the first or second design blower motor control module. When using the new auxiliary HVAC control module, the customer may notice a slight increase in the rear blower motor speed (approximately 50 rpm) at a given setting, as compared to the blower motor speed at the same setting with the original HVAC control module. If the customer comments that the increase in blower speed at a given setting is objectionable, the blower motor control module may be replaced with the second design part listed below to correct the slight increase in speed.
The revised auxiliary HVAC control module should not be used unless one or both of the DTCs are set or one or more of the conditions listed above are present. The revised auxiliary HVAC control module will not correct any other DTC or Air Conditioning (A/C) performance concern.
Parts Information
Auxiliary HVAC Control Module Part Number
Description
Qty
15832319
Module Assembly-Auxiliary Heater & A/C Control
1
The blower motor control modules listed below should not be used unless the customer finds the change in blower speeds between the original and the new auxiliary HVAC control modules objectionable.
Blower Motor Control Modules Part Number
Part Description
Vehicle Application
Quantity
89024926
Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)
Escalade, Tahoe, Yukon (vehicles with a short wheelbase)
1
89018849
Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)
Escalade ESV, Suburban, Yukon XL (vehicles with a long wheelbase)
1
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Hope this helps somebody else figure this out as well.