You could have a faulty blend actuator that is overtravelling. When this happens it sets a code and will default to hot until the code is cleared. The driver has no way of knowing the code is in the system, unless it is diagnosed with a scan tool. Here is a bulletin that describes what might be going on:
#06-01-38-003: Intermittent Ticking Noise from I/P, Poor A/C Performance, HVAC DTCs B0229, B0414, B0424, B3770, (Reprogram HVAC Control Module) - (Apr 27, 2006)
Subject: Intermittent Ticking Noise from I/P, Poor A/C Performance, HVAC DTCs B0229, B0414, B0424, B3770 (Reprogram HVAC Control Module)
Models: 2004-2006 Cadillac Escalade Models
2004-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2004-2006 GMC Sierra Models, Yukon Models
with Air Conditioning (RPOs CJ2, CJ3)
Some customers may comment on one or more of the following concerns:
" Intermittent ticking/clicking noise from the instrument panel.
" Recirculation mode does not work or Air Conditioning (A/C) system performance is poor during high ambient temperatures.
" Unable to control the driver side temperature.
" Unable to control the passenger side temperature.
" Unable to change the front system modes.
This condition may be caused by the Heating, Ventilation and Air Conditioning (HVAC) actuators that may hunt for the correct commanded 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 concerns listed above. If an overtravel occurs, a Diagnostic Trouble Code (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. After the DTC is cleared, the door will operate properly until the overtravel condition re-occurs.
The following table lists the HVAC system doors and the DTC associated with it.
Air inlet door (recirculation door)
Left temperature door
Right temperature door
Front system mode door
Technicians are to perform the normal diagnostic procedures in SI for these concerns. If diagnostics show that the HVAC system door(s) travel below 5 counts (out of the lower range) or above 250 counts (out of the upper range), then update the software calibrations in the HVAC control module. The new calibrations were made available to dealerships as part of TIS2000 incremental satellite update version 2.5, which was broadcast to dealers in February 2006.
The new calibrations have been updated to compensate for the actuator overtravel condition, the actuator hunting and the ticking/clicking noises. The new calibrations effectively eliminate the codes listed above, the default position of the doors associated with the DTCs and opens up the feedback position value. The new calibrations should not be used unless the vehicle has one or more of the customer concerns listed above or a DTC listed above has been set. The new calibrations will not correct any other DTC or A/C system performance concern.
For vehicles repaired under warranty, use:
HVAC Control Head Module or Assembly Reprogramming with SPS
Use Published Labor Operation Time
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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Wednesday, July 22nd, 2009 AT 9:57 PM