B0429: How to Diagnose & Fix — Auxiliary Air Temperature Actuator Range/Performance
2 vehicles · 2 makes · $60-$500 repair
How to diagnose and fix B0429: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
GMC Yukon · 2007–2014
The small electric blend-door actuators that control temperature and air-flow direction strip their internal plastic gears, producing a repetitive tapping/clicking noise from behind the radio or glovebox and causing the HVAC to blow the wrong temperature (e.g., stuck cold on the passenger side) or fail to change modes. It is one of the most common comfort complaints on the GMT900 Yukon and often affects more than one of the several actuators over the vehicle's life.
Common Symptoms
- Repetitive clicking/tapping behind the dash or glovebox
- One side blows hot while the other blows cold
- Air won't switch between vents/floor/defrost
- Temperature setting doesn't change actual output
How to Fix
Replace the failed actuator with a GM Original Equipment ACDelco unit - the passenger temperature actuator is ACDelco 15-72971 (GM 89018365 / 52402588; aftermarket cross Dorman 604-106). Before buying parts, pull the HVAC fuse for ~60 seconds to force a recalibration in case the fault is only a stuck cal. After replacement, reconnect the battery and let the system self-calibrate. OEM/ACDelco parts are strongly recommended because cheap aftermarket actuators have a high early-failure rate on this platform.
Sources for this issue (1)
Chevrolet Cruze · 2011–2019
The plastic gears inside the HVAC air temperature and mode (defrost) actuators strip, so the door stops reaching its commanded position and the actuator motor hunts back and forth. The signature is a rapid clicking or ticking from behind the dash, usually when the temperature or mode is changed or right after startup, together with air that stays cold on one side while the other side blows hot, or airflow stuck on defrost. Owners often mistake it for a low refrigerant charge or a plugged heater core, but the temperature split between left and right vents points at the blend door.
Common Symptoms
- Rapid clicking or ticking behind the dashboard
- Cold air on one side, hot on the other
- Temperature knob has no effect
- Airflow stuck on defrost or won't change mode
- Clicking that starts on ignition on
How to Fix
Confirm by commanding the actuator through a scan tool's HVAC output test and listening for the clicking, or by pulling the actuator and checking whether its output gear teeth are stripped. Replace the affected actuator (air temperature actuator sits behind the left lower instrument panel on the HVAC case; the mode/defrost actuator is a separate unit) and then run the HVAC calibration/recalibration procedure so the module relearns the door end stops - skipping the relearn makes a good new actuator behave like a failed one.
Sources for this issue (2)
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B0429 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B0429 mean?
B0429 stands for "Auxiliary Air Temperature Actuator Range/Performance." A body code used by General Motors (Chevrolet, GMC, Cadillac) for the auxiliary — typically rear — air temperature blend actuator; some references also render it as rear temperature control circuit out of range. The auxiliary HVAC actuators are 5-wire bi-directional motors with a built-in feedback potentiometer using a low reference, 5-volt reference, position signal, and two control circuits. As the actuator shaft rotates, the position signal varies between 0 and 5 volts, which the module converts to counts (1 volt equals 51 counts, so 0-255); B0429 sets when the reported position falls outside the expected range. The symptom is rear or auxiliary-zone air that will not change temperature, stays stuck hot or cold, or a clicking noise behind the trim. This is a comfort fault, not a drivability or safety issue.
What are the most common causes of B0429?
The most common causes of B0429 are: Failed auxiliary/rear air temperature actuator (stripped gears or a failed feedback potentiometer are common), Actuator harness open or shorted, Poor electrical connection at the actuator — corroded or loose connector, Blend door binding or broken off its pivot, Failed HVAC control module, Actuator not recalibrated after battery disconnect or replacement. The specific cause varies by vehicle.
How much does it cost to fix B0429?
Repair costs for B0429 range from $60 to $500, depending on the vehicle and root cause.
Which vehicles are affected by B0429?
Au7o has documented B0429 across 2 vehicle models from 2 manufacturers: Chevrolet, GMC.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.