B0429 on Chevrolet: How to Diagnose & Fix
Auxiliary Air Temperature Actuator Range/Performance
1 Chevrolet model · 1 documented issue · $120-$450 repair
B0429 on Chevrolet by model: symptoms, diagnosis and fix
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)
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 on a Chevrolet?
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. On Chevrolet it is documented across 1 model: Cruze.
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 on a Chevrolet?
Published repair estimates on Chevrolet range from $120 to $450 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for B0429 on a different make?
View B0429 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.