Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISHEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHVAC SYSTEM - MANUALDIAGNOSTIC INFORMATION AND PROCEDURESAIR TEMPERATURE MALFUNCTIONCIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Testing
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the air temperature actuator.
- Test for less than 1.0 ohm between the air temperature actuator ground circuit terminal 7 and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify that a test lamp illuminates between the air temperature actuator ignition circuit terminal 10 and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the air temperature actuator.
- Install a DMM between the control circuit terminal 8 and ground. Command the actuator in each direction. Voltage on the control circuit should change from 0 volts when commanding the actuator in one direction to 12 volts in the other direction.
- If the voltage does not change as specified, replace the HVAC control module.
- If all circuits test normal, test or replace the air temperature actuator.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.