Common Causes

When the rear air conditioning in your GMC Yukon isn't working, several issues could be at play:

  • Blown fuse: Check the rear AC blower fuse in the power distribution box under the hood.
  • Faulty blower motor: If no air is coming from the rear vents, the blower motor may have failed.
  • Malfunctioning blower motor resistor: This can cause only certain fan speeds to work or no air flow at all.
  • Clogged expansion valve: This can prevent proper refrigerant flow to the rear AC system.
  • Disconnected or damaged wiring: Look for loose connections or melted plugs, especially at the rear blower motor.
  • Actuator problems: The actuator that controls airflow between hot and cold may be stuck or broken.

Diagnostic Steps

Check the Blower Motor

1. Remove the rear passenger side panel covering the AC unit.

2. Locate the blower motor and check its electrical connections.

3. Test the motor directly with a 12V power source to determine if it's functional.

Inspect the Blower Motor Resistor

1. Find the blower motor resistor, typically located near the blower motor.

2. Check for signs of overheating or damage.

3. Test the resistor with a multimeter to ensure proper functionality.

Examine the Expansion Valve

1. Locate the expansion valve where the AC lines enter the rear of the vehicle.

2. Check for ice buildup, which can indicate a clog.

3. Consider replacing the expansion valve if other components check out.

Verify Actuator Operation

1. Have someone operate the rear climate controls.

2. Listen for the sound of the actuator moving as settings are changed.

3. If no movement is detected, the actuator may need replacement.

Professional Diagnosis

If these steps don't resolve the issue, consider using a scan tool to check for error codes related to the HVAC system. Professional diagnosis may be necessary for more complex issues, especially if refrigerant leaks are suspected.

Preventative Maintenance

To avoid future rear AC problems in your GMC Yukon:

  • Regularly clean or replace cabin air filters
  • Run the AC system periodically, even in cooler months
  • Address any unusual noises or performance issues promptly
  • Schedule annual AC system checks with a qualified technician

By following these steps and maintaining your vehicle's AC system, you can ensure comfortable rides for all passengers in your GMC Yukon, regardless of where they're seated.