1. Power Supply:
* Fuse: Check the fuse box (usually under the hood or inside the van) for a blown fuse related to the rear AC blower. Your owner's manual will show you the fuse diagram.
* Relay: Rear AC blowers often use a relay. Locate the relay (again, consult your owner's manual) and try swapping it with a similar relay (same amperage rating) to see if the problem follows the relay.
* Wiring: Inspect the wiring harness leading to the rear blower motor. Look for any loose connections, broken wires, or corrosion. This often requires tracing the wires from the fuse box/relay to the blower motor itself – it can be a tedious task.
2. Blower Motor:
* Motor Failure: The blower motor itself might be faulty. This is a common cause. Accessing the blower motor usually involves removing parts of the interior trim (this is van-specific, so you will need a repair manual or online guides for your exact year/model). You might be able to test the motor with a multimeter (check for continuity and proper voltage), but this often requires more advanced electrical knowledge and skill.
* Motor Resistance: The motor windings could have high resistance, preventing it from spinning.
3. Controls and Switches:
* Rear AC Controls: Make sure the rear AC system is actually turned on and the fan speed is set to something other than "off" or "0". There may be a separate switch or control panel for the rear AC in your G20.
* Switch Failure: The switch itself may be faulty and not sending the appropriate signal to the blower motor.
4. Other Factors:
* Blends Door: It's possible the blend door (which directs air flow) is stuck and not allowing air to reach the rear vents, even if the blower is running.
* Low Refrigerant: While less likely to directly affect blower operation, extremely low refrigerant can sometimes trigger safety shutdowns which might prevent the blower from coming on.
Troubleshooting Steps:
1. Start with the simplest: Check the fuses and the rear AC controls first.
2. Consult your owner's manual: This is crucial for finding fuse box diagrams, relay locations, and other van-specific information.
3. Visual inspection: Look for any obvious signs of damage to wiring or the blower motor itself.
4. Use a multimeter (if comfortable): Testing voltages and continuity can help pinpoint the problem. However, if you're not comfortable working with electricity, it's best to seek professional help.
5. Seek professional help: If you're unable to find the problem, a qualified mechanic specializing in automotive AC systems is your best bet. They have the tools and experience to diagnose and repair the issue efficiently.
Remember safety first! Disconnect the battery's negative terminal before working on any electrical components in your van. If you're unsure about any step, don't hesitate to consult a professional.
