* Front Blower Motor: The most likely culprit is a faulty front blower motor. It could be burned out, seized, or have a bad connection.
* Front Blower Motor Resistor: The resistor pack controls the fan speeds. A failed resistor will often result in no fan operation at all, or only at the highest speed (if at all).
* Blower Motor Relay: The relay switches power to the blower motor. A failed relay will prevent the motor from receiving power.
* Fuse: Check the fuse(s) related to the front blower motor. A blown fuse will cut power completely.
* Wiring: A break or short in the wiring harness leading to the front blower motor could interrupt the power supply. This is harder to diagnose visually and often requires tracing the wires.
* HVAC Control Module (or Blend Door Actuator): While less likely, a problem with the control module (the computer that manages airflow) or a faulty blend door actuator (which directs air to different vents) could prevent air from reaching the front vents, even if the blower itself is working. This would usually manifest in other symptoms, too.
* Vacuum Leaks (for some climate control systems): Some older systems use vacuum to control air flow. A leak in the vacuum lines could prevent proper air distribution.
Troubleshooting Steps:
1. Check the fuses: Locate the fuse box(es) and check the fuses related to the HVAC system and blower motor.
2. Check the blower motor resistor (if applicable): This is often located behind the glovebox or under the dash. Inspect it for signs of burning or damage.
3. Listen for the blower motor: Turn the fan on. If you hear a clicking sound, the relay or motor may be faulty. If there's no sound at all, check the fuses and wiring.
4. Test the blower motor directly (advanced): This requires disconnecting the motor and testing it with a direct power supply (requires electrical knowledge and caution). Only attempt if comfortable with electrical work.
5. Check the wiring: Visually inspect the wiring harness leading to the blower motor for any damage.
6. Consult a wiring diagram: A wiring diagram for your specific vehicle will show you the path of the wiring and components involved.
Since the rear blower works, it suggests the problem is isolated to the front system components. Start with the simpler checks (fuses, resistor) and progress to more involved diagnostics if necessary. If you're not comfortable working on automotive electrical systems, taking it to a qualified mechanic is recommended.
