1. Fan Motor: This is the most likely culprit. The blower motor itself might be failing, its resistor pack (controls fan speeds) might be bad, or there might be a problem with the wiring to the motor.
* Test: Turn the fan on to different speeds. If it doesn't work at all, the motor or wiring is likely the problem. If it works on some speeds but not others, the resistor pack is suspect.
* Solution: Replacing the blower motor or resistor pack usually requires some mechanical skills. You might need to access it under the dashboard, which can be tricky.
2. Fuse/Circuit Breaker: A blown fuse or tripped circuit breaker will prevent the fan from working.
* Test: Check your owner's manual for the fuse or circuit breaker location related to the heater fan. Inspect the fuse visually for a broken filament or the circuit breaker for a tripped position.
* Solution: Replace a blown fuse or reset a tripped circuit breaker.
3. Blend Door Actuator: This controls the direction of the air (face, feet, defrost). If it's malfunctioning, it might block airflow completely or direct it somewhere you don't want it.
* Test: Try changing the air direction settings. If the air doesn't change direction at all, or only changes in one direction, the actuator could be the problem.
* Solution: Replacing the blend door actuator usually requires some disassembly of the dashboard.
4. Low Coolant: If your coolant level is low, the heater core won't have enough hot coolant to heat the air.
* Test: Check your coolant level in the overflow reservoir.
* Solution: Add coolant if it's low. If the level keeps dropping, you might have a leak somewhere in the cooling system.
5. Heater Core: The heater core is a small radiator that heats the air. If it's clogged, leaking, or otherwise damaged, it won't heat the air effectively.
* Test: This is difficult to test without some experience. If you suspect this, take your car to a mechanic.
* Solution: Repairing or replacing the heater core is a major job, typically requiring dashboard disassembly.
6. Vacuum Leaks: Some heater controls are vacuum-operated. A leak in the vacuum lines can affect operation.
* Test: This is difficult to diagnose without specialized tools and experience.
* Solution: A mechanic should address vacuum issues.
Recommendation: Start with the simplest checks (fuse/circuit breaker, coolant level). If those are fine, the fan motor or resistor pack are the most likely next culprits. If you're not comfortable working on your car's electrical system, take it to a mechanic for diagnosis and repair. The location and complexity of the parts make this a job best suited to someone with experience.
