Fan Speed Low

Possible causes

• CommonFailed fan motor
• CommonFailed fan relay or control module
• CommonBlown fuse on the fan circuit
• CommonCorroded connector or damaged wiring
• PossibleDebris jamming the fan
• PossibleCorroded earth at the fan
• RareFailed control module driver
• CommonFan motor worn, so it turns slowly
• CommonHigh resistance in the fan supply or earth
• CommonFan speed sensor or feedback circuit fault

What you might notice

• Engine running hot in traffic but cool at speed
• Cooling fan not running, or running constantly
• Air conditioning performance poor at low speed
• Temperature gauge climbing when stationary
• Check engine light on

What to check, in order

1. Perform a voltage drop test on the fan supply and earth. A fan running on reduced voltage turns slowly while testing as electrically connected.
2. Check for debris dragging on the blades.
3. Listen for bearing noise from the motor.
4. Watch the temperature gauge in slow traffic and stop if it climbs. A fan fault shows itself when the car is stationary and clears at speed, because airflow through the radiator does the fan's job - that pattern is the clearest evidence available and costs nothing to observe.
5. Check whether the fan runs at all when the engine is hot or the air conditioning is on.
6. Check the fuse and swap the relay with an identical one from elsewhere in the box.
7. Inspect the connector and the fan earth for corrosion.
8. Check for debris in the fan and that it spins freely with the engine off and cool.