Fan 1 Control Circuit Low

Possible causes

• CommonFailed relay
• CommonCorroded relay socket or fuse box connections
• CommonWiring fault between the module and the relay
• CommonWater ingress into the fuse box
• PossibleBlown fuse
• RareFailed control module driver
• CommonFailed or seizing fan motor drawing excessive current

What you might notice

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

What to check, in order

1. Watch the temperature gauge in slow traffic, and stop if it climbs. This fault only bites when the car is stationary, which is exactly when overheating does the most damage.
2. Check whether fan 1 runs at all when the engine is hot or the air conditioning is on.
3. Swap the relay with an identical one from elsewhere in the box and see whether the fault follows it. It costs nothing and is the fastest test available.
4. Inspect the relay socket for corrosion, heat damage and spread terminals - a discoloured socket means the relay has been running hot.
5. Check the fuse for the circuit.
6. Check the fuse box for water ingress, particularly if it is mounted low or in the engine bay.
7. Check the wiring between the module and the relay.