Why does my radiator fan only come on when I put my aircon on? sonic

Hi @faiz1 ,

Have you checked that the coolant thermostat is operating?

Try the following:

Ensure that the emergency brake (handbrake) is firmly applied and that the transmission is either in neutral (manual) or park (automatic)

Begin with a cold engine, remove the radiator cap and then start the engine.

Observe the coolant in the neck of the radiator

As the engine warms up, at the pre-determined temperature the thermostat will open allowing coolant to be pumped through the engine..

If you observe the coolant in the neck of the radiator, you will notice that the coolant will change from being still to beginning to "swirl" or "flow" indicating that the thermostat has opened and that the coolant is being pumped through the engine.

As soon as you see this, turn off the engine as the coolant will expand as it gets hotter and will flow out of the neck of the radiator.

If you don’t see this happening either the thermostat is faulty or perhaps the coolant pump may be faulty.

Be careful when you do this as the engine is running