2005 DB9 fan
Author
Discussion

mike-2txrc

Original Poster:

54 posts

5 months

Is th rad fan supposed to run all the time when the engine is running?

Cheers

paulrog1

1,167 posts

162 months

Hi Mike,

If you have the aircon and/or the engine is upto temperature the fans will be on constantly. The fans are controlled by the car PCM and uses pulse width modulation (PWM) to control the speed of both fans.

The sensor in the thermostat housing gives a resistance reading to the PCM.you can get an electrical Multimeter set on resistance and see resistance change when the car is warming up, the resistance from memory goes down as the engine warms up, should around 2500 ohms when the engine is cold and that resistance drops significantly when the engine warms up.