When should the fan kick in?

[Dad]

Dear forum

Am I correct in assuming that the fan in a series 1 will only kick in once engine water temp has come up to something like 80 degrees? When idling in an ambient temperature of about 20 degrees, approximately how long would you expect this to take? All in centigrade, obviously.

Thanks,

Dominic

[spanish 2+2]

Hi Dominic, yes the fan should come on at 80 degrees and stop when the temperature drops to 72 degrees. Graham.

[kingzetts]

In terms of time to reach 80, it depends. I find if starting from cold it will take as long as 10-15 minutes as there is a large volume of water to heat up, but if coming to a halt and idling after a spirited drive, it will only take perhaps 30 seconds to a minute or so.

[MarekH]

Dear Dominic,

The answer to this question is a little bit more complicated than appears at first blush:-

The Otter switch will turn the fan on and off with some hysteresis as already stated, but because the switch is at the bottom of the radiator, the water may well be 95 or 100 degrees or any other temperature above the thermostat opening temperature when it gets to the top of the radiator.

If the radiator manages to get the water down below the trigger point before the water exits at the bottom, then the fan will not be triggered, no matter how hot it was when it all started.

Thus whether the car is moving, i.e. with airflow, or stuck stationary bumper to bumper in stop-go traffic with the exhaust pipe of the another car infront, will hugely influence the radiator's contribution to the outcome.

kind regards
Marek