aux fan

[allerston]

hi guys this has become a consern of mine because i would like to know when does the aux fan come on ,i only seen it coming on one time, and never again is this fan part of the cooling of the engine, or does it come on at a certain temp.can it be reconnected so that it comes on when i start my car and goes of when i switch the car off .what causes this fan to come on
i got a 525 1990 e34 with a m20 engine 12 valve 5 speed manual gearbox:)

[russiankid]

The fan comes on when the temperature in the cooling system exceeds a certain limit. If you live in a relatively cool climate, and your fan clutch is in good working order, you won't see the fan come on unless you have the A/C on.

My AUX fan used to come on when my fan clutch was going out. After replacing the clutch I have only seen the AUX fan come on when I have the A/C on.

[bubba966]

It's turned on and off by the temp sensor in the radiator. #10 here
http://www.realoem.com/bmw/showparts.do?model=HC13&mospid=47402&btnr=17_0099&hg=17&fg=05