In Reply to: Aux Fan Switches/Aux fan resistor posted by ron on February 24, 2000 at 10:59:15:
The temp on my car shows at mid mark in traffic and a needle's width below during cruise.I have never seen or heard the aux fan running even if I leave the engine running at idle in my driveway for long periods of time.But the radiator fan is clutched and this cooling,I think cools the engine enough that the aux fan doesn,t actually require to run.However the aux fan runs whenever the A/C is switched on.
If you have a look on the RH side of the radiator,there is a temp switch with a three wire plug connected.It is a common ground wire with the other two wires controlling the lo and hi temp
fan speed.try grounding one of the wires at a time and see if there is any difference in the fan speed.
moots '90 520i
: I was just looking thru the latest BMP catalog, and noticed they have replacement (lower temp) aux fan switches that are rated at 82c instead of the factory 91c. Supposedly this allows the aux fan to kick on earlier than the "slightly over midpoint" mark. My aux fan kicks on at midpoint, and i have no cooling problems--i replaced the water pump, thermostat, hoses, etc. but sometimes in traffic the needle still manages to creep a needle width over the mid mark, never any higher. I've just written it off as it might be time to finally replace my radiator, but i'm wondering if one of these $23 switches might be worth a try. Also, if my fan DOES come on, is it likely there's anything wrong with the aux fan resistor? How do you test if you actually have 2 speeds, lo and hi? TIA
: ron 89 525i