In Reply to: Aux Fan Switches/Aux fan resistor posted by ron on February 24, 2000 at 10:59:15:
: 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
I looked in the trusty Bentley manual and learned something myself, thanks for asking the ?
My 535 acts the same way you describe, but like moots was saying my auxiliary fan doesn't come on until the ac is engaged. The manual shows the two high and low relays located in the auxiliary relay box in front of the left shock tower. The one closest to the tower is the high speed relay. The test they give is to check the fan temperature switch located at the top right corner of the radiatior by jumping the Black/grey/yellow with the ignition on; The manual says that if the fan runs only when powered directly, and hot coolant is flowing through the radiator, then the switch is faulty. If the fan won't run when powered directly, then check for power at the relays. They finally tell you to check the resistor mounted on the auxiliary fan housing for an open if the fan operates only on high and no other faults have been found. I hope this helps you, good luck with your search my friend.
'89 535 (needles leanin' to the right at idle)