Auxillary Fan switch.

[pyrobee]

could a faulty one of these be causing the Auxillary fan to stay on all the time, and also maybe cause rough idle?

[thebutterson]

They can cause the fan to be stuck on, but I don't see anything they share with idle on the schematic.

The switches power the normal speed and high speed relays, which will allow power to flow to the fan when they are energized. Easiest thing to do would be unplug them and see if your fan stops. If it keeps going with both of them connected it could be a stuck relay, but they don't usually fail like that.

[pyrobee]

where are the normal speed and high speed relays found. the only reason I ask is because the only manual I have at the moment is all in Italian. I need to order a Bentley or find an online one. does anyone know if there are any online manuals for it?

[jeffnhiscars]

where are the normal speed and high speed relays found. the only reason I ask is because the only manual I have at the moment is all in Italian. I need to order a Bentley or find an online one. does anyone know if there are any online manuals for it?

Typically K1 would be the normal speed relay (fuse #3) and K6 is for high speed (I think fuse #18..).

If you jump the resistor for any reason be sure to swap fuse #3 from a 15 to a 30. The wires are the same size so will carry the amperage.

[thebutterson]

http://wedophones.com/BMWManualsLead.htm

You can download a wiring diagram there. It'll show you which fuses and relays are which.

[pyrobee]

What do you mean by jumping the resistor. can you go into a little more detail. I am just guessing I am having a slow day today...

[jeffnhiscars]

What do you mean by jumping the resistor. can you go into a little more detail. I am just guessing I am having a slow day today...

The aux fan is actually a single high speed fan. What gives it a low speed is the resistor thats mounted to the fan housing. Each circuit (high and low) is controlled by one side of the temp switch. The low side is also active whenever your AC compressor is engaged.

The resistors blow and leave that circuit open all the time so if the AC is on the fan will not dissipate heat via the condensor as it should and if the fan wants to run due to a high engine temp, a blown resistor means you dont get that help at low temp..only at high temp.

Jumping the 2 wires that attach to the resistor makes the fan run on high only but since it is fed from the low speed relay via a 15a fuse, it is going to blow when jumped unless you change the fuse to a 30 (which again is safe to do as the wires are .75 for both circuits)