Aux fan/temp switch questions

[BMW BMXER]

My understanding of the temperature switch and there function:
When the underhood temperature of the car reaches a set degree the aux fan kicks on to keep the car cool, (if the temperature gets even hotter the fan kicks in too a second level?) when the temperature returns to a normal level the fan switches off.

My car
When my car overheated friday, then again on sunday my aux fan never came on, however it does work since when I turn my ac on it blows plenty of air.

My theroy
This leads me to belive my aux fan thermal switches do not work.

Is there any way to test them other than forcing my car to overheat then hoping they turn on?

I would like to have my electric fan run most of the time, aux fan run when nessecary, and engine not blow up.

switches, relays etc are still a little over my head. (Audio systems however are not go figure.)

[tonytony]

bump thread revival, i'm confused with this also

[luvin my 325es]

You are correct. They are two speed fans. It should run low speed when a/c is on.
Maybe take out the switches and put em the oven at 225deg.
check em with ohm meter .
You can unplug the wires from the high and low switches on the radiator,run a jumper between wires and fan should run.
Even better, rewire it to the dash ,next to hazard switch and manually turn it off and on/high low.

[tonytony]

i would like to have them turn on automagically, i'll search around the tread some more without the ac being on since i deleted it. thanks

[brandondan1]

So, the fan clutch is supposed to run on high speed all of time regardless of temperature, while the auxilary fan cuts on according the the thermo switches?

[tonytony]

i'm not trying to insult you, but maybe youre mistaking the fan clutch in the engine bay for the fan in front of the radiator?

[nefarious7907]

I dont have my ac hooked up but I hit the AC button every now and it turns the fan on low to keep the temp in check.

[tonytony]

hmmmm mine doens't spin at all, i think its dead, damnit

[trent]

hmmmm mine doens't spin at all, i think its dead, damnit

There is a low speed resistor. Probably just needs to be changed.

There are 2 fans on the E30. A clutch fan that works off the radiator temperature, when the air gets to a certain temp, it locks the clutch fan.

The aux fan is based on a temperature switch in the radiator. If you use the A/C button to turn it on, this in effect overrides the temp switches.

[tonytony]

thanks trent i'll check that out

[StereoInstaller1]

Maybe take out the switches and put em the oven at 225deg.

No! Try this. Grab a coathanger, a candy thermometer, a 2 quart pot (1/2 full of water, boiling) a voltmeter and your switch.

Bend a loop at the end of the coathanger to attach your switch, so you can dip the end of it in the boiling water. Check your switch with the DVM set to continuity. You should see the switch close at 190°f.

Luke