Double temperature switch

[oldtimer]

Can someone educate me where and what does item 10 does on the link.  Does it send a signal to what?  What part of the cooling system it monitors and is affected by it?  It has power when the ignition is on, the green wire.  The previous owner used it to power the electric fan so when the car is running the fan is constantly running.  What is affected if it is bad?

http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=17_0099&hg=17&fg=05


Ben

[e9nine]

On a stock car it runs the aux fan infront of the radiator. It has 2 zones and triggers a low and hi speed for the aforementioned fan. It works off radiator coolant/water temp. If it's bad, the fan will not kick on at those speeds.
Take note, this same fan also turns on when the a/c is running.

In order to run a manual trigger for the aux fan, you use those same wires.

Hope this helps.

G.luck

[oldtimer]

That helps a great deal.  Because the A/C does not kick in when I turn it on, usually if the compressor is bad or low charge the fan will still turn on.  As I mentioned nothing happens when I turn on the A/C.  I will look towards this switch as the reason why the fan or the A/C compresson does not engage.   By the way I frequent other forums, by far this is the one I visit more often.  Thank you who ever is resposible for having this and for us to use a tool to dicuss matters about our cars.  

Ben

[tjts1]

Because the A/C does not kick in when I turn it on, usually if the compressor is bad or low charge the fan will still turn on.  

On every car I've worked on (volvos and toyotas) the clutch won't engage if there is too little gas in the system. My friend has this very issue on his Camry the other day. Clutch wasn't engaging and he suspected some electrical faul. I suggested charging the the system. Sure enough after the first full can of R134 the clutch kicked in. After the second can the needle on the hose started moving into the green and the vents were blowing ice cold.
Obviously there are exceptions to the rule and this was an R134 system but most AC systems have a built in pressure switch that will disengage the clutch if the charge is too low.

[oldtimer]

On my 1984 318i when the charge is low you are correct by saying the clutch will not engage.  However the fan should still turn on when the A/C is turn on even if the chartge is low and the clutch is not engage.  On the other 318i I have the fan does come on even though the charge is low and yes once I induced more charge to it the compressor clutch engaged.

I was troubleshooting the system and wondered why the fan did not come on when I turn on the A/C I suspected it was not going to run but I was  hoping the fan did.  On another note the aux fan at times can be used when sitting in heavy traffic to help cool the car.  Hence that is why it should turn on when the A/C is turned on.  Thank you for the inputs I think I found the problem, this switch.

Ben