Heater Blower After-run Temp Switch
 

Can someone tell me the function of this switch? Is the heater blower on the engine supposed to keep running after engine shut down when hot? If so, (mine doesn't) what is best method to test?

Bump
 

Does the CHT sensor or ECU control the operation of the heater blower after the engine is shut off? Is the 'heater blower after run temp switch' a sensor in itself? :confused:

I can't find a whole lot of info on this switch via search or the bentley manual... TIA.

Yes, that is exactly what the switch does, if you are referring to the one sitting on the oil breather. If you shut the engine down and the temp switch is too hot, the blower fan will continue to run to circulate air.

ianc

ok thanks ianc. I just noticed that mine is running when the car is stone cold and I turn the ignition switch to on, so there is something going on there.
I have a big problem I am trying to solve, so this may be another clue...
http://forums.pelicanparts.com/porsche-911-technical-forum/365365-3-2-carrera-wont-go-past-1500rpm.html

I am trying to figure out whether or not this switch failing can cause my other bad running problems, or if it is a result of my other problems (cause or effect). Do you know if it is possible that the ECU or AFM function are affected by this switch going bad or giving false readings, or does it only 'talk' to the blower fan??

The DME and AFM functions are not related in any way to this. The AFM has its own integral air temp sensor to help it calculate air density from volume, and the DME makes use of the CHT to calculate engine temp.

If your blower fan temp switch is bad (constant open), then that could cause your problem. Check continuity across the switch when cold.

ianc

OK, I just thought that maybe the DME might get input off of this switch, and be trying to correct the non-existent open loop 'hot' condition by manipulating AFM or other engine components in some way, which was in turn causing my other problems.

I hope you can follow that...

Anyway, thanks for the info. I'll check out the switch and replace it if it's not working right. SmileWavy