Quote:
Originally Posted by upallnight
What do you mean by "Probe"?
The DME controls the fan speed. That's why when the fan is bad, the DME is the module that you will check for the error code.
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I'm pretty sure OP meant which temp sensor eg the radiator outlet temp but it's the DME that uses a few different inputs to control the aux fan, but that's a moot point.
If the AC ever comes on the aux fan situation is resolved.
You have command of the BLOWER fan speed. If you hit the up button on fan the little bar graph grows and the speed of the blower will rise accordingly if everything is working correctly.
As mentioned, HEAT won't come on when the engine is cold, so something could be confused thinking you are requesting heat even with the snowflake button pressed, so reading of the various temp sensors can help determine what's going on there.
There is surely a flow chart somewhere showing how the blower is regulated from engine temp in heat mode. It sounds like there is something along that line interfering.
Test it this way; cold start set temp to 74 and auto and ac on. See when does the fan kick on: if when the needle on the fake temp gauge leaves the cold zone, it's very likely as I described above.
Drive until fake temp gauge points straight up (means coolant temp between 65-115c), then turn off the car.
Start the car back up, blower should come on immediately as temp will be in the "operational range".
If the symptoms match the description whatever makes the blower not run when heat is called for and engine is cold is almost surely where the fault lies.