Eike

Hi,

I hope my question is simple: Where is the "cooling fan temp switch" located if a '85-'89 C4 is equipped with the B4P-option (dual fan)?

So a non-B4P Vette does neither have the switch nor the dark green wire, right?

RePete

passenger side head in an '85.

blackozvet

low temp fan switch is passenger side head
high temp fan switch is on driver side head

gerardvg

Hi

The temp sender is between cyl 1 and 3. The temperature overide for the booster fan switch is between cyl 6 and 8. on my 85

The Ecm controls the main cooling fan via the engine temperature, it will turn the main cooling fan on at around 228F

The booster fan comes on at around 235F (don't quote me on this is a rough guess we Ausies use celsius not farenheight)
The switch for the booster fan a has a big round clip, the temp sender is a flat spade one.

RePete

What he said. but please not that the sensor between 1 and 3 is for the gauge only. the ECM get its info from the coolant sensor in the intake manifold (CLT).

gerardvg

Yes the ECM has its own temp sensor, see the image below the blue arrow points to it beside the cold start temp switch.

When you use a scanner or tuning software like Tunerpro, you can see that temperature reading. I found it was way off, showing way too low and had to replace it in my 85.