Who makes the best one other then making your own? I like the jet one(i think its the jet) that just replaces the one in the block and sends the fan on at a lower temp. What does it really do? Does the computer read resistance of the sensor and it puts the fan on? Could I just spice in a resistor in that case? Anyway, whats a good aftermarket switch?

 

The switch responds to heat from the coolant and completes the circuit. Sometimes people who don't really understand how electronics work just ground the relay when they can't figure it out. Then the fan runs all the time. When I bought my 'maro it was rigged like that. After about five minutes I saw the secondary fan switch was not plugged in. I have since seen too may 3rd Gens rigged the same way.

BTW, the computer has no control over the operation of the secondary fan...

I have a Hypercrap one and it sucks, turns fan on after 3 min of operation and then it never goes off!!

 

which one did you get? the 200* fan looks like a good buy and wont be on all the time.

 

I bought the switch they recommend for using with a 160* stat. Now I have a 180* stat, but the stupid fan comes on too early. I guess the stupid thing is broken. At least it comes on though...