BIMMERMIKE

What should resistance reading be on thermal switch (rear of intake manifold 928 606 217 00) for an 1989 S4?
When I tried to take a reading resistance is infinite.

FredR

Given it is a switch the resistance will be infinity [contact open] or nigh on zero ohms when the contact is made.

davek9

And... one side (wire) should have 12v, when the intakes temp gets too high the "switch" closed and runs the fan(s)

cobalt

I had an issue with mine purchased a new one only to find I had contact issues.

worf928

I’ve had to buy exactly two new ones over the many years of working on 928s: one was indeed dead, the other I broke through carelessness.

So, yeah, they don’t generally die.

928NOOBIE

You will make the mistake of underestimating the punch that diminutive appearing connection has available once. It is an electrical connection that Porsche somehow was able to keep from appearing to degrade at all, no matter how damn rotten your grounds are...