I asssumed the switch was bad and jumped the two terminals (fan always on when key is on). But I tested the switch out today by boiling some water and probing for continuity. Sure enough, it passed this temp test.

Subj: Cooling Fan Temp Switch/Sensor
Location: Next to Bleeder Valve

Prior to jumping this switch, I only ever ran the engine while in park, and now I wonder if it ever even got hot enough to trigger the fan going on (I had used the "feel-the-upper-rad-hose-for-warmth-and-the-fan-should-come-on-after-the-engine-shuts-off" test). But the fan never came on so I jumped the switch. I was just about to purchase a new fan switch and discovered that there is continuity there at approx 200F, which I did not expect to happen.

I did notice that the prior mechanic had put what looks to be plumbers putty (gray colored thread sealant) on the sensor threads. I wonder if that putty has interferred with the operation of this switch? Opinions please?

Is there a torque spec for this sensor? ... Specific ft lbs please?

 

As long as the fan operates with the AC on, everything is "hunkie-dorie". I once operated a '69 Saab with a non-functioning fan switch for one year and only experienced "mild occasional" overheating. IMO, the mechanic used a good substance on the threads and that nothing is wrong at all.