Cooling system questions: Fan, t-stat, rad

[azruss]

When you plug the fan back in, does it start running.

[KevAndAndi]

When you plug the fan back in, does it start running.

Indeed. I tried it last night. Days later, cold engine, and the fan wants to keep running.

[RRoller123]

The fan is always powered, so it is shorted to ground, likely right through the temp sensor at the bottom of the radiator. Sounds like a new sensor is necessary, unless the fan was bypass wired and that is screwed up somehow, or the switch left in he on position. I have a bypass switch from a PO that I just left in, but I never touch it.

[azruss]

you can test the temp switch in the bottom of the radiator. disconnect it and test across the 2 leads with a ohmmeter or continuity tester. should be an open circuit cold and closed circuit hot.

[KevAndAndi]

The fan is always powered, so it is shorted to ground, likely right through the temp sensor at the bottom of the radiator. Sounds like a new sensor is necessary, unless the fan was bypass wired and that is screwed up somehow, or the switch left in he on position. I have a bypass switch from a PO that I just left in, but I never touch it.

Thanks. When we got the car in October, the rad fan was working normally, or close to it. There's no obviously funky wiring.

I just got a FedEx notification that the new thermoswitch is sitting at my back door, courtesy of Autoricambi. If I have time this weekend, I'll take this opportunity to drain the cooling system, R&R the thermoswitch, install the coolant hoses portion of my silicone hose kit, and install my shiny, new aluminum throttle heater cover and stainless steel heater pipe from Allison's. Then I will flush the system via the Prestone T and refill it.

This is the first time I will have refilled and bled the cooling system. The bleeder screw on the new throttle heater cover should help in that regard. If I'm not mistaken, that new bleeder screw will be situated at the highest point in the system - perhaps higher than the Prestone T.

Question: Should one put Teflon tape on the threads of the rad fan thermoswitch?

[KevAndAndi]

you can test the temp switch in the bottom of the radiator. disconnect it and test across the 2 leads with a ohmmeter or continuity tester. should be an open circuit cold and closed circuit hot.

I will do that tonight to be certain that this is a switch failure. Thanks.

[KevAndAndi]

Yup, the old fan switch is showing continuity (closed switch cold) and the new switch shows no continuity (open switch cold).

[RRoller123]

bingo