For an electric fan you want to check the temp of the radiator or hoses, not the engine temop

checking temp at the head means the switch doesn't happen because the head/block temperature is regulated to a certain temp -- so it's always going to be around 72C when the engine is warm

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Ah right I get it. That picture is of a little $2 thermal switch, they have a cut in and cut out, usually something like 80C on - 70C off, depending on model. It's something you might use instead of the controller.

The ebay controller has a probe that could also be cable tied to the lower radiator hose or jammed in the radiator somewhere near there. Might read a little inaccurate though.

Well the eBay controller is adjustable, is it not? I would use the sensor that comes with it. Never seen that kind before so don't know exactly how it mounts up but it's got to measure the radiator temp somehow

So could cut the sensor off the ebay controller and use one of those thermo switches. Rating for the temperature switch might be about 80degC? since it's on the outside of the hose it might not match the water temp exactly.

The sensor goes in the lower radiator hose

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Where do you stick the temperature probe? (no funny answers!)

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