Thread: How can I tell if my electric fan is drawing too much current.

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here is a way to do it with two temp sensors and two relays. The low temp sensor is attached to the coil of the first relay which provides power to the second relay. The second relay uses the normally closed contact to power the low speed fan circuit. When the temp reaches the set point of the high temp sensor, it completes the power to the coil of the second relay and moves the contacts so that the normally open now has power for the high speed fan. Also, at the same time, the low speed contact is opened so the low speed fan circuit loses power.