Williams P200200 Fan Switch

Is this switch supposed to be open or closed when you check it with a multimeter?

Since this is a fan switch it is going to be normally open. When the temperature in the unit gets to 120 degrees that switch will close and generally turn on the fan or blower to move the hot air away from the heat exchanger. The switch will stay closed until it senses the air temperature in the unit going below 105 degrees which is the 15 degree differential of the switch.

That is how most fan switches work which is the opposite of a limit switch. The limit is normally closed and when it hits the temp rating it opens until it cools down to a certain temperature. The White Rodgers 3F01 and 3L01 series are some wholesale versions of fan and limit switches.

if we had a multimeter we wouldn't be able to test that without setting up a complete science experiment which is not something we are set up to do here.

I have a new William's wall heater. Why does the fan not kick on before burner shuts off?

Please check with a local contractor or chat with a contractor at the link below. Thank you. https://www.gsistore.com/pages/ask-a-contractor