What does the reset button do on a fan limit switch?
I don’t know of a “reset” button. There generally is a button on the bottom of the switch that, when pushed in, will close the switch inside and turn the fan on. It will not turn off until the button is pulled out.
shuts the furnace down when overheated—can be a defective limit switch
I would be very leery of using a “reset” on a fan-limit switch.
That sound much like dangerous to me.
Your fan limit switch may be a manual reset high limit switch or roll out switch. Does it look like one of these?
It is NOT a re-set switch.
It may look like one, but it is not.
It is a fan switch that keeps the fan on all the time when activated.
?like a manuel over ride switch in an oil furnace? mine had a white button that you pulled out to bypass the t-state and kick the furnace on, and push it in to put it back to “auto” and let the t-stat work.