I have a logik microwave. The microwave began the common issue of having the light turn on dim, turn table turns and the fan spins when the door is open. I went through each of the door switches and everything is fine. I looked at the board and noticed a relay labelled as mains. I measured the voltage across the coil both open and closed doors but it never changed. The voltage between the one coil pin and ground was 13v and the other coil pin and ground was 0v DC. I assumed the coil was meant to be closed and I closed the circuit the relay controlled manually. The problem went away! The door was open when I did this and so the fan stopped, turn table stopped and the light brightened.
Before I try and use it to heat, can someone shed some light on what this relay does. Not connected causes it to behave oddly but the fact that its there tells me its necessary.

I just need to add that even though there is a voltage between the one coil pin and ground, there is no potential difference between the coil pins. Its almost as if the one pin is connected to the positive 13v source and the other coil pin isn't grounded and so the relay controlled circuit isn't closed.