I am having troubles with my over the stove microwave/convection oven. This unit has an exhaust fan and lights for the stove.

I originally had a problem with the microwave and the unit gave a F7 fault code. I tried it again and received the same code. I unplugged the unit for a couple of minutes and plugged it back in and the microwave seemed to work. I put an 8 oz cup of water in the unit and ran it for 2 minutes. The water did not heat up. One interesting happened while the microwave was running. The lights that shine on the stove would turn on and off automatically. It did not cycle, they just turned on sometimes and then back off. I do not know what this means.

I opened the unit and checked the cooling fan. The ohms through the motor windings were 43 ohms. Seems to be OK. Also checked the capacitor. It seemed OK.

I checked the magnetron and read less than 1 ohm across the terminals and infinity from the terminals to the housing. This seems to be OK.

I visually inspected the relay control board, relay board, and inverter. I did not find any loose wires or burn marks. Also, I checked the interlock switches. They were also OK.

I checked the voltage on the relay board at point 4903-1. It had no power until I opened the door or ran the unit. Then I read 120 Volts. I think this is normal. (Not sure)

I ran the units test mode to check the touch panel and relay control board from the display panel. Everything seemed to be OK. I did a little test on the magnetron thermistor. The thermistor read 25°C after it had been sitting for a while. I ran the unit for 2 minutes and the thermistor read 40°C according to the display panel. I think this means that the magnetron must be getting power to heat up. Not sure on this either.

I checked the amperage of the unit while it was running at 100% power on the microwave. The amps went from 0.7 amps to 5.5 amps. It would cycle evenly up and down every couple of seconds. I do not know what the amp draw should be but that seems a little low.

I think there is a problem with either the control board, relay board, magnetron, or the inverter. I cannot determine which one it is. From the symptoms can it be determined or is there another test to determine the defective part?

Thanks
Steve