Whirlpool Microwave oven no power

Hi @myth9

Seems as though there may be a problem on the control board.

I cannot find the wiring diagram (Whirlpool part # LIT8171839) for the oven, but with most microwave ovens there's a low voltage transformer on the control board that steps down the incoming 120V AC power supply which is then rectified to 12V DC to power the control board.

If there is no indication of power at all i.e. no control panel display showing the time, as you have checked that the fuse in the oven is OK, check if there's power on the board. It may be that the VR1 MOV varister has blown thereby opening the power supply to the board.

If it is OK it may be that there are other faults on the board which are causing the problem.

All the functions of the oven are controlled by the board operating the various relays on the board which connect the AC voltage to the circuits that use them e.g. oven light, fan, turntable motor, HV circuit etc.

Here's an image of the board showing the LV transformer and the VR1 varister.

If you decide to replace the board search online for 8171857 to find suppliers that suit you best. This is the Whirlpool part number for the control board in your model microwave oven.

(click on image)

Be safety aware when working inside microwave ovens. The HV capacitor can store >5000V DC for months even if the power has been disconnected for this length of time. This amount of voltage can seriously injure you. The HV capacitor needs to be correctly discharged as soon as it is accessible after the oven's cover has been removed and before any further work is done in the oven.