There should be a "mini-manual" (tech sheet) hidden inside the unit behind the
control panel or hidden on the left side behind the grille, which is very
helpful when troubleshooting, testing, and locating components. It should cover
an F7 error code.
video is available
showing how to remove a typical over
the range control panel assembly in under 5 minutes.
This may help:
F7 Error Code On Microwave Ovens With Inverter Board
MODELS: GH9177XL, GH9185XL, MH9180XL, MH7155XMS, & KHHS178L for example
An F7 error code could be an inverter board failure. Anything else that
prevents microwave energy may also cause an F7 error, and must be checked. The
technician should perform the following procedure to test for an F7 error code:
1. Check the magnetron.
2. Check the magnetron TCO (it should be closed).
3. Check the 3 interlock switches.
4. Check the harness wiring.
5. Check the electronic controls.
6. Check the inverter board.
You can find links to helpful exploded view diagrams and
part ordering help
I recommend that you bookmark that link to your favorites.