I would suspect a blown magnetron thermal cutout or thermostat (whichever it has) or cavity thermal cutout or thermostat (whichever it has).
should also be a "mini-manual" hidden inside the unit behind the
control panel or hidden on the left side behind the grille, which is
when troubleshooting & testing.
, we now have a video available showing how to remove a typical
over the range control panel assembly in under 5 minutes.
If you'd want to scan and e-mail or copy and fax the mini-manual (or at least the "schematic diagram page) to me, I'd be happy to make more precise suggestions.
You can usually find helpful exploded view diagrams and order parts by entering your full model number here
And you'd pretty much need to remove it from the wall and take the cover off to access either of these suspected parts.
Feel free to contact me directly
for more information & help.We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.
William E. Miller