No sure how to remove oven from under cabinet in motor home

Convection needs fan drive to force the air into the oven cavity. The fan may be direct motor drive or belt driven. If the latter the belt may be broken or simply have stretched and come off.
Before removing the cover of the oven in attempt to carry out any maintenance such as replacing the Oven cavity lamp, make sure the oven is disconnected from the power point ! The voltages in a microwave oven ARE LETHAL !

Probably is the fan tapping something. Power it down/DISCONNECT power. pull unit and if there is a cover, remove it. look for the convection fan and see if it free-spins. should find spot where it is hitting and could be adjusted.

It needs the capacitor and magnetron replaced. there could be more issues like a burned wire so have a look while the cabinet is open

The megatron tube is not working. The microwave should turn off when the door is opened for safety. If it is still under warranty, return it. If not, you may consider replacing the unit. I know its expensive, but its just taking up cabinet space tonight.

LOOK HERE;

http://www.serenitysys.com/******/archives/GE%20RV%20Microwave%20manual.pdf

change the tube/heating element

We put false doors on the back of the peninsula, mounted the wall mounts on the inside of these doors and then connected it to the top.

yes its possible

Hi,
Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Microwave Oven Basic Troubleshooting Tips
http://www.fixya.com/support/r5508031-microwave_oven_basic_troubleshooting

heatman101

Remove the face plate above the door. You will see two bolts where you can use a screwdriver to turn them (unlock them). Those bolts go all the way to the back of the microwave. Once you have turned them (you do not need to remove them), you will need to remove the one - three screws that come in from the cabinet above. You may have to jar it loose if it still stuck.