If your question is ‘Will a 12V DC fan run backwards if the wires are reversed?’, the answer is yes. If your question is ‘Will this cause the vent to exhaust into the coach?’, the answer would be no. As Tom says, the microwave vent system has to be baffled for one or the other.
I think Tom has the answer. Check the installed model number against the parts book to see if it has been changed. It could be the same model that was original in the coach and if it is, I believe that they can be configured to vent inside or out. If it has been replaced with a different model, look up the service manual for the installed one and it should show whether it can or cannot be configured for internal or external venting.
Ours is a 2004 and came with the Sharp R-1874. It made an awful noise in the beginning, which turned out to be microwave parts vibrating against each other and the mounting frames. After removal and the addition of several sticky back foam insulating pads on a few surfaces, the rattles are gone and the vent works just fine.
Yep, ours rattles also. Driving down the road or just parked with a wind on the side. For long trips, I do something similar to what ernieh does. I have a piece of foam that I wedge into the outside to hold the flap closed. Mine takes a ladder though.
Would you happen to have pictures of your two handy items? Dony gets the job of climbing up to clean the camera and I’m sure she would welcome a better way to clean it. I get the job of installing and removing the foam for the vent flapper and ladders are becoming scary things for me.
Have Fun!! Mark & Donalda 04 Horizon 40WD no TOW 90,900+ miles and counting
Triumph Bonneville & Susuki S40 on the back