High Mounted Brake Light

Joggle the bulb gently in the socket. Those rubber sleeved sockets sometimes have a tendency to loosen up and not make good contact. If bulb is okay, as well as the socket, your next step is to use a test light to check for 12 volts. If there is no power, connect a black temporary test wire to the ground side of the socket, and the other end to a good ground. If it works, then you know it is a ground problem. If it still does not work, then you will need to check to see if it is getting 12 volts. Next step is to do the same with a red test wire to a good 12 volt source and to the positive side of the socket.

Did you check both Ford fuse panels, there is a separate fuse box for trailer lights and there is a good possibility it is wired into that one, (I think it is under the hood, not under the dash).
if it is the same as our 06 Winnie Outlook, there is a separate wire in the harness for this light. Ours is an LED bar, so not likely burnt out.
As Paul said, the Winnebago website is not working properly for the diagrams, but check back tomorrow or phone Winnebago service.

Ken

Does the 3rd light work when you put on the emergency flashers?

It would be the same circuit as the other brake lights (assuming they didn't use combined brake and turn signal lights on the sides). If the other brake lights work, I would suggest checking the connections at them and at the CHMSL (i.e. the third brake light).

You can find the wire diagrams on Winnebago's website. At least you could if their website was working right.

Test light indicates no juice and all fuses and breakers appear good. Not sure which fuse its on.

Have you had the cover off and checked the bulb. It may be burnt out or you may have gotten water inside the housing and the contacts have corroded. I am not familiar with what light housing you have but if it also has a running light feature (on dim when the lights are on) is that working.

Maybe the blub is burned out. Have you checked it?