The fan, all interior and exterior lights, water pump, propane and CO alarm, stereo, heater, thermostat, operate on 12V, not 120V. Fridge controls on the inside of the camper need 12V, controls accessed through the outside vents generally do not. Water heater may or may not need 12V, depending on model (automatic ignition does need 12V).
Basically, everything except the converter, air conditioning, microwave, and stuff plugged into the household outlets take 12V or no electrical power at all.
In a pop-up, 12V stuff in the roof (vent fan and lights) runs through a safety switch to prevent being powered when the roof is down. That switch makes a connection when the galley is set up (in most models). In Forest River A-frames that safety switch is located at the port forward corner of the box, and makes the connection when the forward roof panel is lifted up. The safety switch would be among the list of things to check.
The vent fan usually has a safety switch to prevent fan operation if the vent cover is closed. On my A-frame that switch doesn't allow the fan to come on unless the cover is opened a couple of inches.
In your photo of the fan, there is a fuse (I think mine is 3 amp). It's located to the top and left of the fan control in your photo.
In your fuse panel, usually one of the fuses (not circuit breaker) is for all the stuff in the roof. Probably a 10 amp fuse for most pop-ups.
- You must have a charged battery installed, or the trailer must be plugged in and the converter working. Measure voltage at the battery cables to confirm 12V-14V. The figure will be 13V+ if the converter is charging the battery.
- if you have 12V power, see if the overhead lights and/or fan works. If one works but the other doesn't the problem is the one that doesn't.
- If you have both fan and overhead lights not working, check the safety switch mentioned earlier.
- If the safety switch is good, check the fuse panel for the fuse that controls the fan and overhead lights.
hope this helps
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time