A couple of L brackets secured to the wall, some zip ties, a dual throw/single pole switch and an in-line fuse.
Fan from Ebay (MyNewFan), Electronicshaus.com, 120mm (4.75") ball bearing, 90cfm, .18 amps.
Clicky It barely fits. The top of the fan fits between a couple of the exterior vents. If it didn't lay that way, it wouldn't fit. I realize some flow is sacrificed due to my bracket arrangement. I might have been better off with two, smaller fans, but here we are. If two fans would push more air and/or draw less current, I'm open to suggestions. I found a route for the wires into my under-step utility area, but I got impatient about drilling a hole and figured good enough (which never is) for now. I used a dual throw switch because I have a snap switch, 85 degrees, for the other power source. The DTSP switch permits a constant ON over-ride, OFF or thermostat controlled. I haven't installed the snap switch thermostat, yet. It's on the list. I understand you need to secure the snap switch to metal for proper function. Any suggestions or hints about that would be cool, too.
I finished my abbreviated install the night before a trip, with a flashlight. Raise your hand if you've had to complete a last minute project in the dark, on a ladder, while your SO bounces the camper around loading stuff and asking questions about spare keys or other annoying stuff.
The red, ring terminal is the fan's ground. I used a two-into-one splitter off of the existing, positive 12 Volt to gain a terminal for the in-line fuse. It can be disassembled with no evidence of its existence.
'13 F250XL SC gas 4x4 8', Camper & Plow packages, StableLoads, LT285/65R-18 Goodyear Wrangler A/T Adventure, 18x9 Ultra Motorsports "Phantom" wheels
'12 Wolf Creek 850 TC Coleman Polar Cub 9.2k A/C, 90 watt solar, dual propane & batteries, Maggie Rack