Replacing an RV roof vent fan

One warm May day in Larkspur, Colorado, I turned on the fan in the kitchen ceiling of our fifth wheel and opened the roof vent and some windows to bring in cool air and push out heat. When it came time to turn off the fan and close the vent, the blades kept spinning and the vent remained ajar. No matter which button I pushed on the wall controller, the fan didn’t get the message that it was supposed to stop revolving.

Bob identified the fuse that controlled the fan and removed it from the RV’s circuit panel. The fan went off…and so did the refrigerator. Clearly, that was not a long-term or even short-term solution. 

Troubleshooting

Bob got out his tools, climbed onto the kitchen island counter, and removed the screen over the fan blades, as well the shroud in the ceiling, to expose the motor and wiring. He disconnected the wires powering the unit, put the other parts back in place, carefully got down, and reinserted the fuse to run the fridge. We’d have to function without the vent until we could fix it.

Internet research revealed we stood to risk the least by ordering a replacement wall controller for $40. If that corrected the issue, we’d save about $200. The part arrived, Bob replaced it, but the fan still wouldn’t turn off. 

He took apart the unit again and, using his multimeter tool, determined the circuit board was bad. We could replace it for around $170, or we could change out the entire roof vent fan for about $200. We opted for the latter. 
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We liked the roof fan the factory had installed in our rig. It featured a rain sensor that signaled the vent door to close when wet. So we ordered the same thing from etrailer.com, a Maxxair MaxxFan Plus 4-speed roof vent, and had it sent to an upcoming stop. 

Removal

Before we could install the new unit, we had to remove the old one. That meant pulling up existing self-leveling caulk from around the exterior of the vent. Early on a June morning in the middle of Louisiana, Bob climbed onto the roof and put his oscillating multitool to work to break apart the gummy caulk. 

The buzzing overhead pulled me from my dreamy slumber. I rolled out of bed and went to help Bob, serving as his apprentice. Once he cut through enough caulk, we were able to lift the old vent out of place, exposing a large hole in the roof. More caulk clung to the rubber membrane surrounding the hole and had to be removed to create a level surface for the new unit.

The oscillating tool helped clear away the outer portion of sticky substance from the rubber roofing while I used my fingers to painstakingly pry the tacky residue from the inner square, where the vent had been attached. We swept away any remaining debris, and Bob added a fresh layer of non-leveling caulk around the inner square, in preparation for attaching the replacement vent. 

Installation

With that done, we put the new unit into place. It fit perfectly. Bob reinserted the original screws to secure the vent to the roof. Using a caulking gun, he covered each of the 16 screws with a dollop of self-leveling caulk. Then he traced the edge of the vent unit with caulk and continued adding the substance until every portion around the vent cover was concealed.

Inside the fifth wheel, Bob removed the fan screen and shroud to expose the wires, connected them to the circuit board, and turned on the fan. The test proved successful. We could turn the fan both on and off with the wall controller. Bob put the shroud and screen back into place, and we have an operative roof vent fan once again.

In hindsight, we should have verified that the new unit worked before we sealed it to the RV roof. Thankfully, it functioned as intended, with no issues. 

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