How to Install a New RV Roof Fan

If you’re like us, you may have purchased an RV with really old style 6″ vent fans. Ours sounded like an airplane taking off anytime you turned them on, they didn’t move that much air, and they were prone to leaking. We decided to rip out all of our old ones and replace them with new, larger, quieter fans instead. The following are the steps needed to accomplish this along with lessons we learned along the way.

Things you’ll need

Step 1: Turn off the batteries

This step is fairly obvious but worth mentioning any time you’re working with things connected to electricity. Even if the fans are only using 12v, it’s still worth the effort to be safe.

Step 2: Remove inside cover

Most fans have an inside cover/house covering the details of the wiring and making everything look “pretty”. This cover needs to be removed before anything else can be done on the fan.

Step 3: Cut wires from old fan unit

Don’t cut too close!

Again, this step is pretty straight forward. Just a reminder: don’t do this until step 1 is done, otherwise you could potentially hurt yourself or damage your RV’s electrical system if the wires happen to contact something you don’t want. Another tip is to make sure to leave some extra wire coming from the old unit. There’s a chance you might have to stop what you’re doing in the middle, or need to use the old fan before the replacement process is complete, so giving yourself an opportunity to hook up the old fan easily is definitely recommended. This also means if the fan you’re removing is still in functional shape, you could sell it on Craigslist without the buyer giving you an evil eye for cutting the wires too short.

Another thing to take note of: check what color the wires are on the old fan and what color the ones coming from the coach are. For us, the wires from the coach were blue and green, but the wires on the fan units were both black and white. If you buy a fan that’s not reversible with a switch, oftentimes you can just reverse the wiring to get the fan to run in the opposite direction. Check the manual of the fan you purchased for more information.

Step 4: Remove screws / rivets

This step should be prefaced with: if you or another owner added tape over the seams before, you’ll have to remove the tape to reveal the fan’s rivets/screws.

Removing the tape from Tips for Re-sealing an RV Roof

If you have rivets, you’ll need a drill bit to drill the rivets heads off and let the rivets pop out. You could also use a “rivet remover” tool. We found using a drill bit worked just fine for us.

Step 5: Remove the fan and clean the area

Taking out the nearly 30 year old fan unit

Next step is removing the old vent fan unit from the roof all together. For us, this was a little easier said than done. Ours had been covered with numerous layers of roof coating, so it took a lot of scraping/chipping/cutting/prying to get it off. This is definitely one of those steps you see in an article like this and don’t get fair warning on how tricky it can be, so be warned, this may be harder than the few sentences I give it here do it justice.

Step 6: Apply Butyl Tape

Applying the butyl tape

This step is fairly straightforward, but worth calling out on its own given how important it is. Butyl tape is the first line of defense against water getting into the RV, so having the previous steps done to ensure it has a clean surface to seal against is important. Make sure the tape is firmly attached to the unit before removing the backing.

Step 7: Insert fan unit and screw in

Again, this step is pretty straightforward. The thing to keep in mind when putting the unit into place is to do as much as possible to align the fan with the hole and the fan’s final placement before letting the butyl tape stick. It’s hard to adjust the placement of the fan if any of the tape gets a good hold, and you won’t be happy to have to re-clean the opening and reapply a new strip of tape if you mess up.

Step 8: Apply lap sealant and/or vinyl tape

Some instructions to be extra safe advise putting a small drop of lap sealant on each screw head to help prevent moisture from entering. We decided to use Eternabond vinyl tape and skip the lap sealant. We’ll see if that was a wise decision or not over time, but the vinyl tape has treated us well since we’ve used it on another fan before.

Don’t forget to peel off the protective plastic cover!

Step 9: Connect wires

Now comes the fun part: hook up the new fan’s wires! If you followed step 3 correctly, you should already know which wire is which coming from your coach. I used heat shrink connectors as that’s what had been used at one point and makes a good seal for wires that might be exposed to the elements.

Step 10: Cut inside cover to size and attach

The inner shroud/cover is made very large to fit a variety of RV sizes and roof depths. For ours, we have to cut off about 3-4 inches, which is easiest done using an angle grinder. Once that’s done you can just insert the shroud and the screws to hold it in place.

And voila, you’re done! It takes a few steps to get everything done, and some attention to detail, but overall, the process is simple and easy to complete on your own.

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