RV Roof Vent Fan Replacement Guide
Your RV roof vent fan has given up the ghost. Perhaps the motor that raises the cover has died, or it has just gotten rusty over time and no longer functions. Either way, you’ve decided the time has come to replace it.
Most current RV fan openings are 14”x14”. These can vary from one RV to another, but this is considered the standard size. You likely don’t want to remove your existing fan before you have acquired another and are ready to install it. The last thing you need is a sudden rainstorm and a 14-inch hole in your roof!
Almost all RV vent fans are 12-volt DC powered. If you have any reason to suspect otherwise, you can remove the garnish or trim ring from inside (this shouldn’t affect the weatherability) and look at the wiring. Use a voltmeter if you’re unsure, or investigate the model of your current fan online for specifications.
For this article and related photographs, we replaced older bathroom and kitchen Fan-Tastic fans with the MaxxFan Deluxe from MaxxAir.
What you’ll need
Before removing the old RV roof vent fan, ensure you have everything that you need to finish the project in a single sitting. You might need a helper for when you are on the ladder or to help you bring the new fan up to the roof and the old parts down.
Here are the basic items and tools you’ll need, though your situation could require additional tools:
- Replacement RV roof vent fan
- Butyl sealant tape (easier to find online)
- 1 or 2 tubes of self-leveling lap sealant (get the right kind for your rig’s roofing material)
- Caulking gun
- Plastic or metal putty knife
- Heat gun or hair dryer
- Grocery bag to collect old lap sealant for disposal
- Extension cord
- Drill or screwdriver, possibly both Phillips and square-head bits
- Roof material-appropriate cleaning product, like mineral spirits, etc. (Check with your manufacturer.)
- Coping saw or equivalent to cut the trim ring to size, if needed
- Stepladder for inside and a full-size (or inbuilt) ladder to get on the roof outside
Removing the old RV roof vent fan
First, and most importantly, remove the fuse that provides power to the fan. You may need to cut existing wires, and safety is important. After removing the fuse, make sure you can no longer power the fan on to verify.
If you haven’t already, start by removing the trim ring from inside. This is likely just four screws, and if your fan was installed at the RV manufacturer, it probably has square bit screws. (This was the case for us, but all the screws with the new fan unit were regular Phillips screws.)
Once you have the trim ring removed, you should be able to see one or two sets of cables, depending on the original fan type. For us, the original fan had an RJ-11 wire and connector (looks like an old-school phone wire plug) from the control panel on the wall to send instructions to the fan, as well as a positive/negative 12-volt power supply.
The new fans we installed have a wireless remote control. We left the old panels on the wall and just tucked the cable inside the roof in case the next fan can utilize it. Leave these wires all in place for the moment. You may have to open and close the vent, depending on the model, to get to the screws necessary to remove the fan’s primary unit.
The next step is to get up on the roof with your tools. Have the extension cord already in place. If you have a helper, bring a rope to be able to pass things up and down. Throwing tools to and from the roof is a very bad idea. Anything not caught can damage the roof surface or you could fall.
Removing the old lap sealant
Lap sealant is a special kind of caulking, and the self-leveling type creates a puddle, ensuring a smooth, even seal (do not use a no-sag type for this application). It must be removed before the existing RV roof vent fan can be taken out. This part took us about an hour the first time, and just 30 minutes the second time.
The easiest way to do this is apply heat and then peel it back. Using a heat gun, about 2 inches above the sealant, apply heat slowly and evenly to a section of the sealant. Turn off the heat gun and set it safely aside. Don’t let the metal end touch anything as it is very hot.
Now, you can start to roll the sealant back with your fingers. Bear in mind, the sealant is also quite hot, and it may need to cool a little before you can handle it.
Using your fingers, you can pull the sealant up, but ensure that the roofing material underneath doesn’t get stretched. Using two hands, you can peel up the old sealant and push down the roofing material underneath.
Work your way around the entire fan, heating it a little, and peel it up to the edge of the receiving flange. You can tear these pieces off as needed and put them into the grocery bag to throw away later. (Don’t litter!)
It’s neat to see the color difference between your exposed roof and the super white parts that were protected by the sealant. That shows you how good this stuff works!
Now you have to reveal the screws holding the flange to the RV roof. If the installation and prior lap sealant were done correctly, you won’t see these screw heads until you scrape away the coating that surrounds and covers them.
This part is quite a bit easier than the previous step. Using your putty knife (we found the metal one perfect), you can scrape away the sealant on top of the flange edge. Just be sure to not slip and damage your roof material. Scrape away all the places there are screws. You might see little raised bumps, but it’s best to only scrape along the flat surface until you hit something, likely the screw.
Different fan installations have a different number of screws. Our old fan had less than our new fan, for example. You may have to have the cover closed or open, depending on the model, to access the screws.
This fan location, for us, was butts up against one of our solar panels, so removing the sealant was tricky, and getting to the screws required a longer square head bit.
Go ahead and remove the screws you can find. Some models (like the new MaxxAir) have two screws in each side that anchor the fan unit to the flange. If you can remove this first, you will have much better access to the flange screws. Take them out now.
Removing the flange and fan
Now that you have the screws removed, and possibly the fan mechanism, you’re ready to begin pulling up the flange. Do this slowly! If it was installed correctly, there is butyl tape between the flange and the roof.
If this is an older installation, it has likely dried up a bit and won’t be too sticky, but you need to work your putty knife (preferably plastic) between the roof and the flange and pry it away from the old butyl tape. Be careful, move slowly, and be very cautious of the roof material during this step. You can also have your helper inside lightly pushing up on the unit from one corner, while you work the putty knife under the edges.
Once you have the entire flange and unit loose from the roof, just set it to the side. You’ll need to go back in now and disconnect the wires or have your helper perform this step.
Return to the roof and move the old fan out of your work area or lower it to the ground with your rope and helper. Keeping the roof and your walking path free of obstructions is key so that you don’t trip while moving around.
Prepping for the new vent fan installation
Congratulations! You have a hole in your roof. It’s time to put the new RV roof vent fan in.
The first step is to remove as much of the old butyl tape as you can. Usually, this will be the black substance stuck to the roofing material. We’ll be replacing it, and we want to ensure a good seal for the new installation. This can usually just be rubbed off with your fingers.
Some will go inside, so be prepared to sweep later. Now use your cleaning solution (make sure it is compatible with your roof material) to clean the area as well as you can.
Remember: All RV roof vent fan covers open with the venting to the back of the rig. Some newer models can automatically open by temperature sensor. You don’t want the lid to be ripped off at 60 mph on the highway because it got warm in the rig. Ensure you understand your new fan’s correct orientation before proceeding.
You can now disconnect or cut the old power supply wiring, leaving as much slack as you can.
It’s time for the new flange to go on, but first, test placing the flange into the exposed opening, making sure it fits correctly. Different models of fans may or may not have the fan, cover, and flange as separate pieces, so you may be testing the entire unit. Also make sure that you’re testing it in the correct orientation for how the fan will ultimately go. While the opening is usually square, in the case of our new fan, there are screw holes in the upper flange area that must be on the left and right, not the front and back.
Next, apply the butyl tape to the flange’s underside edge. By placing the butyl tape on the flange instead of the roof, you can ensure you have a good fit and minimize exposure of tape outside of the edges. We want the lap sealant to go on the flange and the roof, not on the tape.
If your fit is good, you can begin screwing down the flange using the provided screws. The fan’s included screws may have different types and lengths. Consult the included documentation to be sure you’re using the right screws here.
Also, you’ll be making new screw holes into the wood of the roof, but if you are using the exact same locations again, the screws might be loose. You can put the screws into a different part of the flange, but you won’t have the pilot holes to help. We’ll be covering up everything with lap sealant anyway. The screws should be going through the butyl tape you applied earlier, creating a good seal.
At this point, you can place the fan, if separate and necessary, into the flange and secure it according to the instructions provided with the unit. For ours, this was two screws on each side.
Applying new lap sealant
Now it’s time to prevent any rain leakage in the future. Using the caulking gun, apply the self-leveling lap sealant about ¾ to 1 inch to the inside of the flange edge and the same distance to the outside. Be liberal! The putty will eventually puddle and create a smooth seal.
Important: Be sure each screw head (and any unused pilot holes) are covered. Be careful to not get any of the sealant on the fan unit itself that could impede the vent opening and closing. When you believe you have the entire circumference covered in sealant, add a little more to any gaps you see. It really is okay to overdo it, as you’ve seen how it can be removed, and preventing leaks is the most important goal.
That’s about it for the roof work, hopefully. Time to retrieve your tools and trash and return to ground level.
Connecting the wiring
You should now be able to connect the new RV roof vent fan to the power supply. We suggest using a voltmeter on the power supply to ensure you connect positive and negative wires correctly.
On our rig and new fan, the black wire was positive and the white was negative. The new fan’s wiring was labeled, the rig’s was not. Using a voltmeter that shows negative values, we were able to determine that it was indeed the same way for the rig.
Testing the white power supply wire to the positive test lead on the meter showed a negative 13 volts. That lets you know you have the polarity reversed. (Of course, you’ll have to replace the fuse you pulled earlier to test this, if necessary.)
Remove the fuse again, if you replaced it just now. Connect the power supply wiring using wire nuts or included male/female connections. Applying a little electrical tape around the connection is recommended to keep out moisture, but using a proper connector is key.
Reconnect the RJ11 connector if you will be continuing to use the existing wall unit or replacing it with the same style connector and re-using the wire. If the wire and plugs aren’t compatible, you’ll need to use the existing wire to fish the new cable through. (This can be quite difficult, with turns in the frame, but hopefully you won’t have to do this.)
Replace the fuse in the panel to allow power to flow to the unit. Using the control panel or remote (if your new fan is wireless), give it a test. You should have a new working unit.
Inside trim ring installation
This procedure may differ based on the fan model or even the roof position of the fan’s opening. When replacing our bathroom fan, it was more centered in the roof. With the kitchen fan, it was more to the edge.
Many RV roofs are curved, so the trim ring may need to be cut to fit, as was the case with our kitchen location. Follow the included instructions to ensure proper cut and fit.
If the trim was needed and completed, you are ready to place the trim ring. There is a gap between the roof flange and the fan unit that the trim ring fits into. Be sure your wires are tucked out of the way so they don’t get cut in this process by the plastic.
Once you have the trim ring feeling flush to the ceiling, simply insert the four screws holding it in place. This is a great time to have a helper, as you have to hold it up while getting your drill and screws ready. You could possibly use blue painter’s tape, too, to keep the ring in place while you fetch these supplies.
Make sure you keep track of all your RV maintenance and repairs with an online tool such as RV LIFE Maintenance. Not only can you keep all of your documents in one place, but you’ll also receive timely reminders when maintenance is due to help you avoid costly repairs and potentially serious accidents.
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