Replacing a 14x14 RV Roof Vent with a MaxxFan

Swapping a plain 14 in x 14 in roof vent for a MaxxFan is a common first upgrade, and most of the job is the same as any roof vent replacement: out with the old, clean, seal, screw down, wire up. What is specific to MaxxAir is the fit checks, the sealant warning, the wire color and the trim ring. This guide follows MaxxAir's installation manuals for the MaxxFan/MaxxFan Plus (P/N 11F90000K) and the MaxxFan Deluxe (P/N 11E90001K), with Dicor's sealant directions for the roof side.

Before you buy: four checks

1. The opening. Remove the interior garnish (trim) ring of your old vent and measure the ceiling opening. It should be 14 in x 14 in. MaxxAir also suggests checking by sliding the MaxxFan's garnish ring into the opening.
2. Roof thickness. The MaxxFan and MaxxFan Plus are designed for roofs 2 in to 6 1/2 in thick; the Deluxe for 1 1/8 in to 6 1/2 in. If your roof is thinner, MaxxAir says to build up thickness at the ceiling opening with wood or another suitable material.
3. Room behind the vent (Deluxe only). The Deluxe's louvers face the rear, so MaxxAir requires at least 8 in clear of air conditioners, storage boxes and other obstructions behind the rear edge of the existing vent flange. It must be installed with the rain shield toward the rear. No room? MaxxAir recommends a MaxxFan or Plus with a FanMate cover.
4. Power. A plain vent usually has no wiring. The MaxxFan, Plus and Deluxe each need a 12 V DC circuit of at least 5 A, wired with stranded wire of the proper gauge. Confirm the circuit you plan to use can take the extra load.

Not sure which model? See MaxxFan Deluxe vs Plus vs standard.

What you'll need

• The fan. If it's a MaxxFan or Plus and you want to leave it open in the rain, a FanMate cover too.
• Butyl tape for under the flange, such as Dicor butyl seal tape (1/8 in x 3/4 in x 30 ft).
• Sealant for the screw heads and flange edge. MaxxAir's MaxxFan/Plus manual names "Dicor self-leveling lap sealant or similar caulking": Dicor Self-Leveling Lap Sealant.
• Or both in one box: the Dicor Seal-Tite rooftop accessory install kit, which Dicor makes for replacing any rooftop accessory.
• A plastic scraper or putty knife, a roof cleaner safe for your membrane, a screwdriver, a caulking gun, a ruler and a fine saw or knife for the trim ring.

Our MaxxAir roof fan kits combine a fan, its FanMate and the Dicor install kit in one cart.

A warning about sealants

Both MaxxAir manuals say to use only a caulk or sealant compatible with the plastic flange and your roof surface, and not to use materials containing solvents such as or similar to xylene, toluene, methyl ethyl ketone, acetate or acetone, which can damage the flange. Polysulfide (Thiokol) sealants must also be avoided. The MaxxFan/Plus manual names Dicor self-leveling lap sealant for the screw heads and flange edge. The Deluxe manual, for its separate roof flange, says outdoor silicone sealants such as G.E. Silicone II have proven suitable, and to contact your RV maker if in doubt. On a rubber (EPDM) roof, follow your roof maker's advice on silicone, and ask us if you're unsure which product to use with the Deluxe flange.

MaxxFan and MaxxFan Plus: step by step

1. Cut the power. MaxxAir says to disconnect main vehicle power before connecting the fan.
2. Remove the old vent and all old roof sealant for at least 2 in around the opening. Clean the area with a cleaner safe for your membrane and let it dry. See resealing by roof type if you're not sure what your roof is.
3. Dry-fit and trace. Center the MaxxFan in the opening with the lid hinge toward the front of the RV and trace around it to mark the area that must be clean.
4. Butyl the flange. Apply a continuous strip of butyl tape to the underside of the flange, covering the screw holes.
5. Wire it. Using the insulated 16-gauge connectors provided, connect the vehicle's 12 V supply to the two fan wires on the driver side. Note the polarity: MaxxAir says the fan's black wire, the one with a (+) tag, goes to the vehicle's 12 V positive.
6. Set and screw it down. Lower the fan into the opening, hinge forward, with the wires going inside and not tangled. Drive the sixteen screws provided at the raised ring dimples around the flange. Don't overtighten; MaxxAir warns it can crack the flange.
7. Seal. Remove butyl that squeezed out. Put a daub of Dicor self-leveling lap sealant (or similar) over every exposed screw head and run a bead of about 3/16 in around the outside edge of the flange.
8. Test. Restore power. Every model except the 4301K and 4401K beeps to confirm power; remote models also close the lid. No beep: go back and check the connections and that 12 V is on.
9. Trim the garnish ring. Most roofs slope, so measure from the ceiling to the fan's control plate at each corner, and cut the garnish ring 1/4 in to 1/2 in longer than each measurement. (MaxxAir's example: 3 1/2 in measured, marked and cut at 4 in.) Fasten it with the screws provided, tucking excess wire inside.

MaxxFan Deluxe: what's different

• A separate roof flange goes on first. Place the Deluxe's Roof Receiving Flange in the opening, centered, with its metal clips facing the sides of the RV, and trace around it. Apply sealant inside the traced area, screw the flange down with the screws provided, and seal over the screw heads and around the flange edge.
• Wire with the lid open. Open the fan fully first (on non-remote models, pull the knob out to unlock it before turning). Same polarity rule: black wire with the (+) tag to positive.
• Lower the fan onto the flange with the louvers facing the rear, check the four metal clips are in place, and fasten it with the four 3/4 in #10 stainless screws provided. MaxxAir says to use only those screws.
• Power-on beep: all Deluxe models except the 5301K and 6401K.
• Garnish ring: trimmed the same way as above. Don't probe the thermostat or IR sensor.

After the install

Dicor's lap sealant skins in about 5 minutes and is waterproof in about 4 hours at 50 to 70°F, but takes 48 hours to reach 80% cure and 30 days to cure fully. Some rippling as it cures is normal, according to Dicor. MaxxAir's fans have a self-resetting fuse on the circuit board in the ceiling unit; if the fan stops, remove and re-apply power to reset it. More in MaxxFan wiring, power and controls.

Common mistakes

• Reversing the wires. On a MaxxFan the black wire is the positive one; check the tag.
• Overtightening the flange screws and cracking the flange.
• Using a solvent-based sealant that MaxxAir's list rules out.
• Mounting a Deluxe backward or with less than 8 in behind it.
• Skipping the butyl. The lap sealant on top is the second seal, not the only one.

FAQ

My roof is only 1 1/2 in thick. Can I fit a MaxxFan Plus?

Yes, but MaxxAir says to build up the ceiling opening with wood or similar to reach the 2 in minimum. The Deluxe's minimum is 1 1/8 in.

Can I reuse the old vent's wiring?

A powered fan's wiring can be reused if it's sound and the circuit can supply at least 5 A at 12 V DC. A manual crank vent has no wiring, so you'll need to run a fused 12 V feed.

Does a MaxxFan fit a Fan-Tastic opening?

If it measures 14 in x 14 in and your roof is within the thickness range, the same steps apply. Our older guide on replacing a Fantastic Fan covers repair-or-replace.

Which cover do I add?

A FanMate for a MaxxFan or Plus; none for a Deluxe. See which MaxxAir vent cover fits. Everything is in our MaxxAir collection and Dicor collection. Found it cheaper elsewhere? We'll beat it.