Rooftop Air Conditioner Install on a DIY RV Promaster Camper Van

Many people build out an RV van on the Promaster platform without installing any air conditioning. Others build and try to put in a household AC unit. We prefer the robustness of an RV air conditioner, designed for that environment, and installed on the roof to save precious inside space.

We chose the Coleman Mach 8 Cub Plus 9,200 btu AC unit for our DIY RV van build in our Ram Promaster van. This unit is a very low profile unit (about 9″ above the roof level), and the power consumption allows us to plug into a standard 20 amp circuit if needed.

Our plan is to travel to locations that have cooler temperatures, but often in the summer, just trying to leave Oklahoma would require one or two nights where the AC would be quite helpful until we progressed further north. For this reason, we did want to install an AC system, but plan to only use it when plugged in to shore or campground power. We did not want to try to design our battery bank that could support the huge load of an air conditioner.

The Ram Promaster van has a fairly flat panel in the roof just behind the cab seats. This location seemed to be an ideal place for our roof top unit. We did move the unit slightly to the driver side to allow more head room on the interior when entering or exiting the sliding door or slider. The inside trim panel extends down from our finished ceiling by about 1.5 inches.

Once we decided on the AC location, we build a wooden from on the inside van ceiling to help support the weight, distribute the weight to the roof frame members, and provide something to attach the finished ceiling planks. The RV AC units use a standard 14 inch x 14 inch hole, just like our MaxxAir vent fan over the rear bed. Our frame was built with pocket hole screws, wood glue, and glued to the van metal ceiling skin with adhesive.

AC support frame, primed and installed.

After the wood frame was installed, we drilled 4 small marker holes at the corners of the frame through the metal roof skin. Then, up on top of the van roof, we marked lines between the marker holes and cut the hole with a quality metal jigsaw blade, similar to the blade used for installing our RV awning windows. We had also coated our roof with white Tropi-Cool paint, so we used a brush to finish coating the roof around the hole and the primed the metal edges.

Painting the Tropi-Cool roof coating around our AC hole.

Back inside the van, we finished gluing in our sheep’s wool insulation (from Havelock Wool) in the ceiling. We covered this with a thin, breathable nylon fabric layer to hold it in place. Then, the wood ceiling planks could be installed around the AC hole.

The AC hole from below with wool insulation around it.

Once the wooden ceiling planking was installed in the RV van, we lifted the air conditioner outside unit up onto the Promaster roof. This was no easy task. It took a couple of ladders and a couple of strong backs, but we raised the air conditioner unit without incident. After the unit was on the roof and aligned with the hole, we could attached the inside ceiling bracket. The unit is essentially held in place with 4 large bolts that clamp the unit down and sandwich the ceiling area between the unit and the bracket. There is also a foam seal that is compressed to prevent water from penetrating into the RV van.

Ceiling clamp/mount trim with the 4 bolts installed.

Once the unit is mounted, there were just a few additional steps to wire the unit and attach the duct and unit trim. The instructions from Coleman were straightforward and we soon had cold air blowing in the RV van!

Air conditioner ceiling vent and controls.
Coleman AC top compressor roof unit.

Products and tools used in this project:

Coleman Mach 8 Cub Plus9,200 BTU air conditioner unit for our van
Jig SawUsed to cut the roof hole (14 x 14)
Metal Saw BladesA quality blade makes the job easy
Painters TapeProtects the paint while using the saw
Masking PaperKeeps metal shavings from sticking to the roof
Henry Tropi-CoolWhite, reflective, heat reducing roof coating
Havelock Wool InsulationOur insulation choice for the RV Promaster van

We also have produced a YouTube video detailing the Promaster RV DIY roof top air conditioner install that provides more detail. Click the image below to view the video.

Happy Trails…

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