It starts innocently enough – a space in the roof, a wooden template to get the right hole spacing, then out come the power tools and all of a sudden there’s a 14″ hole in the ceiling.
We knew we’d need a fan to help move air through the van. Because we intend to put a lot of solar panels on the roof, we wanted to put the fan as far back as possible. On a 170 wheelbase van, that means putting it just in front of the rearmost roof rib.
There are some kinks in the roof at that point – you can see them in the piece we cut out – but it’s easy enough to slide the fan housing between the roof and the top of the kinks with a bit of persuasion and some metal bending.
We chose to use a Maxxair MaxxFan 7500K fan. It can still run even if it’s raining (important in the Pacific Northwest) and you can drive with it open (important for forgetful people). It comes with a remote control.
We thought that the remote was a stupid luxury, but with the bench seat in the third row position it’s hard to reach the controls from inside the van. The remote solves that problem pretty well, and it’s actually got quite a sensible button layout and display.
The fan expects to have at least 1-1/2″ of interior depth to slide in to, so I asked my neighbor Ken whether he could put something together for me. He’s a high-end cabinet maker by trade, and he couldn’t help himself. He found some pieces of mahogany in his shop, cut them to size, and used spline joints to hold them together. Even if the multiple levels of waterproofing fail, that frame will still stand up.
It turned out to be really important to clamp the joint before the Sikaflex glue between the wood spacer and the ceiling metal set. The screws from the fan mount did not pull the wood up as tight as they could have, especially through the layer of butyl sealant tape that we put under the fan mount.
Then, we added a layer of Dicor self-leveling lap sealant over all the joints to stop water from even getting near any gaps.
It’s really scary to make holes in a perfectly good brand-new van. It gets easier as you go along though. After doing the fan install, pretty much every other hole we make will be smaller and less visible.
There are full write-ups on how to do this job on the Sprinter Forum.