We're thrilled to be tackling our dream project and converting a Sprinter into a camper van. For this build, we cover how we installed the vent fan, DIY roof rails, and mounted the solar panels onto those rails.
Parts list
Fan-tastic Fan 2250, 100W solar panels, strut channels, strut channel nuts (M8), M8 rivnuts, M8 bolts, Loctite 242, Sikaflex 252, DAP black RTV, OSI white exterior sealant, parallel Y solar connector, roof cable entry gland, 1x2" poplar boards, 1.25" aluminum angle, pop rivet tool.
Fan installation
We chose the Fantastic 2250: 3 fan speeds, reversible direction (pull air in or push it out), and a built-in thermostat, for about a third of the price of the top-tier Maxxair models.
Preparing the roof
The fan ships with a foam template for the cutout, though we found it wasn't perfectly accurate, so we recommend tracing the base of your fan directly. The first-generation Sprinter has a section on the roof, next to the sliding door, originally meant for a factory fan or passenger AC unit, a perfect mounting spot with no interference from structural ribs, and enough distance from where we planned sliding windows toward the back for good airflow.
Cutting the opening
Using a step drill bit, we drilled a ½" hole near each corner so the jigsaw could articulate from one side to the next, then cut the hole with a fine-tooth metal-cutting blade. Cutting sheet metal with a jigsaw is loud. Wear hearing protection. We taped a garbage bag underneath the cut line to catch metal shavings, then sprayed semi-gloss white paint on the bare metal edges before removing the tape.
Building the frame
We cut 1"x2" wooden boards and drilled pocket holes to build a frame that mounts under the fan from inside, sandwiching the roof skin between the fan and the frame, giving extra material for mounting screws and support for finishing trim later.
Mounting the fan
After laying down seam sealer, we set the fan into position with the hinged side facing forward. This matters, since mounting it backward creates a parachute effect at highway speed if left open while driving. While one of us held the wooden frame from inside, the other drove in self-tapping screws (1" would have been ideal; we used 1-1/4" and ground the excess flush with an angle grinder). We finished by taping the perimeter and applying exterior window sealant generously around the seams and screw holes.
Roof rails installation
Rather than off-the-shelf roof rails, we used low-profile aluminum strut channels, 6ft long. Our 2005 Sprinter has no OEM mounting points, so we used three M8 rivnuts per channel, drilled with a step bit.
Installing rivnuts without a special tool: thread a long bolt (matching the rivnut's pitch) through a couple of nuts larger than the bolt and some washers, insert the assembly into the hole, and tighten the bolt with an impact drill while holding the nuts steady with a wrench. Tighten gradually until you feel the rivnut compress, then loosen the bolt. The rivnut stays in place. Don't over-tighten, or you risk stripping the knurls.
Solar panel mounting brackets
Using 1.25" angle aluminum, we cut four 2ft pieces for the short sides of the panels, made slotted mounting holes on one leg for adjustability, and drilled rivet holes on the other leg to attach to the panels. We centered the brackets, transferred the hole locations to the panels, drilled through, and set the rivets with a rivet tool.
Roof preparation and rail installation
Before finishing the install, we addressed surface rust along the body seams and some scratched paint, using a wire wheel to remove rust and a coat of rust inhibitor. We applied the same Bostik 70-03 sealant used on the fan along the seams, smoothed it out, and painted over it once cured. We slid channel nuts into the rails before tightening the mounting bolts, using large fender washers for clamping force and blue Loctite on the threads.
Final solar panel installation
With the rails attached, we placed the panels on top, aligning the slotted bracket holes with the channel nuts, and connected the two panels with a parallel wiring harness adapter. Since the mounting bolts were a little short, we used a magnet to hold the channel nuts up high enough to catch a few threads, applied Loctite, and torqued everything down with an impact driver (around 30 ft-lbs with a torque wrench, if you want to be precise).
Cable gland installation
We placed the cable gland between the two panels, cut with a 1.25" hole saw and cleaned up with a file and paint on the raw edges. MC4 connectors on 12-gauge wire connected to the parallel harness, fed through the gland, and sealed with DAP silicone and self-tapping screws.
Conclusion
The installation was a success, and several long highway trips have proven everything is mounted secure and safe. We'll cover the full electrical setup in a future write-up.