Sprinter Van Conversion Rough Wiring
Updated: Jan 23
In this post we'll cover the rough wiring phase of our Sprinter Campervan Conversion. It is handy (and fairly necessary!) to do some wiring prior to installing wall panels, cabinets, and other major components of the build. This is a basic guide to the rough wiring we did in the initial phase of our build. We'll be posting a thorough rundown of our entire electrical system in the future and will update that here with a link when it is live.
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We should also say that we are not electricians. Cade has spent a lot of time reading up on wiring and solar electrical systems (thanks internet!), and did a great job of building a solid electrical system in our van. However, this is by no means a complete DIY guide. If you don’t have electrical experience, you may want to consult with an electrician to help you with your conversion. Especially if you plan to use solar panels, someone who is knowledgeable about solar electric systems can make this process way more straightforward for you if you're totally overwhelmed. If you do plan on figuring it on your own, please realize that we are not experts by any means and this post will only serve as a guide for someone who already has a basic understanding of electrical systems. Even after lots of research, we learned some wiring lessons the hard way during our first Sprinter Van conversion, but we do feel that we have greatly improved our electrical system in our second van.
The first step to rough wiring is to have a plan for what electrical components you want in your van and where they’ll be. It can be hard to have all those things figured out this early in your build, but if you’ve got a solid wiring diagram and a plan in place before you start building stuff, it will make life much easier later on.
As you'll notice in the photos, we were more or less simultaneously installing our insulation as we did this phase of wiring, which worked out pretty well (they occupy many of the same spaces and it will become obvious as you go where wires need to go on top or underneath insulation and how they work around each other). Once you've got these wires in place, they will be left dangling until you get the various components installed. It's a great idea to label each wire so you remember what's what down the line when you are ready to start hooking everything up and you've got walls installed and things become a lot less obvious. We used painter's tape and a sharpie to label each wire as we went.
For our system we planned to house the batteries and most components in a box under the bed (in the back of the van above the passenger side wheel well), so this electrical box is where most of our wiring runs begin. These runs then branch out into three main parts: the 12V DC loads, the 120V AC loads, and the solar charging system.
We ran all the wires behind the steel framing of the van wherever possible to guard the wires. We also protected the wires using a combination of braided abrasion-resistant wire guard, split wire loom, and heat shrink wherever there was any chance of rubbing or abrasion.
For AC wire, we used a heavy-duty braided copper extension cord. For the DC wiring, we used marine-grade covered duplex wire (mostly 16awg) because we made it a “floating” system with no chassis ground. We’ll be discussing this topic in more detail in the electrical system post.
Solar charging system and light bar
Our one short and two long solar panels are run in a series, so there are only two wires that pass through the roof of the van from the panels. Once inside the van, the solar wires run rearward along the ceiling of the van and then down the passenger side wall to the electrical box above the wheel well. We also added a light bar, which is attached to the roof rack in front of the short solar panel. The light bar has its own separate wires that come down through the roof as well. Once inside the van, the light bar wires are routed down the driver side B Pillar to connect to the vehicle battery under the driver seat. We used three cable entry elbows to pass the wires through from the roof to the interior of the van.
12V DC System
The majority of our electric components in the van run off of DC Power. We’ll be covering this more thoroughly in a future post, but our lights, 12V outlets (what you probably know as ‘cigarette lighters’), our refrigerator, our Webasto heater, water pumps, roof fan and our propane/CO alarm are all run off of DC power. Especially if you're considering using solar power in your conversion, this is a topic you're definitely going to need to dive into and learn about.
Our 12V loads are divided into two fuse blocks; one is housed inside the electronics box above the passenger-side rear wheel well. This fuse box distributes wires to the overhead lights, 'storage' lights (under the bed) and ceiling fan (these wires run up the wall and into the ceiling), our Webasto Heater (these wires run forward under the sliding door footwell to the passenger seat pedestal where the heater lives), a 12v outlet next to the head of the bed, our propane/CO2 alarm, and fridge (these last three wires run towards the front of the van towards their future homes). The ceiling fan is probably going to be one of the first components of the electrical system you install, and potentially one of the first projects you do on your van. This post covers the installation of our roof fan.
The other fuse block sits under the bed frame on the driver side of the van. We ran 6 awg wire from the electrical box across the van under the bed framing for this fuse block. This driver-side fuse block distributes wires to our two water pumps (one pump is housed right next to the fuse block under the sink; the other pump is under the van, so wires run out through the floor), kitchen lights (wire goes up the wall), and two 12v outlets--one on the kitchen wall and the other by the head of the bed on the driver’s side (these wires run up the wall and foreward/back towards their future homes).
120V AC System
Because the majority of our electrical components run on 12V DC, the 120V AC system is quite simple in our conversion. These are what you think of as a standard ‘wall’ outlet in a house. We just have two of these AC outlets in the van. One outlet is in the storage area wall panel under the bed on the passenger side. This was a short run because it sits just behind the electrical box on the passenger side. The second outlet is on the kitchen wall, just behind the driver’s seat. The wire for this second outlet runs from the first outlet forward, across the van under the bed frame and along the driver side wall.
Factory Vehicle Wiring
One last thing we decided to do while rough wiring was to re-route the factory wire loom that runs along the corner of the ceiling and driver’s side wall back to the tail lights and other components in the back of the van. When Sprinter vans come from the factory, this wire loom runs below all the roof cross-members. In our first Sprinter van it was a constant headache trying to build cabinets and trim around this thick wire loom, so we decided to relocate it behind the cross-members of the van framing and out of the way.
This job requires cutting and splicing each wire, and there is a bit of a pinch point in the middle where the C pillar is, but we found that there is enough room to get all the wires through. There are 10 or 15 wires total. Once Cade had clipped all the wires, he realized one of them looked different than the rest, and had a moment of panic… oops! Upon close inspection he discovered that they are not all power wires. The odd one turned out to be the coaxial cable for our backup camera. After a bit of googling and a Youtube video or two, Cade’s brother came to the rescue and helped splice it back together with some tin foil and multiple heatsink layers. Just like new!
We are happy to report that after over a year in the van, we have not had any issues with our electrical system and that we made far fewer wiring mistakes in our second conversion.... so at least we know that we are learning as we go! We hope this post has been helpful as you plan the wiring for your campervan conversion.
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