Camper Van Conversion and Build Out in San Juan Capistrano

The three common conversion platforms are not interchangeable. A Sprinter gives the most interior height and the best long distance road manners, along with the most complex electrical architecture and the most expensive parts. A Transit offers a wide range of roof and wheelbase combinations and a far friendlier parts and service network. A ProMaster has the widest body relative to its footprint, which is the only platform where a bed fits crosswise for most people, and it is front wheel drive with a low load floor.

Those differences propagate through the entire build. Bed orientation decides the galley layout, which decides where the water system lives, which decides where weight sits relative to the rear axle. Getting the platform right for the layout you actually want is the single highest leverage decision in the project, and it happens before anyone touches a tool.

Wall geometry matters more than people expect. Sprinter ribs and ProMaster ribs are shaped completely differently, which changes how furring strips attach, how insulation packs and how flat a finished wall can be. A cabinet design that works on one platform has to be redrawn for another rather than adapted with shims.

A van is a steel box with a large surface area and no thermal break anywhere. Every rib and every fastener that touches the outer skin conducts heat, and in a cold night that means condensation forms on the coldest interior surfaces, which are exactly the metal ribs behind your finished wall. Water that condenses inside a wall cavity does not evaporate quickly, and rust follows.

The approach that works is to insulate the cavities, break the thermal bridge at the ribs with a layer that separates furring from steel, and treat every bare metal surface with a coating before it is covered. Wool-type insulation such as Thinsulate handles the moisture cycle well because it does not hold water against the steel, and closed cell foam in the right places seals cavities that cannot be reached later. Fiberglass batt from a home improvement store is the wrong material for a vehicle and we will not fit it.

Ventilation completes the picture. Two humans breathing overnight produce a surprising volume of water vapour, and cooking adds to it. A roof fan that can both exhaust and intake, combined with a window or vent that provides makeup air, moves that moisture out of the vehicle before it condenses. A perfectly insulated van with no ventilation is a damp van.

Every van has a gross vehicle weight rating and a payload figure that is smaller than owners expect once fuel, passengers and gear are counted. A build that ignores this produces a vehicle that is overloaded on its rear axle, handles badly, wears tires unevenly and is technically illegal on the road. It also voids nothing on the insurance side until there is a claim, at which point overload becomes a very inconvenient conversation.

So we run a weight budget from the first drawing. Every major component gets an estimated weight and a position, water tanks in particular because water is heavy and it moves. A thirty gallon fresh tank is a substantial mass and where it sits relative to the rear axle changes the handling of the vehicle meaningfully. We weigh the finished vehicle by axle rather than trusting the arithmetic.

The tradeoffs get made openly. A large water capacity, a big battery bank, solid wood cabinetry and a full wet bath will not all fit inside the payload of a typical van, and choosing among them is the owner's decision to make with real numbers in front of them. That conversation is much better before the build than after.

A conversion electrical system is designed as a whole: battery bank sized to measured consumption, a solar array, a DC-to-DC charger drawing from the alternator, an inverter-charger for shore power and household outlets, a fused distribution panel and a shunt-based monitor. Every conductor is sized for its load and its length, and every circuit is fused at its source. The wiring diagram exists on paper before any cable is pulled.

Chassis integration is where conversions get into trouble. Modern vans manage their electrical systems over a data network, and tapping into circuits at random confuses body control modules and produces faults that appear nowhere near the modification. Sprinters in particular have documented upfitter connection points for exactly this reason, and using them is not optional if you want the vehicle to behave afterward.

The alternator deserves specific mention. A lithium house bank will accept everything an alternator can produce for as long as it is offered, and a smart alternator on a modern van was not designed to deliver that continuously. A DC-to-DC charger limits the draw to something the alternator can sustain and provides the correct charge profile at the same time. Wiring a lithium bank directly to the starting system is how people cook alternators.

Van water systems are compact versions of RV systems with the same physics. A fresh tank, a demand pump, an accumulator, PEX runs supported and protected, a water heater or an on-demand unit, and a gray tank that must be somewhere. Freeze protection is a real design question even for a California-based van, because the vehicle will go to elevation and exposed underbody tanks and lines freeze first.

Diesel air heaters have largely won the heating argument in vans. They draw a fraction of the electrical power of a forced air LP furnace, they burn fuel from the vehicle tank so there is no bottle to manage, and they modulate output smoothly. Installation quality decides whether they are reliable: exhaust routing away from any opening, correct fuel pump mounting angle, and a fuel pickup arrangement that cannot draw the vehicle tank down below driving range.

The wet bath question comes down to how the van is used. A full wet bath consumes a meaningful share of a van's floor area and its payload, and for many owners a cassette toilet with an outdoor shower delivers most of the practical benefit for a fraction of both. For full-timers and anyone travelling in weather, the wet bath earns its space. We ask the usage questions before drawing the layout rather than after.

Not every project is a bare van. A significant share of our conversion work is finishing or correcting builds that started somewhere else: an owner who ran out of time, a build from a shop that no longer exists, or a self-build that got as far as the electrical system and stalled. We are happy to take those on, with one condition, which is that we open up enough of the existing work to know what we are building on top of.

The most common thing we find is wiring that will not pass any reasonable standard: unfused runs, undersized conductor, wire nuts, automotive-grade untinned wire in a damp environment, and a lithium bank connected to a charge source with the wrong profile. Correcting those is not optional if we are putting our name on the finished vehicle, and we price it honestly rather than building over the top of it.

The second most common is water intrusion around a roof fan or a window somebody fitted without proper sealing technique. Those need to be pulled, the opening properly prepared and the unit reset, along with repairing whatever the leak has already damaged. Finding it at the start of a build is inconvenient. Finding it after the walls are closed is far worse.