A used Class B camper van is the trickiest RV to buy well, because you're really buying two things at once. Underneath is a commercial cargo van — a Ford Transit, Ram ProMaster, or Mercedes Sprinter — with an engine, transmission, and a service history that has nothing to do with camping. Bolted into that shell is a "house": a conversion built by a factory like Winnebago or Pleasure-Way, or by a small shop, or by the last owner in their driveway with a YouTube tab open. A gorgeous kitchen means nothing if the diesel needs a new turbo, and a bulletproof drivetrain means nothing if water has been quietly rotting the floor under the bed for two winters. Your job is to inspect both halves and, more importantly, to judge the balance between them. A 140,000-mile Sprinter with a flawless professional build can be a smarter buy than a 40,000-mile van someone gutted and re-plumbed with hardware-store parts. Below is how to read the chassis, the house, and the seams where water sneaks in — and how to weigh them against each other before you sign.
Start Under the Van: Gas vs Diesel and the Miles That Matter
The chassis is the expensive part to fix, so read it first. Class B vans ride on three common platforms: the gas Ford Transit and Ram ProMaster, and the diesel (and some gas) Mercedes Sprinter. A gas van is cheaper to buy and to repair, and almost any shop can work on it. A diesel Sprinter gets better fuel economy and tows and climbs better fully loaded, but the maintenance is specialist work — emissions components (DEF system, EGR, DPF regeneration) fail expensively, and a shop that knows them can be a long drive away. Neither is 'better'; match it to how you'll actually use the van and how far you live from a competent mechanic.
On miles, judge them by how the van lived, not just the odometer. A camper van that spent 90,000 miles on highway road trips is gentler service than a former cargo van that idled all day making city deliveries. Ask for the full service history and look for a real paper trail of oil changes; diesels are unforgiving of neglected oil and fuel filters. Cold-start the engine yourself — never let the seller warm it up before you arrive — and watch the exhaust for blue (oil) or persistent white (coolant) smoke.
- Green flag: documented oil-change history, a transmission that shifts smoothly without flare or clunk, and steady oil pressure and temperature on a longer test drive that includes highway speed.
- Red flag: a diesel with a check-engine light, an active DEF or 'limp mode' warning, or an owner who volunteers that a regen 'sometimes acts up' — that's an expensive emissions repair waiting to happen, not a quirk you can ignore.
- Ask exactly when the timing components, glow plugs (diesel), and transmission fluid were last serviced, and get the mileage those were done at, not just the date.
- Have an independent mechanic who knows that specific platform do a pre-purchase inspection with a scan tool — the reading of stored fault codes alone is worth the fee.
Hunt for Water Intrusion — It's the Silent Van Killer
Water damage destroys more camper vans than engines do, and it hides. Every hole cut into a van's roof and walls — the pop-top canvas seam, the roof vent, the solar-panel mounts, the fridge vent, and every window — is a place sealant can crack and let rain in. On vans with a pop-top or penthouse roof, the fabric bellows and its mounting rail are the number-one leak point; work the top up and down and inspect the canvas for mildew, stiff patches, and stitching that's pulling away.
You're looking for the aftermath as much as the source. Bring a cheap moisture meter, or at minimum your hands and nose. Press on the ceiling panels, the walls near windows, and the floor around the bed and under the fridge — anything soft, spongy, or stained is rot. A musty smell that hits you when you first open a closed-up van is a warning that no air freshener can cover.
- Inspection checklist: press every ceiling and wall panel for softness, especially around the roof vent, any pop-top rail, and the top corners of every window.
- Peel back the mattress and any bed cushions and look at the platform and floor underneath — this low, hidden spot is where leaks pool and rot starts unseen.
- Open every cabinet and run your fingers along the back walls and lower corners for water stains, bubbled veneer, or a damp feel.
- Look at the sealant beads around the roof vent, solar mounts, and windows: fresh, mismatched caulk can mean a recent leak was covered up rather than properly fixed.
- Red flag: rusty screw heads bleeding down an interior wall, warped or delaminating paneling, or a seller who's clearly run a dehumidifier and cracked the windows right before you arrived.
The House Electrical: Batteries, Solar, and the Inverter
The 'house' 12-volt system is the heart of a modern camper van and the most common place a driveway build goes wrong. Find out what the house battery actually is: an old flooded or AGM lead-acid bank has a short life and may already be tired, while lithium (LiFePO4) holds up far better but should come with a battery monitor showing its health. Turn everything on at once — lights, fridge, water pump, fan — and watch the battery voltage on the monitor; a bank that sags hard under light load is near the end.
Look at the work, not just the gear. Quality builds have fused circuits, properly sized wire, and a tidy panel; sketchy ones have wire nuts, undersized cable, and a rat's nest behind a panel that gets warm. If there's solar and an inverter, confirm they actually function: check that the solar is putting amps into the battery in daylight via the charge controller, and plug a real load (a laptop charger, a small appliance) into the inverter to confirm it holds up. Also confirm shore power works — plug the van into a household outlet with the supplied adapter and verify the converter charges the battery and the outlets go live.
- Green flag: a labeled fuse panel, a battery monitor (Victron or similar) you can read state-of-charge and history from, and a build that documents the wire gauges and fuse sizes used.
- Red flag: exposed or wire-nutted connections, a scorch mark or warm smell at the panel, or an inverter and solar setup the owner 'never really got working.'
- Ask the age of the house battery bank and whether lithium came with a low-temperature cutoff — charging lithium below freezing without protection ruins it.
- Confirm all three charging sources work: solar in the sun, shore power at the outlet, and the alternator/DC-DC charger while the engine runs.
Plumbing, Fresh and Gray Tanks, and Winterizing
The plumbing is simple but the failures are messy. There's a fresh-water tank, a pump, a faucet or two, and a gray tank for the drain water; some vans add a small cassette or portable toilet rather than a black tank. Fill the fresh tank, run the pump, and let water flow at every tap for a few minutes while you look underneath for drips at the tank, the pump, and every fitting. Then let the gray tank fill and drain it to confirm the valve and dump plumbing actually work and don't weep.
The bigger money question is freeze damage. A van that lived anywhere with winter and wasn't drained and winterized can have cracked pump housings, split tanks, or burst lines that only reveal themselves under pressure. Ask directly how it was stored each winter, and treat 'it never really got cold' with healthy skepticism unless the title history backs it up.
- Inspection checklist: run the pump with the fresh tank full and watch it cycle — it should build pressure and shut off, not run continuously (a sign of a leak or air in the lines).
- Fill and dump the gray tank to test the valve, and sniff for a sewer smell that points to a bad seal or a vent problem.
- Look under the van and inside cabinets for water stains or mineral crust around fittings — dried white residue marks a slow leak's path.
- Ask whether the water heater (if fitted) and lines were blown out or filled with RV antifreeze before winter storage every year it was owned.
The Galley: Fridge, Stove, and Heater
The appliances are what make a van livable, and they're worth cash to replace, so test each one cold. Camper vans use one of two fridge types: a 12-volt compressor fridge (like a Dometic or Isotherm) that runs off the house battery, or an older 3-way absorption fridge that also runs on propane. Turn the fridge on when you arrive and come back an hour later — it should be noticeably cold; a compressor fridge that never gets cold or runs constantly is a failing unit.
Light the stove and confirm each burner ignites and holds a clean blue flame. If the van has propane, the heater matters most for shoulder-season use: a diesel or gasoline air heater (Webasto or Espar) sips fuel from the main tank and is prized, but check that it lights without a smoky, sputtering start, which points to a clogged unit and a pricey rebuild. A propane furnace should light promptly and blow hot without a strong gas smell. Confirm the propane system holds pressure and, critically, that the van has a working propane/LP and carbon-monoxide detector.
- Green flag: a compressor fridge that pulls down cold within an hour, burners with steady blue flames, and a cabin heater that lights on the first try and runs steady.
- Red flag: a fridge that never gets cold, a heater that starts with black smoke or repeated failed ignitions, or a propane detector that's been disconnected.
- Ask the age and brand of the fridge and heater — a diesel air heater near the end of its life is an expensive repair or replacement, not a cheap part.
- Confirm the propane tank's certification date and that the regulator and lines show no corrosion or the tell-tale hiss of a leak (test fittings with soapy water).
Judging the Conversion Build Quality
Who built the van tells you a lot before you touch anything. A factory conversion (Winnebago, Pleasure-Way, Roadtrek, Coachmen and the like) is engineered, generally weighs within the van's rated limits, and has parts and manuals you can source. A reputable upfitter's build is often excellent and sometimes better than factory. A first-time DIY build is a coin flip: some are meticulous, many hide overloaded axles, ungoverned wiring, and cabinets screwed into thin sheet metal that rattle loose on rough roads.
Open and close everything and drive it on a bumpy road. Cabinet doors should latch and stay latched, drawers shouldn't fly open on braking, and the furniture shouldn't creak or shift. Ask to see the build documentation — a serious builder, pro or amateur, kept a wiring diagram, a plumbing layout, and receipts. Finally, check the weight: find the van's payload rating on the door-jamb sticker and be honest that a heavy build plus water, propane, gear, and passengers can push a small van over its limit, which stresses brakes, tires, and suspension.
- Green flag: solid, rattle-free cabinetry, accessible and labeled systems, and a builder (factory or individual) who hands over diagrams, manuals, and receipts.
- Red flag: furniture that shifts or creaks on a test drive, systems you can't get to without dismantling the van, and no documentation for how anything was wired or plumbed.
- Ask for the payload number and weigh the van's real-world loaded weight against it — an over-GVWR build is a safety and longevity problem, not a cosmetic one.
- Check that added weight sits low and balanced; a heavy solar-and-battery bank mounted high changes how the van handles in crosswinds and emergency maneuvers.
Balancing Chassis Miles Against House Condition
This is the decision that separates a good buy from a regret. Chassis problems and house problems cost very different amounts and are fixed in very different ways. A worn drivetrain is expensive and specialized; a tired house — old batteries, a dead fridge, sun-faded upholstery — is annoying but fixable in steps, often by you, for known amounts. So a higher-mileage van with a strong service record and a clean, dry, well-built interior can easily beat a low-mileage van whose house is water-damaged or wired badly, because rot and hidden electrical faults are the repairs that never quite end.
Price the van as the sum of two used items and their futures. Roughly tally what the chassis needs soon (tires, brakes, upcoming major service) and what the house needs (battery replacement, appliance age, any water repair), then negotiate from that number rather than the sticker. And because a van's true history — how it was stored, whether leaks were really fixed, whether the diesel was babied — is easy for a seller to gloss over, check the dealer's or seller's reputation the way you'd check the van: look for verified, proof-of-purchase reviews, and weight the ones written months after the sale that talk about how the van and any warranty held up.
- Rule of thumb: pay up for a dry, sound, well-documented house even at higher chassis miles — water damage and bad wiring are the repairs that compound.
- Be wary of a low-mileage van with a neglected or leaky interior; the number on the odometer is hiding the cost you'll actually pay.
- Build a two-column repair estimate — chassis soon-needs and house soon-needs — and bring it to the negotiation instead of arguing over the asking price.
- Pull the VIN and title history before you fall in love — a salvage or flood brand, or an odometer that doesn't match the service records, tells you what the seller won't.
The short version
- Inspect the van as two used vehicles: a commercial chassis and a bolted-in house, each priced and judged on its own.
- Cold-start the engine yourself and demand a real service history — a diesel Sprinter's emissions repairs and a neglected drivetrain are the costliest surprises.
- Hunt water intrusion hard: press panels around the pop-top, vents, and windows, and lift the mattress to check the hidden floor for rot.
- Power everything on at once and watch the battery monitor; test solar, shore power, and the inverter, and reject wire-nutted, unfused electrical work.
- Test every appliance cold — fridge, stove, and heater — and confirm working propane and carbon-monoxide detectors.
- Favor a dry, well-built, documented interior over a low odometer, and check the seller's proof-of-purchase reviews before you sign.