Installing a caravan diesel heater safely means sealing every floor opening, venting intake and exhaust outside, and wiring it on a fused 12V feed.
For the full breakdown, see our best Diesel Heater guide.
The installs that fail usually fail the same three ways: combustion air drawn from inside the van, an unsealed floor cut, or a 12V feed that sags under load. Get those three right and the rest is patient, methodical work — whether you are learning how to install a diesel heater in a caravan, a campervan, or a small motorhome.
The job runs in four phases: choose a mount spot and cut the floor, route intake, exhaust, and fuel, wire a fused 12V supply, then test everything with a carbon monoxide alarm in place. If you have not picked a kit yet, our tested picks for the best diesel heaters compare complete packages before you make the first cut.
Installing A Diesel Heater In A Caravan: The Step Order That Works
The reliable order is mount and floor first, air and fuel second, wiring third, and testing last. Changing that order usually means taking something apart to redo it.
Choose a spot under a dinette seat, under a bed, or inside a protected cabinet or seat box. You need clearance around the heater body for ducting, the exhaust run, and future maintenance, and the mounting surface has to be flat and smooth so the plate can seal completely against the floor.
Then the floor work follows one pattern. Cut the openings for the heater mount, the exhaust, and the intake. Run silicone or sealant around every cut and underneath the mounting plate, then bolt the plate down. Finish by cutting and fitting the interior hot-air outlet ducting, keeping the intake and outlet routes separate as the kit’s instructions show.
Intake, Exhaust, And Fuel: Route Each Line Outside
The exhaust pipe has to discharge outside the caravan, and the combustion intake has to draw from outside as well. Neither opening belongs under the floor, inside a skirt, in a wheel well, or in a sealed locker, because fumes from those spots find their way back into the living space.
Make the exhaust outlet clear the bodywork and slope the pipe slightly downward so condensation drains instead of pooling. Set the intake on the same side of the van, at least 200 mm (about 8 in) from the exhaust opening, and use heat shielding anywhere the exhaust passes close to bodywork or heat-sensitive materials.
The venting rules above follow Born to Roam’s diesel heater installation manual, which walks through the same order: sealed floor openings first, then intake and exhaust routed outside before any wiring begins.
The fuel side is simpler. Mount the metering pump close to the tank and isolate it with rubber so the normal ticking does not drum through the floor. Run the fuel line without kinks, secure it with proper clamps and fittings, and seal every exhaust joint — loose couplers and unsealed joints are a leading cause of fumes reaching the cabin.
What 12V Wiring Does The Install Need?
Every diesel heater install needs one dedicated fused 12V feed from the leisure battery or the 12V distribution bus, a controller wired in, and a carbon monoxide alarm tested before the first night’s sleep.
These heaters draw heavily during start-up, and a thin or shared supply creates voltage drop. Poor voltage is one of the most common causes of failed starts and lockouts, so run the fused feed straight from the leisure battery and keep every connection clean and tight. Most kits use a wired LCD controller; guide its wiring to a dry, reachable spot and mount the panel there.
Most installs that end badly involve the same handful of mistakes:
| Common Mistake | The Result |
|---|---|
| Combustion intake pulling air from inside the van | The heater burns the cabin’s oxygen and can draw in its own exhaust |
| Intake and exhaust set too close together | Exhaust gets sucked straight back into the combustion air |
| Exhaust outlet ending under the floor or in a wheel well | Carbon monoxide recirculates into the living space |
| Exhaust joints left unsealed | Hot fumes leak into the van and reach the cabin |
| Thin or unfused 12V wiring | Voltage drop produces failed starts and lockouts |
The first-run test is the last step. Run the heater on high, put your hand around every exhaust joint and the floor seal, and check for the smell of exhaust anywhere in the van. Confirm both ducts deliver airflow, then check everything again once the heater is hot. It passes when there are no leaks, no fumes, and a steady flame — that is when the install is done.
FAQs
Where Do Most Caravan Diesel Heaters Get Installed?
Most go under a dinette seat, under a bed, or inside a protected cabinet or seat box where they stay out of the way. The spot still needs clearance around the heater body for ducting, the exhaust run, and maintenance access, and the floor surface beneath it must be flat, smooth, and easy to seal completely.
Is Sleeping With A Diesel Heater Running Safe?
Yes, when the install is correct and the safety checks are done. The intake and exhaust must both reach outside, every floor opening and exhaust joint must be sealed, and a listed UL 2034 carbon monoxide alarm has to be fitted and tested before you sleep. Never rely on the heater with an exhaust leak or an indoor combustion air intake.
Why Does A Diesel Heater Shut Down Or Lock Out?
The most common cause is a 12V supply that sags under load. Diesel heaters draw heavily at start-up, so a thin wire, a poor connection, or a shared