My Ford Transit Under-Seat Diesel Heater Build

I installed a maXpeedingrods diesel heater beneath the front passenger seat of my 2023 Ford Transit 250 High Roof Extended. The project stretched across four build-diary entries, from March 29 to April 3, 2024. Along the way, I cut the floor opening, mounted the underbody components, built a custom vent cover, and worked through awkward screw angles and trim that would not stay attached.

The custom cover became a project of its own. The back of the passenger-seat platform slopes toward the floor, and I wanted the warm-air outlet to face straight into the van. Making that happen meant shaping a black aluminum composite panel, adding triangular sides, and finding a way to attach it in a cramped space.

My Heater Build At A Glance

Day 88: Opening The Floor

On Day 88, I removed the passenger seat and set it aside to expose the seat base and floor. I cut away the plastic flooring at the heater location, then used the mounting plate and a marker to lay out the opening.

I started the cut with a drill and step bit, then worked through the opening with a reciprocating saw and grinder. Two DEWALT metal-cutting reciprocating-saw blades broke during this part of the job. Getting the opening cut took several tools rather than one clean pass.

Once the opening was made, I sanded the surrounding area and applied two coats each of primer and paint. I attached the heater's intake, exhaust and fuel tubing, guided them through the floor, and set the heater in position for the next day's work.

Day 89: Working Underneath The Van

Day 89 was mostly spent on my back beneath the van. I mounted the intake and filter, exhaust tubing, fuel filter and fuel pump, working with the kit's clamps and hardware along with metal zip ties from my own supplies.

This was the most physically draining part of the project. Without a lift, I had to hold my head up to see the work while reaching into the tight space under the van. My neck, upper body and abdominal muscles all felt it. Two of my four vehicle ramps were also destroyed that day after previously starting to crack.

Back inside, I worked on the passenger-seat platform to make room for the vent and cover. Cutting and filing the platform added another fabrication task before I could move on to the finished panel.

The black coating visible in the underbody photographs is Fluid Film Black, which I had applied to the undercarriage apart from the exhaust parts.

Day 90: Making The Custom Vent Cover

On Day 90, I focused on the warm-air duct and the panel behind the passenger seat. I wanted the vent at a right angle to the van floor instead of following the slope of the seat platform.

I already had black aluminum composite panel from Amazon because I had considered it for the van's interior paneling. I found it easy to cut and work with, and I liked its appearance. I measured and cut the front panel, then made two triangular side pieces to close the gaps beside it.

I joined the pieces with metal brackets and self-tapping screws. Attaching the cover to the sloping seat platform was more awkward: the screw angle was difficult, and I made an unwanted hole in the panel. My plan was to cover that spot with a larger washer.

I shortened the warm-air tubing to reach from the heater to the vent in the cover. I also started moving the red, black and LCD-panel wires beneath the plastic flooring toward the passenger-side pillar area for later routing to the rear of the van.

Day 93: Trim And Fuel-Pump Wiring

By Day 93, I was finishing the cover edges and working on the fuel-pump wiring. I ran the pump wires through a factory floor opening and its rubber gasket, then applied sealant around the wire passage.

The L-shaped black trim was supposed to finish the panel edges, but its adhesive did not want to stick. I used super glue to hold it down and blue painter's tape to keep it in place while it bonded. The tape in the photograph is part of that finishing process.

I marked the heater project completed in that day's diary. My remaining wiring task was to run the red, black and LCD-screen wires toward the back of the van together with the other wiring. Solar panels and the roof vent fan were next on my project list.

What Stood Out From The Project

The hidden work took a large share of the effort. From inside the van, the heater sits in a compact space beneath the seat. Underneath, there were several separate components to position and mount, all while working in a cramped space.

The cover also took more work than simply cutting a flat panel. Its angle affected the outlet direction, the triangular sides, and how I could reach the attachment screws. Reusing material and brackets I already had helped me work through the design as I went.

The small finishing details were memorable too. Broken blades slowed the floor cut, an awkward fastener left a hole to cover, and the edge trim needed extra help to stay attached. Those are the details that filled the gap between placing the heater under the seat and getting the surrounding panelwork together.

Parts And Tools From My Build

Amazon disclosure: As an Amazon Associate I earn from qualifying purchases. The Amazon buttons below are paid links.

Follow The Rest Of My Build

The four original entries contain the step-by-step notes, additional photographs and videos: Day 88, Day 89, Day 90 and Day 93.

Browse Resources for more projects and tools, or explore how I planned the van with SketchUp.