Once you’re done choosing the heater itself, now it’s time to decide where you want the heater to be. Depending on your cabin layout, as well as the size of your van, you can choose of the three locations:

• In the front, under the passenger seat
• In the center under the floor
• Near the back, if that’s where you spend most of your time
  

It’s very important to know for certain where you want your heater to be, as you will later need to measure out all the ducting, fuel lines, and wiring for your air heater.

The most common location to install a diesel heater in a van is under the passenger seat. This saves space, is relatively easy to access, and provides more options for how you want the heat to disperse.

For many, mapping out the fittings and adapters to install the heater and fuel pump is the hardest part. Knowing this in advance will help you plan ahead better and choose an ideal location for all your parts.

If you’re unsure how to do this, we suggest the most straightforward way: just crawl under your van and see what should go where and how much space you have to work with.

Arguably the most important aspect of your air conditioner is its cooling capacity. This is the measure of an air conditioning system's ability to remove heat from a room, thus making the room 'cooler'. As a rule of thumb, to calculate how much cooling you need, take the area of your cabin (width x height) and multiply that by 25 BTU.

Don’t forget that the bigger the cooling capacity of an AC, the higher its energy consumption. That’s why it’s always worth getting either exactly the cooling you need or a bit less. Otherwise, you may have to deal with an unexpected electricity bill.

Once you’ve decided where you want the heater to be, planned out the fittings, and installed the fuel line, it’s finally time to mount the air heater. If you purchase an Espar or Webasto air heater with an installation kit, it’s likely to include the mounting bracket, which will hold your heater in place.

To fasten the mounting bracket, we suggest forming some sort of insulated base. This can be anything, such as a block of plywood wrapped in foil or another form of heat insulation. This will prevent the heat from escaping the cabin, letting the heater do its job more effectively. Make sure your base has all the necessary holes for the cold air input, the fuel line, and the exhaust.

Before mounting the heater, be sure to first connect the intake, fuel line, and exhaust ducting. Once that’s done, feed the lines through your base, through the floor, to the underside of the van.

Now that the heater is mounted, you can run all the wiring from the control panel and fuel pump to your fuse panel. Wiring can be done discreetly, but it’s up to you to decide how and where you want your wires running. A general word of advice would be to keep the wires away from any moving parts and avoid sharp or hot surfaces.

When you have all the wires fitted and connected to your fuel pump and controller, like the Espar EasyStart Pro, you can test if everything is working correctly. Hook it up to your power supply – if everything was done right, the lights on the controller should turn on.

You’re almost finished! Congratulations, all the most difficult parts are now behind you. All that’s left now is to set up access to fresh air, a way for warm air to get in, and for the exhaust fumes to come out.

If you installed your air heater under the passenger seat, the most direct way to get hot air into the cabin is by drilling a vent in the seat’s base. With the heater mounted in place, measure as accurately as possible where the center of your hole will be. The better you do this step, the less heat you’ll lose, and your heater will work more efficiently.

If you’ve purchased a heater with an installation kit like the D2L Sprinter Kit, you’ll have the vent cover as well as the flexible tubing included. Plan where you’d like the heat to go, and install the hosing accordingly. Once complete, use the provided hose clamps to connect everything together.

The last step before starting the heater is to reliably fasten the intake and exhaust pipes under the van with the included hose clips. It is essential that you install the two hoses at least 3 feet apart, to avoid the intake hose sucking in the exhaust fumes and bringing them back into the cabin.