Sprinter Adventure Van Build – Heater Install

Honestly I think installing the heater was the hardest thing we have done in the fan so far. It’s not particularly difficult, but there are a lot of parts and pieces, do’s and don’ts, and in’s and out’s (inside and outside work, that is).

Summary (TL:DR):

Purchased the Eberspacher/Espar D2 heater kit from www.heatso.com which is a company based in the UK. It shipped super fast and even with the import tax was still way cheaper than any deals we could find here. The install package came complete with everything we needed to install except for good instructions – which we put together from various posts and manuals found online. Installed the heater under the passenger seat. It works!

Custom Text


  • Drill
  • Large hole saw bits (2″ + i think)
  • hack saw or saws-all
  • soldering iron
  • grinder
  • wrenches, ratchets, screw drivers, etc.
  • patience


  • Espar/Eberspacher D2heater kit
  • A short (12”) piece of 5/16” black flexible fuel line
  • two hose clamps
  • metal male-male 1/4″ barbed connector
  • solder, heatshrink tubing, electrical tape, etc.
  • aluminum / heat reflective tape (same stuff we used on the reflectix) for use as a heat shield
  • rust inhibiting paint (for touch up)
  • butyl tape – for sealing around the mounting flange
  • zip ties
  • I have added the High Altitude Kit (after encountering some operations issues at altitude)



The references above are really good so given that, I am not going to go through my usual detailed process here. I will highlight some of the specific things that we did.

Fittings that come with the heatso espar d2 kit
Fittings that come with the heatso espar d2 kit

The install kit that came with our heater really had everything we needed for the install, save fore the items listed above. All kinds of good fittings for various install options. There were a few barbed tee fittings which I guess are used for if you are cutting into an existing accessory fuel line (like if you have the factory oem espar installed under the hood). Since we didn’t need to do that, we didn’t use several of the pieces, but it was nice to know we had them.

When I first opened the box I freaked out – OMG there are a lot of things in here. But when you break it down it really isn’t that complicated (really). On the heater you have:

  • Combustion air inlet (intake, 25mm)
  • Combustion air outlet (exhaust, 24mm – smaller!)
  • fuel intake
  • power wire loom (with a few wires in it)
  • control wire loom (with a whole bunch more wires in it – but you don’t need most of them!)

We decided we wanted to put our heater under the passenger seat. This was mostly because we have no idea how we are going to ‘finish’ the rest of our van, in terms of furniture, cabinetry, tables, and the like – so putting it under the passenger seat seamed like a good “no consequence” place to start cutting more holes in the van. We were pretty sure with it under there that we wouldn’t be tripping over it in the future.

So the front passenger seat came out. Since we have heated seats and those side airbags there were a few electrical cables to undo. These were easy enough to detach at their connectors but be warned: I am told that if you start the vehicle with these cables detached you will get a persistent fault (even after you reattach them) regarding the ABS system. This is easy to reset/clear at the dealer I guess, but I didn’t want to risk it. I didn’t test out if this warning is true. I just made sure to connect the seat back in before starting the vehicle (or even putting the key in the ignition). Maybe others will be bolder and can tell me I’m wrong – that’s fine.

Installation bracket
Espar D2 Heater Installation bracket

We ordered the heater with this nice installation bracket. When it came, I had no idea how it was supposed to work. It also came with this nice rubber gasket. Since I forgot to take a nice picture of the gasket and how all of this stuff was (maybe) supposed to go together, I built a 3D model instead.

So how does that work? See the model below…
Left side: the gasket appears to be perfect for the bottom of the heater, but if you put it on the bottom of the heater, how does it fit into the cylinder portion of the mounting bracket?
Right side: Am I really supposed to cut a 5″ hole in the bottom of the van for the “cylinder” of the mounting bracket to fit in? Doesn’t leave a lot of sealing surface between the van floor and the flange.fan mount question

After staring at the heater, the gasket and the mounting flange for about three hours I decided there was no hope and I couldn’t figure out how to make the three of them work together. I probably could have emailed and/or called heatso and they would have helped me (sprintervandiaries says they were very helpful) but I didn’t do that – I guess I tend to stress the Y in DIY. Anyway – after careful deliberation, I decided to take matters into my own hands and ‘customize’ the mounting bracket. I cut the cylinder portion of the mounting bracket of with the grinder. It was just 4 welds and went pretty fast.


This is the setup I went with ultimately. Without the cylinder attached to the flange I had a nice flat mounting surface to place the gasket on and a nice flat surface to mount against the van floor. I used butyl tape to seal between the mounting flange and the floor of the van (yes! the same tape we used for mounting the fan on the roof!!). The layup order is (from outside to inside):

  1. van floor
  2. butyl tape
  3. mounting flange
  4. rubber gasket
  5. heater
heater bolted up
All bolted up (virtually)

The mounting flange also served as a great template for drilling the holes. And because the flange was sealed against the floor of the van, I could oversize the holes in the floor of the van (for some wiggle room) and not worry at all about having a leak. Bolts in the bottom of the fan and bolts in the mounting flange all went through the van floor with washers and nuts on the other side (outside of the van) to hold everything nice and snug together. Ultimately I have to say this worked out very nicely.

espar - easy start wiring annotation

The second hard part was wiring the controller. We ordered our heater with the “easy start timer”. The kit came with an install CD and while the wiring instructions were plentiful, they weren’t exactly straightforward – well at least not to me. Actually, now looking back they are very straightforward – I was just so thrown off that there were a bazillion wires coming off of the easy start timer module and a whole bunch coming from the heater, but you only connect to 3 of the wires from the espar wire loom and connect to wires from the espar together. Really, that is it. I have annotated the wiring diagram for your (and my) reference.


Wiring of the main heater itself is pretty straightforward. You have three main wire looms: (1) the control unit wiring bundle. (2) the power wiring bundle (with the red wires). (3) the fuel pump power/ground bundle. Its pretty straightforward which one is which. And I have annotated another diagram, for reference.

BIG NOTE: we did not get the high altitude adapter and thus have no reference to wiring for that. sorry. I have since added the high altitude kit after having some heater issues when camped at altitude. Information on the high altitude kit install can be found here.

For the rest of the details, I am going to go ahead and say check out the references. especially this one from sprintervandiaries. because its very detailed.

I mounted the fuel pump inside the aluminum protector that covers the main sprinter diesel fill line. I liked the idea that it would be protected from debris getting kicked up from the road. However, the routing of the intake hose from the OEM auxilliary fuel pick-up was a little tricky (it does a u-turn into the fuel pump) and may not be the best routing. it seems to work for now. To do it, I just pulled of the aluminum protector, drilled a hole in it at the “right” spot and then bolted the pump to it.

A few more photos, just for your reference:

On the close up, you can see its a tight squeeze between the sprinter fuel filling pipe, the fuel pump, and the OEM auxiliary fuel pick-up line going the other direction. You can also see the hose clamp over the 5/16″ rubber hose. As mentioned in the sprintervandiaries post – it was really quite difficult to get the 5/16″ hose over the factory fitting. but using a heat gun helped.

Because or heater was installed on the opposite side of the van as the fuel tap, we routed the fuel line across the vehicle, using lots and lots of zip ties as well as ‘heat shielding’ the fuel line with the reflectix tape where it crossed the exhaust and other ‘hot’ parts.

That pretty much covers this installation.

9 thoughts on “Sprinter Adventure Van Build – Heater Install

  • Thanks for the advice on prior installs. Now thinking about a heater. Question about your through-floor holes: you used butyl on the top flange, so that keeps water from getting into the vehicle. Did you use any sealant for bottom of the holes? Any concerns about water getting up and trapped under the heater flange? Or are the pipes through the holes so snug it isn’t a concern?

  • John

    Did you power your heater directly to the battery next to it? With an inline fuse? Or run the wires to your fusebox, then back to the heater?

  • I’m about to tackle a heater install now that the weather is a bit better. Thanks for the great writeup!

  • Thanks for the post. I put a D2 in my Sprinter, and because I was trying to maximize available space I got overzealous and boxed it into a cabinet with little space around it. I left openings in the back of the two sides that encase it, so that fresh air could reach the back, but unfortunately the D2 turns off after 15 minutes of running and displays an overheating warning, so I’m going to need to figure out how to vent it better. I am now remodeling a Sprinter for someone else and will be installing a D2 again. I am strongly considering putting it under either the driver or passenger seat like you did—seems like a great, out of the way place, but I was worried about the potential for the same overheating problem. You haven’t had that issue? I am planning on adding a seat swivel which will enclose the space even more.

    • Austin

      Tad, sorry to hear of your troubles with the heater. I have not experienced overheating issues. The passenger seat does have a panel on the door side that I have cut several slits in to allow even more air to enter into the heater area. I am not sure if this is absolutely necessary, but it seemed to make sense at the time.

      Espar recommends certain clearances around the heater, I don’t know what they are off-hand, but if you are worried about it I would probably try and maintain those. It seems lots of people have installed their heaters under the passenger seat and I haven’t heard of too many issues. But you might try searching on the forums and query others with this issue. I am certainly curious what you might find.

      I have been having some heater troubles this winter myself – but these have been diagnosed as fuel/burn balance related and I think caused by being at altitude. I am hopeful that installing the high altitude kit will fix the issue. I’ll have a write-up on the high-altitude kit install soon.

  • Bill G

    Love the info. very helpful! My fiance and I are trying to install our heater kit and have a question in regards to the wiring. We just have the Easy start select and not the timer. in your information you say that you connect the three wires (Red, Brown, and Blue/white) to the controller and then connect two together. Do I connect still just connect the gray/red and brown/white wires together without the timer? I was just wondering if you could help. thanks and again your information was super helpful.

    • Austin

      Bill – thanks for the comment. I am far from an expert on the wiring of the espar heater. I just posted what worked for us and my interpretation of the installation manual. Speaking of manual – attached here is the manual that came on the CD with our kit (hope its okay to post here) (Download).

      Looking at page 39 of that booklet it appears that the wiring is the same for the easy start timer as for the easy start select. We are on the road so I didn’t take a long look – I highly recommend confirming for yourself. However, based on my quick look it appears that, yes – the two wires should still be connected together.

      Best of luck with your install. With winter underway here in the PNW we have been using our heater a bunch lately. Its wonderful to come back to the van after a wet day skiing and have it already warm and cozy inside.

  • What size battery were you able to fit under your passenger seat alongside the D2?

    • Austin

      We put a 100 amp hour batter next to the heater and strapped it to the side of the seat so it doesn’t accidentally slide into the heater when cornering. More info on that and the rest of the electrical build here: Sprinter van Electrical


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