Espar S2 D2 Diesel Heater Install

Installing the Air Intake and Exhaust

Mounting the Fuel Pump

The Espar dosing pump draws fuel from the fuel tank and pumps it to the heater for combustion.  Accordingly, the next step in our install is to find a location under the chassis to mount the fuel dosing pump.  The fuel pump should be mounted as close to the source where the fuel will be tapped.  In the case of a Mercedes Sprinter, that is near the front of the fuel tank.  Espar requires the fuel pump be mounted at angle between 15 and 35 degrees to prevent formation of air bubbles in the fuel system.  Pay special attention to your specific manual as to the proper flow direction for your pump. This is important because the orientation of the newer S2 is the opposite of the older D2.  The pump can be mounted using a lag bolt or self-tapping screw.

Hooking up the Fuel System – Fuel Tank to the Espar Fuel Pump

The next step is to install the fuel system.  All U.S. NCV3 and VS30 diesel Sprinters have an auxiliary fuel tap that makes connecting a diesel heater very simple.  Some Canadian models lack the fuel tap, and I’m not sure gasoline Sprinters have one.  On the NCV3 (2007-2018) Sprinters the fuel tap is hanging near the front left corner of the tank.  On the VS30 (2019+) it is near a crossmember forward of the fuel tank.  

We will be changing tubing size several times–bear with us.  Remove the plastic rubber cap on the Mercedes Auxiliary fuel tap.  Next, click the Dorman adapter onto the fuel tap.  Use the short section of thicker fuel hose included in the kit and slide it over the barb of the Dorman adapter.  On the other end of the short fuel hose slide on the white adapter and secure both ends with the provided hose clamps.  On the other end of the white adapter, clamp on a short section of the medium-sized hose.  The blue thinner hose (included with the S2–the D2 uses white hose), will slide inside the medium black hose and is secured with a clamp.  Once again we use a short section of the medium black hose to connect the thin fuel line to the inlet of the fuel pump.  

Be sure to follow the manual on correct flow direction of the pump.  Some models have an arrow indicating the flow direction.

Recap

Did you get that?  Connected to the Mercedes fuel tap are:  Dorman quick connect –> 6″ section of thicker fuel hose –> white adapter –> short section of medium black fuel hose –> enough blue fuel line to reach fuel pump –> short section of medium black fuel line connected to fuel pump.  There are other ways to achieve this depending on how your kit was equipped.

Routing the Fuel Line – Pump Outlet to Heater

On the outlet side of the fuel pump you will once again use a short medium-sized rubber fuel hose followed by the blue fuel line the rest of the way to the fuel inlet on the heater.  It will take another section of medium black hose to make the attachment at the heater unit.  We placed the small plastic fuel line inside wire loom to help protect it.  Keep the line as tight against the underbody as possible as it will be passing over the driveshaft as well as the very hot exhaust system.  We used a couple of M10-1.5 bolts inserted into factory nuts in the chassis to lightly pinch the fuel line against the body.   See our YouTube video for more detail on how we routed our fuel line.

Espar Electrical Hookup

Next up is the electrical.  This was the toughest part on our older D2 install, but it has gotten much easier with the newer S2 model.  The D2 will likely be discontinued, so if you’re here to install an older D2, please refer to the wiring we discussed in our YouTube video below.  Except for the electrical, the installation of the D2 and S2 are otherwise identical.  The D2 was a bear to figure out–different controller options, and optional temperature sensors and high altitude sensors made the wiring quite complicated.  Thank goodness the newer S2 is all incorporated in one harness. 

There are four components to the wiring harness.  The first component is the fat plug that simply plugs into the heater unit itself.  Second, a 2-wire harness gets routed to the fuel pump.  Third, a four-wire harness plugs directly into the thermostat (Easy Start Pro).  Finally, a three-wire harness with two sizes of red wire and one brown wire are the power and ground.  (The plug with resistor loop is apparently for diagnostic and is not used.)

Making the Espar Wire Connections

The first step is to plug the large flat plug in the harness into the heater unit.  Done!

The two wire harness (usually with gray and brown leads) goes to the fuel pump.  We found it best to remove the section of floor between the driver and passenger seat pedestals.  Thankfully, there is a plastic wiring raceway perfect for routing the wire.  With the wire in this track, look for the big rubber boot inside the driver’s seat pedestal.  Next, go under the van, locate the rubber boot and cut the zip tie.  You can now feed the 2-wire harness under the van.  Route the harness to the fuel pump.  Now click the two ends of this 2-wire loom into the included plastic harness-end.  Orientation of the pins within the plug/harness does not matter.  Once clicked in your harness is complete and can be plugged into the fuel pump.  Pull up the slack back into the cabin and resecure the zip tie on the factory rubber boot.

Connecting the Thermostat (Easy Start Pro)

The thermostat will be used to turn the heater on and off, and it measures the temperature of the air to perform the thermostatic function.  Find a convenient location to mount the thermostat.  Ideally it would be exposed to free-air so the thermostat can correctly measure the air temperature.  Connecting the thermostat to the harness is as simple as plugging it straight into the corresponding plug in the harness.  Done!

Providing Power to the Espar Harness

Next, we need to provide 12-volt power to the Espar harness.  The supply wire will carry a max load of 25 amps, so 10-12 gauge wire should work for most applications.  We used duplex wire, which means a positive and negative wire in the same sheath.  Connect the red positive wire to a 12V power supply and connect the black ground wire to your system ground.  We routed this wire into the passenger seat pedestal where the Espar unit resides.  

Locate the two single red wires included in your kit–the ones with metal terminal-ends.  Cut this harness to size.  (We only kept 8″ or so of this harness.)  Remove the insulation from both wires using a wire stripper.  Now crimp or solder BOTH of these to the red power wire you just brought from your power source. Now grab the fuse holder included in the kit.  Insert the 20 amp and 5 amp fuse into the fuse holder.   Finally, connect the larger sized wire to one side of the 20 amp fuse and connect the thinner red wire to the same side of the 5 amp fuse.

Connecting the Heater Unit to the Power Source

Find the three wire harness coming from the heater unit that includes two sizes of red wire and a brown wire.  There are two steel wire connectors included in the kit.  Crimp these onto the large red and smaller red wires that are part of the heater harness.  Similar to what we did before, attach the larger red wire to the other side of the 20 amp fuse.  Connect the smaller red wire to the other side of the 5 amp fuse.  

Now we need to provide system ground.  In the duplex wire you brought over from your power source, simply connect the negative (black) wire to the brown wire in the Espar harness.  You have now provided both fused power and ground to the heater.  Mount the fuse block where it is will be accessible in the event of a blown fuse.  Our fuse block is mounted on the inside of the seat pedestal and is accessible through the small removable door in the side of the seat pedestal.

Final Touches

You may want to consider replacing the solid seat pedestal door with this vented one (eBay link).  It will allow free air flow to the heater unit for more efficeint operation.  

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