Some Condensed Espar Notes

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Aqua Puttana

Poly - Thread Finder
Some Condensed Information from this (same) thread that may help with troubleshooting.
All of the information is from my Some 2004 Espar Heater Notes thread so take the time and go back for pictures and schematic references. This is not a "How to". Some basic multi-meter and other troubleshooting techniques will be needed.

At some point you may just need to bite the bullet and remove the Espar for testing and cleaning. It isn't that difficult.

Some other 2004 Espar Booster Heater threads which I've posted are here:

Remove Espar Heater from T1N

General Espar Heater Wiring Information

Cabin Fan Resistor Circuits

T1N Booster Heater Wireless Control


First: The Varnish Sniffers across the pond have been busy revealing interesting information about the Espar heaters since I last visited their site. Visit the site.

Some general information for the Espar heaters.

All this information is out in other threads. I am repeating. A search can be your friend.

The basic Espar heaters are a small self contained oil burner furnace as to firing. The heaters can be installed stand alone in boats and vehicles. The little furnace has a built in combustion control module for the ignition, blower speed, flame monitoring, operating temperature control, and overtemp safety monitor.

To just fire up, the Espar furnace needs a fuel supply (pulse pump), combustion air (internal fan), and an ignition source (glow pin). The native combustion controls are just sitting there waiting for your Sprinter to wake it up properly.

The basic external requirements to fire up are:

Constant 12 volts to pin #1.
A proper negative ground connection pin #2.
A connection (wire) out to the dosing pump pin #4 (It is a conditioned signal. Not just 12 VDC.).
A 12 volt enable signal to pin #6.
A 12 volt enable signal to pin #7.

Pin #5 is for communication. It is not required.

The circulation pump is not required for the heater to fire up. The Espar control has no idea what the MB aux electric coolant pump is doing, or not doing until the heater goes to over-temperature. Without proper coolant circulation the Espar heater will shut down on overtemp safety in a short time.

The Espar heater does run through an internal system check before firing. If there is a problem with the glow pin, flame sensor, blower, etc, then that will prevent the Espar heater from getting to startup. (There may also be some sort of verification for an external relay component. I say that because there have been reports of the Sprinter Espar throwing a coolant pump code failure. That is even though the MB Aux Electric Coolant Pump has no connection to the native Espar controls. The Aux Espar with two electrical connectors may have a direct connection.)

Here is a basic diagram.

View attachment 81050

Added: As Vanski pointed out, the Espar coolant type heaters can even be test fired with no coolant. I wouldn't allow it to run for more than a very short time without coolant though. It will very quickly over heat and stress components.

My Espar start overview.

What I learned after it fired.
The earlier times that I thought it was firing it was just burning fuel in the glow plug chamber which produced white smoke and did not ignite the main chamber. Actually evaporating might be a better term than "burning".

The faulty operation sequence as I recall it.
The engine noise at idle makes it hard to be certain of some noises. After starting the engine the Espar combustion fan would cycle for a quick ramp up. After a short fan run cycle to purge the combustion chamber the fuel would pulse in. The heater would begin pouring out white smoke. I thought that meant it was firing because the combustion fan would ramp up. After ramp up I'd see even more white smoke. Then the fuel pump would stop, the fan would ramp down, raw diesel fuel would drip out the exhaust (I later learned that my muffler packing was soaked with fuel.), the fan would run a while (combustion chamber purge) and then slow down. After (if?) the first start fails, the blower runs on a low speed into a 2nd start attempt. If the 2nd start fails, the blower continues to run through a standard cooldown cycle and then locks out for no more attempts until a power down reset.

Each failed ignition attempt dumps about 1 1/2 teaspoons of unburned (raw) diesel into the combustion chamber. No ignition at all = x2 start attempts = approx. 3 teaspoons of fuel. The combustion fan carries that fuel to the exhaust system. Once the muffler stuffing is saturated the fuel will spill out from the exhaust system.

I learned that when the heater actually fires off there was just a little white smoke and then the Espar would begin to roar. You will recognize the roar as opposed to just the fan ramping up. It sounds like a low rubble not just a whine. The whine is just the fan turning up to very high speed. For each start attempt the fan will run and the fuel pumps until the flame sensor kicks into the circuit and realizes that there is no main flame. It then stops the fuel and the fan ramps back down, but not shut the fan down right away. As I said, the white smoke I saw is just the glow plug chamber fuel burning (evaporating?) and not actually igniting the main burner.

Firing correctly = A little white smoke then No Smoke. Not enough air = Black smoke. Unburned fuel = White smoke.

I've noticed some comments about the dash temperature settings being related to the Booster Heater and Aux Heater operating. To my knowledge the Espar doesn't care what positions that the OEM Cabin fan/heater controls are in.

Once the Espar heaters are enabled and fired up the temperature control is maintained by a coolant temperature sensor contained within the Espar heater module. Given proper coolant circulation the heater will run until the coolant temperature reaches setpoint.

There are 2 ea. control setpoints. The first lower temperature will trigger the Espar to go to low power output. The higher (167F if memory serves) will trigger a shutdown of all firing. There is an even higher over-temperature limit, but that shouldn't come into play when proper coolant circulation is maintained.

Except for the Espar dedicated dash controls, the OEM cabin temperature controls do not affect the Espar operation once it is enabled.

:2cents: vic

I've read that Espar heaters "Lock out" after some failed start/ignition attempts. I don't find that true with my 2004.

Isn't it true that after a number of failures to fire, the Espar locks itself out and needs to be reset with an MB star tool?
I've read that. From my research that may be the mode of a native Espar diesel fired heater. I've read that after so many start attempts the native Espar heater locks out and needs to be reset using the proprietary Espar access scan tool. OR maybe the permanent lockouts are related to specific component failures which are monitored by the Espar computer and people assume it has locked out related to a couple start attempts. :idunno:

My experience:
My 2004 heater main burner never fired for the first 6+ years that I owned my van. I tried it more than a few times over the years. Each time the most I would get was white smoke = unburned fuel. The Ignition Air Duct was plugged solid so the main burner never fired. When the button was pushed the red dash LED would light, the heater would try to start two times in succession and then would lock out, but not permanently. After an engine shutdown and restart it would again give two white smoke cycles.

After I cleaned the burner and screwed up the screen "wick" metering into the glow plug chamber I tried many more x2 white smoke cycles. There was never a permanent lockout. The heater runs fine now.

So, my experience shows that the Sprinterized Espar control module doesn't lock out after a failed ignition sequence. The 2 x start tries are allowed and then it prevents any further starts until power off/on. That is not as described for the native Espar control.
This thread has some good info.

Espar Booster Heater Not Starting - Info near Write-up Status


Espar D5 Fuel Quantity Test

Fuel Quantity Test
The fuel Quantity should be tested if the heater has difficulty
starting or maintaining a flame.

Note: Measure the fuel quantity when the battery is
sufficiently charged. At least 11V and at
most 13V should be applied at the control
unit during measurement.

• Remove metering pump cover in the cases of SC versions.
• Pull the fuel line off the combustion chamber and insert
into a graduated measuring glass
• Switch the heater on, when fuel delivery is uniform
(approximately 40 seconds after switching on), the fuel
line is full and bled.
• Switch heater off
• Empty measuring glass and replace

• Switch heater on
• Fuel delivery stars automatically approximately 40
seconds after switching on
• Hold the graduated measuring glass at the glow pin
height during measurement
• After 90 seconds of fuel delivery, it will shut off
• Switch heater off.
• Read off quantity of fuel delivery in the graduated
measuring glass


Nominal value


Hydronic D5W SC

8.6 cm3 / 90 seconds - Maximum Qty
7.5 cm3 / 90 seconds - Minimum Qty

7.5 ML = approx. 1 1/2 teaspoons

I found that an old Baby Medicine Dosing Spoon worked perfectly to measure the fuel output. The output from my pump was at the 7.5 ML low end of the specification. (Note that the 90 second test includes a combination of low pulse and high pulse pump operation. Low pulse = ignition cycle. High pulse = ramp up until no flame sensor cutoff.)

View attachment 56483

The fuel doesn't "pump" out it more trickles out. You can feel the fuel line pulse as the fuel is "pumped".

These Sprinter wire colors and function are deciphered from a few different technical sources and schematics. You will not likely find this info in many places. MB doesn't make it easy to track down using just their Service Manual schematics. The MB OEM controls are a step child to Espar that they have no interest in.

Sprinter OEM Espar Plug Info

Chamber (Pin) - Cross section/Colour - Function

Pin #1 - 1,5 red - plus supply, terminal +30 Sprinter = Orange? (Red/? - Heavy Wire) - All (8W-42-11)
Pin #2 - 1,5 brown - minus supply, terminal –31 Sprinter = Brown (Heavy Wire) - All (8W-42-11)
Pin #3 - 0,5 black/red - not in use? Sprinter = Blue/Yellow - Program Timer Only - Fan Stage 1 Relay = REST Low Spd (8W-42-08)
Pin #4 - 0,5 green - plus signal, dosing pump Sprinter = Dark Green - All (8W-42-11)
Pin #5 - 0,5 blue/white - diagnosis Sprinter = Blue/Red - All (8W-42-10)
Pin #6 - 0,5 blue - terminal 15 Sprinter = Blue - Program Timer, Black/Blue/Orange - Except Program Timer (8W-42-10, 8W-42-11)
Pin #7 - 0,5 yellow - D+ dynamo Sprinter = Yellow - Program Timer. Blue - Except Program Timer (8W-42-10)
Pin #8 - 0,5 black/white - not in use?? Sprinter = Blue/Yellow (8W-42-09)
Pin #8 Clarification Note:
Cabin Heater Module aka Program Timer = Circulation Pump Relay - Cabin Heater Module (Relay Block)
REST System aka Except Program Timer = ATC Module - No Relay, Direct (Heater Booster Mode) (8W-42-09)

*The Dash Inset Control aka Program Timer will have a Circulation Pump Relay and a Stage 1 (Low Spd) Fan Relay under the driver seat.
* The Booster Heater aka Except Program Timer doesn't have any related relays under the seat.The ATC module does the logic/control for the Booster Heater/REST pump and fan.


Have fun.

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Aqua Puttana

Poly - Thread Finder
Apparently a reset can be accomplished without a scan tool or control head communication. Thanks goes to SkyGypsy. :thumbup:

If the unit doesn't start, then you can clear and reset the unit by powering it up, then pulling the fuses underneath the driver seat. I have done this several times and gone from no response to startup in moments.

I have done a full overhaul on my unit. I should post a write up on it. I have the factory manual, maybe I will post it on my website for others to download.
I have not tried the above. It did work. I pulled the 25 amp fuse under the seat.

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Aqua Puttana

Poly - Thread Finder
An Espar Aux Timer Control possible hack.

If the console dash timer/controller fails there is a temporary, maybe permanent hack.

A mechanical thermostat or twist timer can be wired from 12v+ to the yellow enable wire. A simple switch would also work, but perhaps a temperature/time control of some sort is wanted.

An example of a mechanical stat.
An RV style mechanical stat will also work. More $$$.

As an aside for northern home owners who travel:
I used this stat as a backup freeze protection addition to my home programmable thermostat.

Most programmable stats are NOT fail safe = no freeze protection. A cheap thermostat will provide that protection. The lowest temperature on the above stat is 50F. That was great for my freeze protection (No off switch. I set 55F.), but will need an off/on switch for the Espar hack use.

A twist timer example.

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