ESPAR sanity check


New member
Looking for a quick read on if I'm interpreting the troubleshooting instructions correctly. Have read through all the various threads, etc. Here's the specifics:

06 T1N passenger with aux heat, REST & 7 day timer. (Also rear heat)

ESPAR was working fine a year or more ago, but we don't use it much. Tried it recently, and it would not start. Here's the specifics:

- No codes on 7 day (no diag wire, yet)
- Interior fan comes on lowest (1) setting
- I think I hear the espar fan running
- Dosing pump clicks after a bit, 8-10 times. Then stops. Then a minute later does the same.
- No smoke, no roar, no noticeable fuel drips
- What I though was the circ pump was not running. (Up on firewall near blower resistor). Now I'm thinking that was not it, as most pics are different and lower.

Since it attempts to start, based on troubleshooting, it makes it sound like:
- It's not locked (no code on 7 day, and it tries to start)
- Not blower problem, as it tries to start
- Not coolant pump as it tries to start???

Likely suspects:

- No fuel
- Plugged air/exhausts
- Glow pin??? (hard to tell on that one)

I'm going to confirm fuel and no blockages.

But would greatly appreciate if any of you ESPAR savvy types could confirm my interpretation of the troubleshooting docs and results are correct. IE: Not locked up, not likely coolant pump, etc.

I'm going to crank the van and see if it will start then, which I think isolates out the coolant pump.

Any input appreciated!


'05 Snow Camper, '17 170 4x4, Adventure Vissionary
You’re on the right track! Little confusing though as to whether or not your aux coolant pump is pumping...Follow the coolant line from the egr. The next stop is the aux cp. turn on your rest. If it not vibrating that’s most likely your problem. if not vibrating , the heater will shut down due to the temp sensor working properly. If the aux cp is working it may just be ‘clogged’ as you suspect but not necessarily due to air flow. Think glow pin buildup. This happened to me! Remedy - disconnecting the fuel line down stream from fuel pump and running a line into a jug of kerosene instead of diesel. It’ll burn nice and hot and clean out deposits. I do this once a year now as maintenance. Thanks for the reminder....
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UK 2004 T1N 313CDi
I'm going to stick my neck out and say Flame Sensor Failure!

My eSpar would do pretty much the same, run up the fan, start the dosing pump then shut down. The unburnt fuel would eventually drip out of the exhaust. After around eight to ten failed starts the unit then locked out.

A scan with an MB SDS (after resetting the lock out) said the Flame Sensor had failed and then opening it up and performing a resistance test confirmed this.

I installed a new sensor and all is now good.


Edit to add: The Flame Sensor confirms the burner has lit as opposed to the Overheat Sensor which shuts the until down if the coolant is not circulating.


I think Keith is on a good path there.

Let me just put in my 2 cents in case my situatin resonates with yours.

Last year when I got the van, I tried to start the Espar hydronic with the 7 day timmer. It would start, clic the fuel pump, run for a very short time (2 minutes? maybe less) and then shut down.

In my case it was the coolant pump on the firewall that was not running. I ordered and installed a new one, only to realise that the pump was fine, it was the positive wire going into the connector thas was fully corroded, so also look into that.

The reason I was able to confirm that my coolant pump wasn't runing, was that I was touching the coolant out hose on the Espar while it was trying to run. It was quite easy to notice that it was getting hot to the touche with a bare hand. I then deducted that it was shutting down in "over-temp" because ther was no circulation.

Good luck!

Aqua Puttana

Poly - Thread Finder
My :2cents:

The Sprinter Aux Espar heater will fire whether the electric coolant pump is operable or not. There is no pump/flow feedback. There is only the over-temperature safety cutoff.

The glow pin and other components are checked by the combustion module during the pre-start routine. If the glow pin doesn't pass muster I wouldn't expect the combustion sequence to advance to the fuel pump operating. (I guess that Cheyenne Keith's information contradicts that. Perhaps the glow pin can be non-functional and still pass the pre-start testing.)

The Espar combustion fan ramps up momentarily during initial power up. After the fan goes to lower speed it can be difficult to hear.

After a few aborted start attempts which include the fuel pump clicking up to high speed, I would expect to see some unburned fuel dripping. That said, if the exhaust system is tight the muffler media can absorb and hold quite a bit of fuel.

When the fuel pump is pumping fuel properly into the Espar the plastic line can be seen jumping a bit. If the fuel line isn't jumping it is a clue that it may not be pumping. That is not total verification positive or negative.

During the start attempt listen for the fuel pump tapping and then observe the muffler outlet. If you see a puff of white smoke then the glow pin is functional and the heater is getting at least some fuel. No puff could indicate a lack of fuel or ignition.




Edit to add: The Flame Sensor confirms the burner has lit as opposed to the Overheat Sensor which shuts the until down if the coolant is not circulating.
That is true, but I believe that the flame verification is a simple temperature sensor, not a flame sensor proper eg. - Kanthal flame rod type current monitor.
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UK 2004 T1N 313CDi
Cheyenne, thank you, that is the most useful manual I have seen yet, and even though the hardware is slightly different than what I have, the electrical side matches.

Patrick of M

2005 T1N 2500 (NA spec)
Correct Vic, look at page 20 of the attached pdf for a Temperature v Resistance graph.

View attachment 92680
Great D5 link.thank you. I'm in the reassembly stage, (and the freezing my ass off stage). No mention of gasket sealer/cement inthe linked manual.
It seeems the gaskets go in without any extra product, yet during prep it sure seemed something was used as the paper fiber gasket on the fan assembly, as it was very stuck on, and clean up/prep,was lengthy.
So, dry assembly or high temp gasket cement?

Aqua Puttana

Poly - Thread Finder
Assemble dry.

I thought that a bit of Never-Seez would be a good idea for the burner gasket. Wrong. It didn't help and may have softened the gasket a bit.

The gasket appears to have graphite on the face. I wouldn't use anything. If you disturbed the water chamber, maybe a tiny bit of silicone lube on the water chamber O-ring seal.

Depending upon condition, if the graphite gasket comes apart basically intact, it can sometimes be re-used. It is not holding back much pressure.

:2cents: vic


New member
Thanks all, this helps immensely! I'm going to go ahead and order the pins to put in the diagnostic line as well.

I did not see even a puff of smoke, so I'm suspecting glow pin stuff in some form.


'05 Snow Camper, '17 170 4x4, Adventure Vissionary
I’ve had a flame sensor and GP failure as well.... but, you’re signing yourself up for unnecessary work and cost if it is something as simple as the aux cp or it being in need of a good cleaning or better yet a good hot burn with kerosene. Been down all these roads with successful outcomes. No need to make this more complicated than it needs to be.... of course working on these things can be fun and if you’re looking to understand it better in general, get the codes and start throwing parts at it!
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