espar auxiliary heater with DRB III

I would like to bring my van to the local Dodge dealer to see if they can "reset" a possibly locked out Espar ECU. Several threads here indicate that the DRB III may be capable of such a reset, but I did not find any definite evidence that this has been done. Can anyone confirm if they've had any success "resetting", or provide any helpful details about how it is done? I have a feeling this is going to be an unusual request to the dealer, and any advice I can provide them will likely save a lot of $$.

Background info: I have recently rebuilt (cleaned, replaced gaskets) in my auxiliary heater. It has the simple controls, not the 7 day timer, and I'm planning to bypass the anyway and run manually, once I get it working. The unit is getting 12V between pin 1 and 2. Jumping +12V to pin 6 is supposed to start the heater, but it does nothing- no noises, no fuel pump pulses coming out. The fuel pump works fine by itself when I tap 12V across it. I believe the ECU is either dead or locked.


Patrick of M

2005 T1N 2500 (NA spec)
When you replaced the gaskets did you check that the fan moved freely? In the start up protocol the fan is the first thing that moves, if it doesn't start nothing else starts. seems like nothing is happening because the fan is jammed.. I unjammed one by spraying silicone aerosol lube under the edge of the fan turbine while manually turning it. This is possible with the Espar in situ if you take the fan cover off(4 top screws, 2 side screws). The only problem is the aerosol is flammable and you might ignite it in the boiler which could be explosive, so proceed with caution.
Hi Patrick, the fan did spin freely by hand, but I did not test it with a 9V battery as some have suggested. I will do that next, along with seeing if I can get the glow pin to heat up.

Another piece of evidence I did not mention- the plastic covers on my heater were warped, which makes me think it overheated.. The auxiliary coolant pump had failed and I have since fixed it.

I also did not find any info about how to test the flame and temp sensors, it would be great to do this while it's out


I found a D5 maintenance manual somewhere on line a few years ago that gave resistance values for the sensors at a range of temperatures. Sorry I don't recall where. Keep us posted. I got to about the same stage you're at with a heater that had zero response, but all the components that I could check appeared OK, including the fan motor. My heater is so clean I wonder if it has ever been operated. I suspect the ECU is shot, but I don't think I've ever had a clear answer on the lockout issue.


2004 140” SHC U.S. T1N
From reading Vic/AP’s experiments I *thought* there was a second lockout signal coming from the aux coolant pump, not just the pin 6 enable. Something MB had Espar put in the Sprinter heater’s controller.

Or not? I’ve never worked on one... just rings a bell.


To reset a locked out heater, you simply turn it on and pull the fuses then reinsert them. Your overheat sensors are probably at fault. The insulation on the wires crumbles and they short. You must remove the top warped plastic to cHeck that.

Goofy foot

sliding left...
If your covers warped, then your Espar overheated, most likely because your recirculation pump died. Start there. I had the exact same problem you have. Pay particular attention to not damaging the "wick" inside the "D shaped port" as it's easy to do. Some useful photos and why the recirc pumps fail so commonly.


Aqua Puttana

Poly - Thread Finder
... Some useful photos and why the recirc pumps fail so commonly.
The good news is that your first picture shows you can buy parts as needed. Back in the 60's it was good to have the bread on hand to buy things.

:cheers: vic

P.S. - Younger owners are scratching their heads. :hmmm:
Younger owners are scratching their heads
Haha, yes. Thanks for the pictures.

I tested the coolant sensors- both show about 24K ohms at 40ish F ambient temp, falling to 4-5K ohms when heated with a hair dryer. Sounds normal.

My 9V battery only has 7volts, and fan does not spin with that connected. Next step, measuring voltage to fan with unit installed and wired in Sprinter.

Pay particular attention to not damaging the "wick" inside the "D shaped port"
Mine did not have a wick (EDIT: NEVERMIND, IT WAS THERE), it was totally missing. Has anyone made a suitable replacement or run without? I will come to that problem eventually, but first need to to get electrical working.
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Goofy foot

sliding left...
Look carefully for the wick. As I remember it is around the perimeter of where the D-port angles to the intake, an inch or so in from the D-port opening. It doesnt cover the whole opening. Vic would know better than I. Don't blow high pressure compressed air, or a stiff brush up inside that port. Tender, like penis surgery! :smirk:

That fan should spin with as little as 7 volts I believe. Start there. As I remember I did blow about 60 psi compressed air up under the fan housing. Mine spun like Democrat's on CNN !
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Aqua Puttana

Poly - Thread Finder
Look carefully for the wick. As I remember it is around the perimeter of where the D-port angles to the intake, an inch or so in from the D-port opening. It doesn't cover the whole opening.
If your 2006 burner has the older style D shaped glow pin hole like Goofy Foot

then the flat mesh is on the flat wall of the D.

If you have the newer style burner with fuel strainer (fuel pipe detaches) you have a different D shaped design.

On some D opening heaters the mesh covers the little side hole. On others it just surrounds it. One tech mentioned that he sometimes pokes a hole in the ones which come completely covered to help prevent soot from blocking the small hole.

The mesh starts at the top and as the fuel trickles down the mesh creates a thinner film of fuel to be ignited by the glow pin. As Goofyfoot mentioned, be very careful when cleaning the D opening. You don't want to damage the mesh or disturb the fuel metering structure it is connected with. I used a 22 caliber barrel bore brush with solvent.


Note the Ignition Air Duct or Channel. On my heater that was completely blocked. It almost seemed like a compound rather than just dirt. That might explain that my heater is in such good condition by having not operated since new. That air duct is critical to igniting the heater. In hindsight, I should have just cleared that duct, cleaned the burner "D" glow chamber with carburetor cleaner (as opposed to digging at the soot/carbon build-up with picking tools - screwing up the screen), and lastly run a fine wire into the fuel pipe with a carb cleaner flush. I'm convinced that would have restored my heater to operation. I base that on the fact that, except repairing the self-inflicted damage to my burner screen "wick", all that I did was to clean my heater fuel and air passages for the heater to work properly.


A note for cleaning the Fuel Strainer type burner.

The back curved walls area of my integral fuel pipe Burner Burner 25 1922 10 00 00 "D" shaped glow pin chamber is a solid piece. Based upon visual inspection the brand new Fuel Strainer type Burner 25.2216.10.0000 aka stamped 25 2149 10 00 02 also has a solid back curved wall. I inspected the brand new Fuel Strainer glow plug chamber. Unfortunately I can't get a good picture inside so I'll describe it as best I can.

Refer to the 2nd burner picture in post #2 above for an idea of the screen and 3/16" hole position.

The Fuel Strainer burner is non-magnetic and appears to be stainless steel. The back curved walls area of the "D" glow pin chamber is solid. The flat wall has a screen embedded to it on the inside (in the glow pin chamber). An approximately 3/16" hole is in the flat wall out into an intermediate chamber. The screen surrounds that hole, but doesn't cover it. The screen disappears into a slot at the top of the "D" chamber flat wall. There are no other holes which I can see other than the tightly filled screen slot and 3/16" hole out to the intermediate chamber.

My cleaning suggestion applies to the Fuel Strainer burner the same as the integral fuel pipe style. It is best to rely on solvents like carburetor cleaner and avoid poking around too much. The screen attached to the wall may need cleaning, but you don't want to disturb it too much.

The two different fuel pipe entries leaves me a bit unsure as to actual primary ignition. I know that the screen/slot "wick" design is critical for both burner styles. It is interesting that the integral fuel pipe disappears behind the "D" chamber at the rear in contrast to the Fuel Strainer fuel pipe metering fuel into the "D" chamber from the front or glow plug end. I'm convinced that the glow plug produced flame ignites the fuel and exits thru the 3/16" hole into the intermediate chamber. The upstream air pressure via the Ignition Air Duct (Kanal) should overcome the larger downstream air opening (less pressure) so that the glow chamber flame moves out into the intermediate burner chamber. That same Ignition Air Duct air flow must also carry the fuel out to the glow plug chamber in any burner which has the Fuel Strainer. The heaters can be mounted in various orientations so the fuel isn't just gravity fed.

Anyway, things need to be clean and open enough, but not open too much, for flow. I know that the screen and slot, the Ignition Air Duct, fuel pipe, strainer, etc. needs to be clean enough for the heater to work.

The entire convoluted information is here.

Extra comments...
Tender, like penis surgery! :smirk:

That fan should spin with as little as 7 volts I believe. Start there. As I remember I did blow about 60 psi compressed air up under the fan housing. Mine spun like Democrat's on CNN !
Nice. The fan comment should result in a smile regardless of your political persuasions.

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Update: With a new 9V battery the fan spins, and I also used it to heat up the glow pin to the point where I couldn't touch it in <10 seconds.

The only sensor that has not yet been tested is the exhaust gas temp (or flame?) sensor. I will try to search about how to do that next, in the interest of completing the testing info.

I did not get around to testing for power to the fan with the heater wired to the van yet, but I'm 90% sure it's not going to get any. I suspect either a bad ECU or EGT sensor.

I looked closer for the mesh screen, here is what I found.

To reset a locked out heater, you simply turn it on and pull the fuses then reinsert them.
I will give this a try as well, but, how is it any different than unplugging/re-plugging in the heater from the vehicle harness?

Aqua Puttana

Poly - Thread Finder
I've seen "mesh" that looks similar. I would clean/flush it out with some spray carburetor cleaner. Try not to disturb the structure.

Unplugging the entire connector de-powers all at once which may not affect the memory state. Leaving power on part of the Espar circuits (heater powered on) and pulling the 25 amp fuse under the driver seat seems to clear the memory or reset.



I don't know how it's different, but that is the procedure. And it has worked for me on several occasions.

My heater tests returned these results at 92F. I have the workshop manual somewhere but I'm on my phone now. It's easy enough to find.

Test results
Glow pin - 0.6 ohms
Flame sensor - 1132 ohms
OH sensor - 7.25K ohms
Temp Sensor - 7.25K ohms

They were all within spec.

My fix was ultimately changing the burner. I'll keep the old one and soak it in parts cleaner to try to clean the screen if ever needed. So far at 8000ft above sea level with a fuel line pinch and daily use it works perfectly. It looks like it's been through hell and back but it works.
The workshop manual you refer to- is it an Espar manual, or Dodge?

The 2006 dodge manual has this
"Flame Sensor Resistance
The normal range for the Flame Sensor is from 750
ohms to 2270 ohms. The value indicates the momentary
resistance of the Flame Sensor."

But nothing on the other sensors. Is the flame sensor supposed to change resistance with presence of heat/flame, or is it one of the rectifier type?

I would like to get to the bottom of the fuse pull test, because since my (and seemingly many other) heater has a modified wiring scheme to allow unlimited engine-off operation. To turn on I apply battery voltage to pin 6. I assume removing the fuse would remove power from pin 1, and I should still give power to pin 6 to represent "on" and enable the ECU reset?

Pin 7 is called "D+ Dynamo" Anyone know what that means? I am not connecting anything to Pin 7. I'd love to test the unit the normal way, eliminating custom wiring, but the van engine can't run right now for other reasons.
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Goofy foot

sliding left...
Markx, I doubt it's your ECU...blanking on what an EGT sensor is . I haven't read where you mentioned your recirculation pump yet. Or cleaning your grounding point. Your Espar covers warped because your recirculation pump has failed. Have you checked it yet ? Your ATC is also in the loop. I would try to find someone in your area with a DAS scanner (C3,C4) or DRB3 or an Espar scanner(available). Be will solve it ! You also have to have the required amount of fuel in your tank ( over 1/4???) as well as coolant temp under 180F I think.
Exhaust Gas Temp- Espar calls it the flame sensor, and I should too, but it seems too far away for an actual flame to touch. From my memory (it is not in front of me at the moment), the sensor is located in the exhaust stream right before the exit to the muffler pipe. I am still wondering if it is a true flame sensor or a temperature sensor.

As for the recirc pump, I just replaced with brand new. I had rebuilt the old one with new brushes but was not confident enough in the repair to justify saving $70 for a brand new Bosch from FCP Euro.
As for the 1/4 tank and coolant temp, I think I have bypassed all that by putting power right to pin 6. The heater ECU should know nothing except that it is being commanded to run, right? I know there is enough fuel because tapping 12V across the espar fuel pump terminals produces nice little drips of diesel.

Goofy foot

sliding left...
Do you hear/feel your recirc pump operating when you start your engine? (important) (It's why your covers warped) So, if you have, and it's humming along, then use the appropriate scanner to test/clear the ZUH (booster heater).

Goofy foot

sliding left...
It's more about stored memory, than dripping fuel I think, I'm not sure about the interaction between Espar/Sprinter ECU talk.....I think that's also an issue... I'm just saying....Use the appropriate scanner to clear/test.....It's how a rookie like me , got mine going again after recirc pump failure and resultant code lockouts. Good Luck !

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