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Old 10-22-2017, 06:28 AM   #1
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Default Need suggestions for the Factory Aux Hydronic Heater

2005 Sprinter 60,000 mi

I need some advice-

I only used my installed Espar hydronic heater maybe 5 times since I purchased my van brand new almost 13 years ago.

Last winter I used it once, and it worked perfectly, but the next time I tried it, nothing (not even a sound).

I probably have tried 5-7 re-tries over the past year since then, and it's dead.

I understand you only get a number of cumulative re-start tries over the heater's lifetime and you need special equipment to re-set it, but given that mine wouldn't work with zero previous no-starts, I suspect my heater needs repair for something beyond re-start lock-out reset.

So, should I just remove it, or are their in-vehicle checks one can do to troubleshoot it first?

If removal is in order, is there a sticky somewhere outlining the procedure. I looked/searched but found nothing.

It looks like removing it would be a challenge given how deep the thing is buried and the relatively small hole it would need to come up and out of. I imagine at minimum, removing the battery and it's tray would be the first order of business.

Looking down at the heater, there is a clear vinyl tube tucked behind a wire harness against the wheel house that is chewed on one end, with the other end terminating through a grommet next to the Espar exhaust. Not sure if this is a heater drain or what it was for at one time, but it appears chewed by a mouse (they cause grief around here with wiring and tubing). It can be seen in the photo to the right of the 3 red wires where the red arrow is pointing.

Click to enlarge-

I'd imagine to use the vehicle with the heater removed would use of some 5/8" (?) heater hose to connect the two metal coolant lines together that connected to the heater. Does the small nylon (?) fuel line need to be capped, or does the heater suck the fuel to it?

Thanks for any advice or direction. It would be nice to have the heater working since all of my trips in our new location are 5 miles or less, and in the winter I doubt the temp gauge will come off the peg for weeks, and I know that is really bad for the engine. Preheating and fast warm-up would improve it a lot I suspect.


Last edited by bobinyelm; 10-22-2017 at 06:51 AM.
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Old 10-22-2017, 07:57 AM   #2
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Default Re: Need suggestions for the Factory Aux Hydronic Heater

Hi Bob,

That bit of tubing could be the battery breather...it usually pushes into the battery and goes out under the van near the heater exhaust.

If the heater isn't leaking I wouldn't bother removing it; however, with the headlight out it's a lot easier to get at.

You could check the relevant fuse, or check for power at the switch or heater with a multimeter.

I think they also need the diesel tank to be at least 1/4 full to work.

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Old 10-22-2017, 10:07 AM   #3
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Default Re: Need suggestions for the Factory Aux Hydronic Heater

A sprinter compatible scanner can supposedly read codes from the heater booster unit.

A fairly common cause of nothing happening at startup is a seized or stuck blower motor. Try plugging the exhaust (mostly) and blowing compressed air through it. Do the same for the intake in reverse. The blower should be heard spinning up as the compressed air goes through. This may be enough to free up the motor and clean the commutator.
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Old 10-23-2017, 10:42 PM   #4
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Default Re: Need suggestions for the Factory Aux Hydronic Heater

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.

Added by AP.

Originally Posted by Aqua Puttana View Post
It just occurred to me for the BOOSTER Heater. The engine may need definitely needs to be running with the bowtie (bacon) switch activated before pulling the fuses (25 and 10 amp) under the driver seat for the reset attempt. Until the conditions for enable are in place (engine running, bowtie switch on), pulling and replacing the fuses may will not work for reset.

2005 158 high roof 200k or so

Last edited by Aqua Puttana; 11-10-2018 at 02:10 PM. Reason: Add engine running comment
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Old 10-29-2017, 03:54 PM   #5
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Default Re: Need suggestions for the Factory Aux Hydronic Heater

you do have over a quarter tank left, correct? On mine a 1/4 tank is around the half way mark on the gauge...
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Old 11-03-2017, 02:32 AM   #6
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Default Re: Need suggestions for the Factory Aux Hydronic Heater

Hi Bob, if at a guess from your user name you are in Washington, you might contact these folks in Seattle: AMC Cliffv's Marine.


I found Cliff was pretty knowledgable about these units, has parts and he has the code reader which determined mine had a bad control unit (which I haven't been able to find a replacement for).

One thing he mentioned to me is that biodiesel will kill these units dead.


Last edited by EEJ; 11-03-2017 at 02:34 AM.
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