DIY: Replacing factory Espar heater with new off-the-shelf

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Have you found that the Sprinter harness energizes two DIFFERENT wires - one for the Heater Booster operation, and one for the 7-day timer?
I’ve installed the 7 day timer on heater booster (compared to your aux heater config) configurations a couple times. I had to send 12v to the d+ dynamo and the terminal 15 pins when the 7 day timer bacon button was pushed. I don’t think you have a terminal 15 pin since you’re is designed to work with the engine off.

Will the heater fire with the engine running still?

What’s odd is it worked and now it’s not working. Perhaps probe the vehicle side harness both with the engine running and the bacon button on the atc console is pushed and then with the engine off and the 7 day timer button is pushed. Are there any differences?

There is always a chance the heater itself is defective.

Is your auxiliary coolant Pump working? The one one the firewall with a coolant hose coming from the egr? Even if not it should at least try to fire up..

And it could be that load required to drive the atc wire by numbering from the yellow wire doesn’t allow enoug power to that pin.

You were right in the last half mile!!
 
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kentonius

enough to be dangerous...
I’ve installed the 7 day timer on heater booster (compared to your aux heater config) configurations a couple times. I had to send 12v to the d+ dynamo and the terminal 15 pins when the 7 day timer bacon button was pushed. I don’t think you have a terminal 15 pin since you’re is designed to work with the engine off.
Just for giggles, where is the terminal 15 pin for me to verify?


Will the heater fire with the engine running still?
Yes, verified this morning that it will still run with the engine running. What I'm getting used to is the time delay for full heater start - it's not exactly immediate, but takes a total of about 30-45 seconds-ish to get a full start and response (i.e., hand under heater exhaust pipe).


What’s odd is it worked and now it’s not working. Perhaps probe the vehicle side harness both with the engine running and the bacon button on the atc console is pushed and then with the engine off and the 7 day timer button is pushed. Are there any differences?
Will check and report back hopefully today.

There is always a chance the heater itself is defective.
Understandable, but doubtful.

Is your auxiliary coolant Pump working? The one one the firewall with a coolant hose coming from the egr? Even if not it should at least try to fire up..
Yes, aux coolant pump is working. Verified with each start. Works with REST, etc.

And it could be that load required to drive the atc wire by numbering from the yellow wire doesn’t allow enoug power to that pin.
Certainly possible... unless it gets the same 12V signal on the yellow wire from the Booster function?


You were right in the last half mile!!
Sigh... Thanks for being there with me!
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
On the heater booster models, it's pin six (espar harness). It's blue. Not sure if that correlates to your new yeater. You could also jumper off the yellow (D+ Dynamo) wire to get 12v to that pin.

I'd start by probing the vehicle side of the harness to see what the difference is across the harness between the ATC 'on' and 7 day timer 'on'. That should tell you what you need to know. Perhaps there's something wrong with the 7 dt signal???
 

kentonius

enough to be dangerous...
On the heater booster models, it's pin six (espar harness). It's blue. Not sure if that correlates to your new yeater. You could also jumper off the yellow (D+ Dynamo) wire to get 12v to that pin.

I'd start by probing the vehicle side of the harness to see what the difference is across the harness between the ATC 'on' and 7 day timer 'on'. That should tell you what you need to know. Perhaps there's something wrong with the 7 dt signal???
Interesting... so a few things learned today:

1. I might have a unit with an internal temperature sensor as my 56 degrees did not get the heater to start in ANY mode (booster, aux).

2. When turning on the Aux heater (7-day timer bacon button) I get 12V on the yellow wire on the Sprinter harness. Of course, there is always 12V on the red wire.

3. When turning on the booster heater (regular bacon button) I get 12V on the BLUE wire on the Sprinter harness.

Any idea what any of this means? Does it mean that all sprinters with heater boosters had terminal 15, and if you had the 7-day timer (aux heater option), you still have the terminal 15?

I'll try it in the morning - back down below 30 degrees is expected.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Interesting... so a few things learned today:

1. I might have a unit with an internal temperature sensor as my 56 degrees did not get the heater to start in ANY mode (booster, aux).

2. When turning on the Aux heater (7-day timer bacon button) I get 12V on the yellow wire on the Sprinter harness. Of course, there is always 12V on the red wire.

3. When turning on the booster heater (regular bacon button) I get 12V on the BLUE wire on the Sprinter harness.

Any idea what any of this means? Does it mean that all sprinters with heater boosters had terminal 15, and if you had the 7-day timer (aux heater option), you still have the terminal 15?

I'll try it in the morning - back down below 30 degrees is expected.
Okay. So that heater does have a t15 circuit requirement. The blue wire needs 12v when you hit the 7dt bacon button. You could jumper off the d+ dynamo (yellow wire) to the blue wire... but the right way would be to install some relays seeing as we're piggy backing off the d+ With two circuits now.. At the same time they are all just signal wires and don’t require much of a load thus you could get away with it most likely. ��

If it has an internal temp sensor that’s the way it goes short of fooling it or doing some board-level trickery.
 

Midwestdrifter

Engineer In Residence
The D5 has no means to measure ambient temperature. It can only measure the combustion chamber temp via coolant (does it even have a flame sensor?). So I highly doubt its limited by ambient temp. More than likely you need to find a way to link the timers switch on signal to the heaters switch on signal.


Now it is possible that the new D5 is getting some ambient temp data over canbus, but that is not likely either.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
I want to say you’re correct, and yes I was also referring to coolant temp and not amb temp. but my understanding with the newer mbz factory installed d5’s is that they go off the ambient temp sensor. This understanding is not based off of actually working with one.

Yes it has a flame sensor.

the t15 (blue) wire needs 12v. You can link by means the yellow (d+, ‘switch’) wire. There r a few ways to do this.
 

Midwestdrifter

Engineer In Residence
Logically, if the engine has been run at all, the coolant is going to be warm, so the heater can't look at the coolant temp to determine if the air is cold.

Before using one of these 12V supply wires, you might use your meter to ensure the load you are adding isn't a large amount of current. Knowing mercedes, its probably just a relay trigger, so 200mA or so, not a big deal.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Good point on the coolant temp.. so that leaves canbus comm to get ambient temp :idunno:. Perhaps the blue/white diagnostic wire provides that info :idunno: it’s never looked like twisted pair to me but perhaps it is??

K: You could quickly test via waiting for it to warm up, testing it to make sure it won’t start when it’s warm, then dunking the ambient temp sensor (sensor behind front license plate) in a glass of ice and seeing if it will then start. Perhaps if the temps don’t get warm enough take a hair dryer on low (of course you don’t want to melt the thing) to it on the first test. Quick and dirty
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
We may be getting ahead of ourselves as we don’t know for sure if the thing is ambient temp sensitive, but here’s how the ncv3 folks have been tricking the computer to get their Espar to fire any time they want - https://sprinter-source.com/forum/showthread.php?t=35196

Personally, I’d put the resistor through a spdt relay on a switch since there are many other reasons the Sprinter ecm is looking for a correct ambient temp to keep systems happy. Relay could also be activated by the same d+ yellow wire from the 7 day timer...
 
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kentonius

enough to be dangerous...
Hey Team-Espar,

Another update from the start of the morning... While verifying that the heater does in fact work at all, at least when colder out, I tested it this morning. And here are the observations:

1. As in the process of all science and experimentation, I forgot something I did yesterday that I can confirm today. Remember when I mentioned the history of the original unit? I thought I remembered that the PO of the van had pushed BOTH bacon buttons in order for the booster heater (with engine running) to work. Well, when I tested my old unit, I tried all methods and thus we determined that 99% ECU failure. With the new heater, I thought it was inconsequential at first, but then this morning I tried just the booster bacon button.... silence. Turn off booster, try Aux bacon (with engine running).... silence. Push both booster and aux bacon buttons... whoosh! This was also how I enabled the heater upon first install and test - with both buttons on. Why? oh, I just thought it would encourage things... didn't realize they were actually connected. in my van.

I know that this throws some of us for a loop, but it looks like either my van (as example with the PO) and not the heater somehow requires +12V on both the blue and yellow wires to start the heater.

2. Ambient temp sensor as displayed on dash read 40 degrees.

3. Pushing either bacon button causes the heater to go through shut down procedure.

I'm curious as to anyone else using a resistor to trick their van heater into starting above 40 degrees. It's worth a shot, at least to maintain good heater health by running it once a month.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
K: if you want the engine off capability you will need to jumper from yellow wire to blue/pin 6 and then of course keep the jumper from the yellow wire to the purple wire from the old heater to the atc..

Re the resistor, you’ll probably have to go to that thread I referenced to ask folks more about their experiences. I don’t think many, if any, t1n folks here have completed that modification. Once again, and perhaps I’ll be more firm here, you’ll need wire the resistor such that the only time it tricks the ambient temp sensor is when the engine is not running otherwise you run the risk of engine running problems/malfunction and limp mode..
 

Midwestdrifter

Engineer In Residence
If you can figure out how to trigger the fan and coolant pump with a 12V supply, you could easily rig up any external timer or control scheme you wanted. You would hopefully not be limited by any other factory. This assumes you can trigger the D5 using a simple 12V supply to the correct wire.

I am considering doing something similar with my non-D5 van (I added one later). That way I could use switch to trigger the blower/pump (bypass rest limitation) and my D5. Thus serving as a heating backup if my D2 fails.
 
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vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
If you can figure out how to trigger the fan and coolant pump with a 12V supply, you could easily rig up any external timer or control scheme you wanted. You would hopefully not be limited by any other factory. This assumes you can trigger the D5 using a simple 12V supply to the correct wire.

I am considering doing something similar with my non-D5 van (I added one later). That way I could use switch to trigger the blower/pump (bypass rest limitation) and my D5. Thus serving as a heating backup if my D2 fails.
. I’ve done this on a few rigs With 7day timers and 12v thermostats... and by bypassing the rest circuit and going directly to the primary blower circuit you have 0-4 on the blower settings instead of 1-3 with rest. Note for folks without it wired to a house batt bank.... it’s an energy hog and will deplete your starter battery fairly quickly if using the full throttle #4 setting.
 

Nautamaran

2004 140” HRC 2500 (Crewed)
Re: ambient temp sensing, the D5’s harness diagnostics pin is a KWP-2000 line, not canbus. The ATC has a canbus pair, so can know the air temp, but as the ambient air temp sensor is wired to the ECM, not the ATC, the ECM would need to be powered for air temp to be available on the T1N.

-dave
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
thx dave.. i guess it wouldn't be difficult to also send power to the ecm, but it's another piece of work. fun times.
 

Nautamaran

2004 140” HRC 2500 (Crewed)
I was more thinking it unlikely that the espar was expecting to be told the ambient temp via the K-line, and that the ATC was responsible for enforcing the maximum ambient air temperature rule. I’ve never seen an intake air temp sensor listed on an espar parts list, and I’ve never seen any of the espar furnaces in the boats I’ve sailed balk at running in a warm cabin.

-dave
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
so you're telling me the espar is connected directly to the ecm via the k-line blue/white wire but not to the atc via canbus twisted pairs but the atc is sending the temps to the furnace via twisted pair canbus comm? :wtf:
 

Aqua Puttana

Poly - Thread Finder
I haven't read every post in this thread.

I agree with Nautamaran that the Espar is stand alone and the ambient temperature operation suppression comes from somewhere other than the heater.

Is the T1N Espar heater control module sophisticated enough to use CAN bus? I'm thinking that K-line communication is as good as it gets.

I haven't researched it so I have no data.

:cheers: vic
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Perhaps the ncv3 folks will have some input over in their resistor mod thread

Hey there ncv3 folk... Pretty nifty and straight forward mod you guys came up with here. Some of the t1n folks have a thread going to replace the existing factory d5 heater with a new one but the new one has an ambient >39f ambient temp lockout like your factory d5 furnaces do. This resistor should work just as well for us as it has for you, but some of us want to use the furnace with engine off and there’s speculation as to whether it will work without the ecm being on to interpret the sensor information and then broadcasting it over the k line to the heater. It appears some of you are running the furnace with engine off. Does this mean the ecm doesn’t need to be powered on to interpret the ambient temp information and then broadcast? Doesn’t appear anyone is powering on the ecm with the engine off to get this mod to work with the engine off. Perhaps ncv3 and t1n Sprinters are different in that the ecm is always interpreting sensor information (we haven’t tried this so I’m not suggesting this is the case)? Perhaps ours will work just as yours and we don’t need to power on the ecm??
 
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