General Espar Heater Wiring Information

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220629

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After a false start 2014/01/01 Edit: a few false starts, I'm starting this thread in an attempt to condense some of the Sprinter Espar heater wiring information into one place.

There is much more information available in various threads in the Database section.

First let me say that I haven't yet repaired my 2004 Espar Hydronic Booster heater. Because it is not working edit: It works now. (as yet /still), I have not modified it to run as an engine warming unit without the engine operating. I have however learned some things and dug up quite a bit of information related to the Sprinter standard Espar heaters and now Sprinter Espar D5 units with custom controls.

One thing that I have learned is that there is some information floating around which I don't believe is completely accurate as to the actual wiring of the Sprinter heater. Some of that is in the Sprinter Service Manuals.

The standard ESPAR D5 diesel fired heater units are designed to be installed into many different vehicles and even boats. The design requires only proper voltage, proper fuel, and an enable signal for the heater to fire up and run. MB has requested some modifications of the controls, but even the Sprinter heaters are still basically standard. The Espar heaters can be enabled by different control configurations. Those options range from a simple on-off switch, to a basic thermostat, up to more complex programmable controls.

Note: One expert I've communicated with warned that Bio-fuel is a problem with the Espar heaters. He even cautions against 5% and suggests installing a "Day Tank" and running the heaters on Kerosene. I can't disagree, but installing a day tank with easy fill capability is likely easier said than done. He mentioned that a coffee colored residue which is harder to clean than the normal black soot is one evidence of bio-fuel rlated problems.

...

My thought process/approach is more that the standard Hydronic Espar Heater is a stand alone unit. It requires proper voltage (constant Pin #1 and "enable" Pin #7), proper fuel (a metered pulsed supply), combustion air (internal fan), and enough coolant flow to keep the water and combustion chamber shell temperatures within proper range (electric pump or engine pump). What MB does to the unit is Sprinter specific.

If you satisfy the basic conditions above the Espar heater will run using its own internal control module. ...

Here is what the Sprinter manual describes as the Aux Electric Coolant (aka Water) Pump operation.

*************************

Sprinter Electric Coolant Pump Operation

From VA Manual - Plumbing 24 - 75

OPERATION

The electric coolant pump is controlled by the ATC
A/C-heater control and is only operational when the
ignition switch is on under the following conditions:
(1) Vehicle speed below 27 Km/h (17 mph).
(2) Coolant temperature above 65° C (150° F) but
less than 110° C (230 ° F).
(3) Any blower motor speed setting.
(4) Temperature heat setting above the halfway
setting (60% heat).
(5) The pump will turn off at speeds above 48
Km/h (30 mph).
(6) The pump will turn off if the coolant temperature
rises above 110° C (230 ° F).

******************************
Even though not mentioned above, the aux electric coolant pump is also subject to Espar control 12V power is applied to Pin #6 to enable the Sprinter Espar D5 (pump energized).

I forgot to mention this.

I know that my Espar Booster heater has a 12 vdc supply that is not subject to the ATC Automatic Temperature Control push switch or the ignition key position. I figured that out during my heater testing. One of the times that I got the heater to run I noticed that it continued to run in a cool down or programmed shutdown cycle even after both the dash switch and the ignition key were off.

The programmed shutdown cycle is mentioned in the Espar controls description. So the Sprinter heater does have a 12 volt supply which allows the Espar module to operate the heater even when the Sprinter is not calling for it. By extension, I'm pretty certain that the Espar module keeps the electric coolant pump operating during that shutdown cycle to avoid overheating, but I didn't think to check for that at the time. In other words, the ESPAR module maintains the ability to control the Sprinter electric aux coolant pump. (Edit: Both the Sprinter and the Espar schematics support that idea.) The Sprinter Espar D5 does not care if the pump is running or not during the programmed cooldown/shutdown cycle. FWIW. vic
Due to some of the names and nomenclature used in the heater circuit information I feel that it is easy to get lost in the documentation. That MB labels the Espar Heater Unit a "module" is just one example.

Mercedes in their wisdom decided to combine circuits with only a couple little note symbols to differentiate the various options. What that does is split the Espar connections into different places depending upon which heater option you have. The schematics are even more complex than I imagined. :crazy:

It is extremely important to pay attention to the little symbols in the Sprinter schematics.
Cabin Heater Module = (Booster or Aux Heater)
REST System = (Stand alone engine heat scavaging)

Program Timer = (Timed or Programmed Aux Heater)
Except Program Timer = (Booster heater - engine running type)

AND

the actual pin numbers on the split up or sectioned dotted line box Espar Heater connector or "Cabin Heater Module (CHM)" as it is called in the schematic. Eg. - Note that the "Program Timer" Espar Pin #6 shows in both 8W-42-10 and in 8W-42-11. It is the same Pin #6, a duplication including the C204 Pin #7 above it.

I have added some notes to the schematics below. I know that the other related schematics (fan control and ATC module) will benefit from explanation notes too.

I'm not smart enough to create documents directly from the PDF manuals. Some of these are printed pages, hand written notes added, and scanned. If the picture detail is not good enough then you can refer to the ESPAR PDF for details.

The Sprinter VA Service Manual is available in the Database Section of the forum for the Service Manual 8w diagrams.

Please note that MB made no attempt to carry the Espar Heater connector wire colors out into the Sprinter.

NOTE:

The diode circuit modification will woork. There is a better circuit which I outline here.


REST/Booster Engine Pre-heat with DPDT Switch Modification

https://sprinter-source.com/forums/showthread.php?t=36797

My conclusion is that a 12 volt input to Pin #7 of the Sprinter Booster Heater will allow the heater to run as an engine pre-warmer with no other modifications needed one other minor mod . That is a blue wire with switch and diode for the Booster configuration and a yellow wire for the timed configuration. There should be enough info provided here to decide if that is correct. vic

EsparBoosterSwDiodeRunOrigSm.jpg

Note the pin numbers in 8W-42-11 (2 each pin #6 ) may appear to be incorrect for an "enable". That is because they are showing only a section of the connector. Some of the pins are shown in 8W-42-10.

Also note the "Fused Optional Equipment Relay Output" label on the Espar heater connections. It would more properly be named "Input" as opposed to "Output". The Espar heater is named the "Cabin Heater Module (CHM)" on the Sprinter schematic. That "Fused Optional Equipment Relay Output" is the electric coolant pump power "on" 12V input in the case of the Sprinter Booster installations.

I also believe that the OEM pump diode configuration isn't shown correctly. I can see no real purpose for the diode wired in as shown. My red line to the diode/pump node shows what I believe would be correct to prevent backfeed to the Sprinter electrics when the ESPAR control is calling for the pump to run. The diode *may* be is definitely related to keeping "pump power on" 12V from getting to Espar Pin #6 while the REST System is running the Aux Electric Coolant Pump.


8W42-09 wNotesRev2a.jpg

8W42-10 wNotesRev1.jpg

8W42-11 wNotesRev1.jpg

This is from the Espar PDF.

EsparMod25wNotes.jpg

*****************************


Here is one idea for a simple on-off switch to enable and run the Booster Heater configuration only without the engine operating. It requires only 2 wires to the dash for the switch and a fuse with diode and wire under the hood. This will only heat the engine and cabin for approx 30 minutes. It will not operate the cabin blower fan. I suspect that a another similar switch (or 1 ea. DPDT switch) could be used with the ATC/REST function to get the fan too. I haven't explored the circuit because I don't need that.

As an aside. I considered using a polarity blocking diode for the Pin #7 Enable feed. Normally that would work and reduce wire needed to the dash. From comments posted on some boating forums, I know that the Espar D5 computer module monitors supply voltage and will shut the heater off if it goes low. The voltage drop of the diode might be noticed. That drop isn't important for the blocking diode shown for the Electric Coolant (water) Pump, but it MAY matter for the supply voltage. Running one wire as opposed to running two wires up to the dash is no big deal anyway. No wires from dash to under hood are needed.

Based upon the comments in the method described in the next post below, it should be easy to locate and intercept the blue wire at the ATC Automatic Temperature Control in the dash to install the SPDT switch. The cigar lighter power socket can be used for the 12 volt supply as suggested also.

The fuse/diode and wire is fairly easily installed in the engine bay.

I tested my modification and it works even with the 10 amp Heater Control Power fuse removed from under the driver seat. The diode is to prevent/block the Pin #6voltage from backfeeding to other circuits during normal operation.

This updated circuit has some advantages. One of the things which I was not thrilled with about a "Constant Run" option was that the added Espar Booster Heater "Engine Off" SPDT switch could be bumped to the "On" position or forgotten. That would keep the diesel D5 heater operating forever. With the switch and diode circuit then the Espar D5 engine off operating time is limited to the 30 minute REST timed cycle.

From member comments the approx 30 minute run time should be enough to pre-heat the engine. If it is not enough in extremely low temperatures, then another REST cycle with the added SPDT switch enabled can be intiated to add another 30 minute time cycle.


Basic Circuit Description

The SPDT switch opens the blue wire from the ATC Automatic Temperature Control to stop any feedback of 12V to the ATC or other circuits. The constant 12V(+) (eg. - from the Power Outlet) feeds through the SPDT switch via the OEM blue wire to power Pin #7 "Heater On" or enable on the Espar heater. Note: The Espar will not actually start until it gets the "Pump Power Verify" signal to Pin #6 from the REST operation.

When the REST button is pushed the Aux Electric Coolant Pump is energized for a time of approx 30 minutes. The wire tapped off the DG/RD wire at the pump connector feeds 12V "Pump Power Verify" or 2nd Enable via the diode to Pin #6 of the Espar Heater. When the REST fan times out the "Pump Power Verify" 12V goes away and the Espar heater initiates a shutdown. When Pin #6 of the Espar is energized during any normal OEM Sprinter operation then the diode blocks any voltage from backfeeding to the Coolant Pump. (A diode in this configuration acts like a check valve in a water system.)

This circuit will not adversly affect any other OEM Sprinter circuit operations. The REST System will not turn on the Espar heater until the SPDT switch is "On" to enable Pin #7.

Using the SPDT switch assures no backfeed of power to the ATC or any other circuits. I wasn't able to determine for certain whether backfeeding of voltage to the ATC would have any adverse affects or not. The safe route is to use the SPDT switch.

It *may* be OK to just use a SPST switch and feed the Blue Pin #7 wire 12 volts directly without worrying about feedback. That is ok to do. There is no backfeed problems with the ATC and the blue wire.


Some additional information is in this thread.

https://sprinter-source.com/forums/showthread.php?p=273061#post273061

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

Some 2004 Espar Heater Notes
https://sprinter-source.com/forums/showthread.php?t=30384

Remove Espar Heater from T1N
https://sprinter-source.com/forums/showthread.php?t=30427

General Espar Heater Wiring Information
https://sprinter-source.com/forums/showthread.php?t=30191

Cabin Fan Resistor Circuits
https://sprinter-source.com/forums/showthread.php?t=30286

T1N Booster Heater Wireless Control
https://sprinter-source.com/forums/showthread.php?t=30512
 
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220629

Well-known member
Below is a method of getting the heater with a 7 day timer to work. Based upon my research I don't agree at all with some of the OEM and Espar circuit logic as explained in his Write-up (blue wire and use of D+ as an "inhibit"), but you can't argue with success as to his method working.

I still stand behind my interpretation of the OEM Sprinter and Espar documents in my post above as to the heater circuit operation. The schematics have their flaws, but they aren't completely wrong as to the application and basic wiring of the major components.

Thanks goes to jimwhs and prsiii. :thumbup:

After reading and searching around the forum last year, I found that back in 2011, a guy (user name prsiii) posted what I thought was a elegant solution. And it works great. The wiring was rather simple, and as he said, is done entirely inside the cab, no adding wires between the cab and the engine compartment. I don't understand why no one else ever really picked up on it. Here is what he described, with a few little additions provided by me to clarify some details. Note however that I added just 1 simple switch to turn on the Espar along with the pump. It took me a few hours to do this to my 2005 2500, and then I added a small additional heat exchanger and fans near the back of the van to heat the "living space"

Posted by prsiii, on 6/17/2011
Bent on installing a 7-day and a home made 'controller', today was an 'interesting' afternoon...in the fortune cookie sense. My first discovery was not only are the fuse locations in the service manual 'wishful thinking' but the MB schematics are not at all accurate as they relate to an MB chassis for a Winnebago Class C. I do have this to say after getting everything working like a champ: The
'controller' circuits published previously are gross overkill to accomplish the job: I did my mod with only one relay, a couple of 3amp diodes, and NO wires going through the firewall to the heater.

Current measurements for the record books from my rig:
Timer idle and heater bias (timer backlight is off) = 55mA
Water pump, system hot = 650mA
Fan on low = 4.6A (had to test this by pulling the 30A fan fuse, I won't be using that dash fan for sure! My new exchanger draws 1.2A on high)
Have not taken current readings on the heater, assuming 60W/5A on high per the manual.

Noteworthy: The most annoying and difficult aspect of the published control shows a pair of wires going to the Espar. The odd thing is what this wire does: In the manual, it is called 'Terminal 15' and in another place it is called 'D+', what it really is connected to is the D+ (engine is running) bus. That's right, it tells the heater when the keys are in the ignition and the engine is running. This is what prevents the heater from running by itself. [If "inhibit" is intended then the blue statement is incorrect. There is simply no power for the Espar Pin #7 (enable or run) from the D+ until the key is on.] In the service manual, this signal is run through Fuse Block 3 #7 (10amp.) ky sprinter has no Fuse Block 3, but on the chart behind the panel there is a 'Boost Heater Terminal 15' fuse in Block 2 #6 (10amp.)

This is what you do:
1) Go to the auto parts store and get one of those ATC fuse holders with pigtail wires, and two splice in terminal blocks.
2) Remove the drivers seat (4 allen key bolts) and locate the 'Boost Heater Main Fuse' (25amp.)
3) Remove both boost heater fuses.
4) Behind the fuse block, locate the small-ish wires coming from both fuses, usually they are going into the lower terminal (closest to the road.)
5) Splice the new fuse holder to the wires coming from both fuses
6) Install the 10amp fuse into the new fuse holder
7) Re-install the 25amp fuse
...now the heater will think it's okay to run when commanded, as 12v is on both the power and 'Terminal 15.' Note there is no messing
under the hood, running wires, etc. Simple, eh?

To make the heater and water pump run, now all you need is to inject 12V into the appropriate wires in the ATC (this time ATC stands for the dash climate control unit) harness: Green/Red wire (fires up the pump) and Blue wire (fires up the heater.) The pump should run from a relay because it draws about an amp at startup, but drops to 600-700ma during normal operation. The blue wire is a logic signal, it will operate with only 15mA of current. I drove the blue wire from a diode from the same signal that drives the relay. That way the signals are independent when all is off. The dash blower will only be run by the REST function (30min max) to ensure I never drain the battery. My secondary heat exchanger will run off the coach batteries.

For me, I wired the 7day timer so that both +12 and ACC go to the battery (disables the 2hr runtime limit) and that kicks the blue wire and the relay to run the water pump. Next project is the plumbing to the coach heat exchanger, and I hate plumbing;)

And point of clarification of exactly what I did in the dash, I took power from the cigarette lighter to my new switch, connecting the switched 12v to 2 2A diodes that connected directly to the Green/Red and to the Blue wires on the ATC. I didn't see the need to add a relay for a signal that has a peak current draw of 1 amp.
 
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220629

Well-known member
A Quick Test for the AUX HEATER TIMED UNIT Espar Operation

(Note: This test doesn't work with the Booster Heater configuration. You will need to find the blue wire on the dash ATC module and jump that to 12V.)

Thanks goes to Autostaretx Dick. :thumbup:
vic

On a related note: i have the full T1N Aux heater with the 7-day timer.
Many years ago, my timer stopped working for a week (no clock display, no buttons worked, pulling it out and kicking it around didn't help).
Then it "fixed itself" and worked until this winter.
We're planning for a Boxing Day trip to Canada, so i figured i'd better come up with a work-around.

Thanks to this discussion, i thought i'd try simply jumpering a wire between the timer's connector's pins 2 and 11 (yellow to red).
(with the timer removed for access to the connector)

It worked. Even with the engine off, the Aux Heater ran through its start-up routine and fired up.
The cabin air circulation fan merrily blew.
Pulling the jumper caused the Aux Heater to go through its usual shut-down procedure (kill fuel and flame, continue to pump air and water for 3 minutes).

In the "why a D+ ?" matter, the Boost and Aux (without timer) heaters will only work with the engine running.
Monitoring D+ is one simple way to tell the engine status.
The Aux Heater with the 7-day timer doesn't care about the engine running (D+) status... it's willing to run either way.

--dick
 
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autostaretx

Erratic Member
Perhaps the Circulation Pump Diode is in there to prevent back-EMF if the pump ends up acting as a generator?
If the coolant is circulating (due to engine pump) then the circ pump's vanes are probably spinning in the flow.
Depending upon the pump design, it could end up acting as a DC generator.
By providing the diode, MB is allowing themselves to substitute pump technology without system re-design.

added: Whoops... is that Red Line correction/change you added how your Sprinter is actually wired?
Then the diode would be preventing the Red Line "run the pump" voltage from going back through the relay contacts to Splices
S206 and S223 (depending upon relay state).
(Ahh: 4th re-reading re-found your " My red line to the diode/pump node shows what I believe would be correct to prevent backfeed" comment)

--dick
 
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220629

Well-known member
Perhaps the Circulation Pump Diode is in there to prevent back-EMF if the pump ends up acting as a generator?
If the coolant is circulating (due to engine pump) then the circ pump's vanes are probably spinning in the flow.
Depending upon the pump design, it could end up acting as a DC generator.
By providing the diode, MB is allowing themselves to substitute pump technology without system re-design.
Very good thinking. :thumbup:

Maybe, but they don't show a diode on the REST pump configuration shown in 8W-42-9. So if you order the REST option with the Sprinter, but not the Booster Heater then you don't get a diode. Wouldn't your "gereator" idea apply to REST also? :idunno:

2014/01/01 Edit: I *think* that I have the answer.

The diode most likely prevents voltage from going to the Pin #6 "Pump Energized Verify" on the Booster Heater. With the REST only option then MB had no need to block the voltage becuase no diesel fired heater exists.


added: Whoops... is that Red Line correction/change you added how your Sprinter is actually wired?
Then the diode would be preventing the Red Line "run the pump" voltage from going back through the relay contacts to Splices
S206 and S223 (depending upon relay state).
--dick
The red line change was wrong and has been deleted.


NAH-H-H!! Not actual wiring.

I ain't even actually gotten my Booster Pump to run reliably yet. I'm just going by what *I think* I've learned.

Thanks for the input. vic
 
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220629

Well-known member
Update
REST/Booster Engine Pre-heat with DPDT Switch Modification

My original circuit using a switch and a diode for REST engine pre-heat works, but it has some flaws in that it can backfeed 12 vdc into some other circuits connected to Splice #362. For a basic optioned Sprinter like mine that is not a problem. For Sprinters which have things tagged on to the Optional Equipment Relay it can have some negative effect. (Not necessarily serious, just a nuisance.)

Realizing that, I looked for another option. After a couple different solutions I developed a circuit that uses a common Double Pole Double Throw DPDT switch. This new circuit prevents any 12 vdc backfeeds and should also address the ABS module pre-start check glitch.

Most of the connections are found in the dash area on the ATC Module. I know that running a 2 conductor cable from the DPDT dash switch to the BK/BL/DG wire Espar Pin #6 at the Booster will work. That BK/BL/DG wire may be available in the area of the dash to cut and connect. Using the documentation that I have available to me I was not able to determine if that is a practical method or not.

With the DPDT switch in "Normal" position (as shown) the REST and Booster Heater function per OEM design. With the DPDT switch in "Pre-heat" position REST powers up the DG/RD wire Circulation Pump which also enables the Espar heater. This allows approximately 30 minutes of pre-heat operation until REST times out.

Here is the basic circuit shown on the Booster Heater Diagram.

10.3.3 BoosterPreHeatRESTrev2.jpg

Presently my switch and diode arrangement does what I need for my engine pre-heating. I don't plan to change over to the new design. That said, the newer DPDT switch circuit modification is the better choice.



If anyone has questions please start another thread. That will allow me to move information to here rather than having this thread go too far off topic. vic

P.S. - Some PM's with Mortarsprayer got me back to thinking about this modification.
 
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autostaretx

Erratic Member
Just for the record, here's the annotated wire-side of my Aux Heat Timer connector:



--dick
p.s. pin 1's wire has a grey body, a narrow dark green stripe running along the wire (hiding on the other side of the wire in the photo), and the obvious rings of red.
Likewise, pin 10's wire has a black body color, a narrow blue stripe running along the wire, obvious green rings.
 
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220629

Well-known member
Just for the record, here's the annotated wire-side of my Aux Heat Timer connector:

...
Dick,
Thanks for the help with this additional information. Great picture.

AuxHeatTimerConn.jpg

Some General Information

This is an attempt to avoid confusion..

The heater unit Dick is referring to is a "Program Timer" type heater or Aux Heater with dash timer control, not the "Except Program Timer" more basic Booster Heater which my SPDT switch information applies to.

It is very important to be certain to stay with the proper heater style when checking on the circuits. The basic Espar Heater units are the same, but the control design which MB applies is completely different. It is easy for the schematics to trip a person up. (At least it was for me. :bash: )

vic
 
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