REST/Booster Engine Pre-heat with DPDT Switch Modification

tinman

Well-known member
Than you Vic,
I think this will help many people that would like to run the booster heater with the key off.

Does anyone have a Mercedes part number for a DPDT switch that would snap nicely into the dash?

Best regards,
Nolan
How about 5120484AA? It's a DPDT front and rear fog light switch.

Andy
 

Aqua Puttana

Poly - Thread Finder
Hi, I have a 2006 cargo with an Aux heater but no timer panel, would this wiring setup enable the heater ?
Good question.

First. Do you have the Aux Heater option for certain and not a Booster Heater? I recall that the MB Aux Heater option would run 2 hours without the engine running, but my efforts have not included anything other than the Booster Heater that is in my van so don't take that as Gospel.

The documentation mentions Program Timer, Except Program Timer, and a few other specific note symbols in various places.

Your Data Card will specify what heater option was installed by the factory.

All that said, the circuit as shown is fairly basic so it should work with any MB OEM Espar heater.

How about 5120484AA? It's a DPDT front and rear fog light switch.

Andy
That sounds like a very good possibility as long as it is not momentary contact. Great find.

vic
 

Aqua Puttana

Poly - Thread Finder
Overthinking. With the way the guy set it up, the REST would control the pump, so he only needs to feed power to the blue wire. But this needs to be controlled by the REST so it will shut off on it's own. So you could pull power FROM the Green/Red to feed the blue.
My problem about not seeing those modifications on a schematic is any back feeds. That is also a possibility/problem with my original fused diode and switch circuit.

The 10 amp Booster Heater fuse (position #7 for my van) is gang fed with other fuses. If not addressed, that provides a feedback path through the 10 amp fuse to the other fuse circuits.

Back feeds can have different consequences depending upon the OEM options ordered with the van. It's probably best to avoid them unless you know what they really will power up. Even with a circuit being displayed on the MB schematics the many circuit variations would still leave some doubt in my mind as to the accuracy.

I have yet to find the wire colors and circuit which, per inspection and testing, is actually in my van. I do know that the backfeed via the blue wire to ATC pin C1-10 has no problem. That said, the DPDT switch is in the circuit I designed to prevent the blue wire from ending up common with other wires/circuits when not in REST Pre-heat mode.

vic
 
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Aqua Puttana

Poly - Thread Finder
Hi, what is the difference between a Booster Heater and an Auxiliary heater ?
Here's some information, but please take any further non-pre-heat questions over to one of those threads.

As always, the original thread/post can be accessed by clicking on the blue arrow icon within any quote box.

Auxiliary, Boost Heater and REST Description of Operation

Search: Auxiliary Auxilliary Aux Booster Espar Heater REST function operation

As I was originally confused about the Booster Heater, Auxiliary Heater, and REST functions. I'll outline what I THINK I know for those who may not be up to speed.

The circulation pump on my 2004 is mounted on the firewall to the left of the battery above the EGR. One hose goes to the EGR valve. The other from the Booster Heater via a steel coolant line. I'm certain that varies with year or if you don't have a booster heater (Edit: REALLY???....:doh: should be and when you don't have a booster heater).

With my 2004 the coolant circulation pump runs for a second or so after the engine is turned off. Mine has a bit of a noticeable hum. It seems normal as there has been no problems other than the brushes wearing out.

Often the pump motor brushes can be replaced DIY to avoid the purchase of a $100.00+ pump assembly. Links:
https://sprinter-source.com/forums/showpost.php?p=74365&postcount=88
https://sprinter-source.com/forums/showpost.php?p=74549&postcount=4
https://sprinter-source.com/forums/showpost.php?p=74569&postcount=9

Apparently there is also a VW -Bosch(?)- branded circulation pump that is identical except for the electrical connector for a bit less cost.


The REST function is a timed operation of the electric circulation pump which scavenges heat from the engine by running the circulation pump and the fan after the engine is shut down. On mine the blower fan runs at low speed with REST on. The rest function and LED cycle off if the engine is running. Per MB you can extract heat for about 30 minutes. The REST function does not operate the Booster Heater (unless modified).

The Booster Heater function is a diesel fired heater located below the battery in the T1N Sprinters. It is most easily accessed by removing the grill and headlight pod. The Booster Heater operates with the engine running to add heat to the heater core for the cabin heater. The OEM Booster Heater will not operate with the engine off unless the controls are modified for constant operation. The engine coolant pump will circulate coolant through the booster heater at low vehicle speed and engine RPM. The electric circulating pump on the firewall is not needed for the Booster Heater to operate when the engine is running under specific operating conditions (coolant temp, vehicle speed, +).

Edit: The Booster Heater can be wired to run with the engine off.

REST/Booster Engine Pre-heat with DPDT Switch Modification

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

The OEM Auxiliary Heater is mounted in the same location as the Booster Heater in the T1N Sprinters. The Auxiliary Heater has OEM controls which allow the Auxiliary Heater to be operated when the engine is not running. It includes additional timers and controls not included with the OEM Booster Heater. The Aux Heater can be used to pre-warm the engine before starting. It will also perform the same as a Booster Heater with the engine running.

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

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

2010/12/06 edit: A more formal description. Thanks goes to bc339 Bruce.
***
To add to Vic's explanation, trying to prevent further confusion, I copied this description in the service manual for the supplemental heater:

Vehicles equipped with the optional diesel engine are also equipped with a supplemental heater unit. This unit is mounted under the vehicle and operates similar to an oil fired furnace. The heater burns small amounts of fuel to provide additional heat to the coolant. Coolant is routed from the engine, to the supplemental heater, and then to the front heater core. This provides additional heat to the passenger compartment. The system is interfaced to the vehicles on-board computer systems and DRBIIIt diagnostics. The supplemental heater unit has an electronic control module that monitors the heat output of the heater. The heater operates at full load (5 kW), half load or idle mode (no additional heat) depending on coolant temperature.
OPERATION
The supplemental heater is activated via the temperature control on the heater-A/C control. The heater is activated when the temperature control is set to/or above the upper set point. The supplemental heater can operate in a full or partial load range as well as an idle mode, all dependent on the engine coolant temperature. The heater unit will also turn off if the temperature control is set to less than the lower set point. The supplemental heater can take up to three minutes to completely shut down when either the heater temperature is set below the lower set point or the vehicle ignition is turned off. The supplemental heater only operates when the engine is running, the mileage exceeds 8 kilometer (5 mph) and the fuel tank volume exceeds 1/8 of a tank. The heater should start if the coolant temperature is below 40° C
(104° F).

When I was troubleshooting my coolant pump failure last year, this explanation helped me figure out why my Heater Booster would work, but not the Aux Heater.
My Sprinter is configured with the supplemental heater located behind the left headlight - controlled by the Heater Booster Switch (below the A/C switch), REST feature and the Auxillary Heater, controlled by the 7 day timer.
The Heater Booster and Auxillary Heater use the same heater unit, but are not controlled or operate the same. The REST feature is totally separate.

Bruce
2010/05/09 edit:
Both the REST and Booster Heater are controlled by pressing the round knob like segments on the right of the dash in NAFTA Sprinters. An LED will light for the function that is enabled.

2010/02/07 edit:
A recent thread about the booster heater. "Works while idling in 'Park' on my 2006 2500. Booster fires up almost immediately after starting the engine." Matt/Smoky pond
https://sprinter-source.com/forums/showthread.php?t=9869
****
Additional info from Bill Drescher "houndsofheaven" on Sprintervan:
correct - my diagnosis of an inop coolant pump was made because the Esapar worked fine with the engine running [Add - The main belt driven coolant pump was operating. - vic], but shut off quickly when the engine was not running (Auxiliary Heater)


Another comment added by Bill:
and can be used to keep the engine/cab warm when you go into a store. It is one of life's great pleasures !
***
Some additional comments 2010/08/16. Thanks goes to Douglas.
https://sprinter-source.com/forums/showthread.php?p=102676#post102676

Some heaters come with a duct for hot/warm air. I have a dsl fired auxilary heater for my 2005. It is an option I sspecial ordered. It is mounted behind the left headlite. My heater control is in the lower center of the dash panel. I push the button with the red squiggly lines, holding it down untill I hear the to dosing pump click. Dosing is a fancy, expensive way to say fuel pump. If the driver's door is open, you can hear the aux heater come on, it sounds like a jet engine. The exhaust pipe exits by the left front wheel. The heater heats the engine coolant, which is circulated by a 12V pump. There is a thermostat someplace. If you have a dsl fired heater, no matter the location, run it for 10 minutes a month. The DAD is thought to diagnose heater problems.

Some heaters are mounted in the cargo/passenger area. In my 2003, we added a heater there. It is dsl fired, thermostatically controlled and forces hot air into the rear compartment. Some vans may have had that heater installed at the factory.

There is also another heater, the REST. It uses [scavenges] residual heat from the engine to keep the cab warm. Push the lower buttom to operate the REST when leaving the van for a few minutes. It will run w/o hte key, for about 20 minutes, at least in my van.

Heaters are another mystery in our vans. No one, except Dr A understands all of the options in the Sprinter. There are rumors MB calls him for help.
20100918 edit - A recent thread which includes pictures of the various control panels for heaters. Rick found someone had replaced his Aux Heater control panel with an incorrect unit that didn't have the wavy lines. Thanks goes to Rock Auto and Ricksan.

Note: This is an unusual situation. A booster heater (basically runs when the engine is running) can be changed to an aux heater (will run as set by the controls), but it is not as easy as just changing the control panel over. A search will provide more information on the steps necessary.

New owner 2005 3500 158
https://sprinter-source.com/forums/showthread.php?t=12704

2010/10/24 edit: A recent thread over at Yahoo sprintervan which has some good information from members.
http://autos.groups.yahoo.com/group/sprintervan/message/57741

2010/12/28 edit:
That list of options left out the T1N's rear cabin heat exchanger option: H13.

More info about the rear heater thanks to autostaretx (Dick) is in this post.

https://sprinter-source.com/forums/showpost.php?p=118581&postcount=7

2010/11/04 edit: A thread about the NCV3 heaters complete with pics of the controls. Thanks goes to all contributors.

NCV3 Heater Systems
https://sprinter-source.com/forums/showthread.php?p=112470#post112470

Please feel free to correct any errors or add information. I hope this does some good. AP/vic
 
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ECU

Well-known member
I dug in and got my espar firing up. I jumped the fuse under the seat to hot all the time. That is the Fuse #7 which is really Fuse #13 on mine.
Then in the dash, I pulled out the switch console and found the blue wire. This fired up the espar and with the REST on, it heated fine.
Then I tapped in to the Dark Green/Red wire. This is 8w-42-9, lower right. It feeds the pump and turns on and off with REST. I used this as the source of 12v and had a working system while off.
I tried to turn on the engine and the dark green/red wire becomes 12v again and will fire the espar. Of course this is not what I want. But it is a start.
By the fact that I get 12 volts, I'm guessing that there is no diode in the system. Either that or this blue wire is the source for all pump operations.
My solution will be a relay. Use the ignition power to feed the coil of a relay. The power from my dash switch combining the green/red wire to the blue wire will run through the NC part of the relay. That way the switch will only control the espar while the ignition is off.

This confirms the description by prsiii.
 

Aqua Puttana

Poly - Thread Finder
...
By the fact that I get 12 volts, I'm guessing that there is no diode in the system. Either that or this blue wire is the source for all pump operations.
...
I agree with the no diode.

The blue wire is just enable in the OEM Heater Booster Module configuration and has nothing at all to do with the pump. Unless somehow modified from the original configuration, with the OEM Booster Heater option the pump is solely controlled by the ATC module. That is not true with Program Timer heater options.

vic
 
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cahaak

New member
I know that this is a little of topic here, but the original mod - getting the ESPAR to run from a switch is simple and there are no issues what so ever with this set up as the mod is completely disconnected from the van when it is off. It is 4 relays and then either a switch or the 7 day timer. Most of the work can be done out of the van and then there is one connection(two wires) to the ESPAR itself. I did my mod almost 5 years ago and we use this almost daily in the winter - along with REST and the regular booster while running.

The sad thing to me is that Mercedes could have / should have enabled this right from the start especially for colder climate vans as there is no additional hardware needed to make this happen, everything is in place. If they were really thinking of the customer, they would have made it so.

Chris
 

Aqua Puttana

Poly - Thread Finder
I know that this is a little of topic here, but the original mod - getting the ESPAR to run from a switch is simple and there are no issues what so ever with this set up as the mod is completely disconnected from the van when it is off. It is 4 relays and then either a switch or the 7 day timer. Most of the work can be done out of the van and then there is one connection(two wires) to the ESPAR itself. I did my mod almost 5 years ago and we use this almost daily in the winter - along with REST and the regular booster while running.

The sad thing to me is that Mercedes could have / should have enabled this right from the start especially for colder climate vans as there is no additional hardware needed to make this happen, everything is in place. If they were really thinking of the customer, they would have made it so.

Chris
For basic engine pre-heating I don't see any great advantage with multiple relays and timing over the single DPDT switch which started this thread.

The circuit that you are suggesting is far from a simple and cheap installation. Well, I guess it keeps you from needing to go out and hit two switches. To pre-heat my engine I just go out and hit my switch, push REST and go back in for coffee. You don't need to be exact about starting the engine immediately following the REST/Pre-heat time out. After the REST/Pre-heat shuts off the engine will hold the heat for at least another 1/2 hour, probably longer.

If anyone wants to have more control than a simple 1/2 hour REST/Pre-heat switch then I suggest that this is not the place for further discussion. There are other threads which already discuss that.

I'm certain that one reason MB doesn't offer the Boost Pre-heat is that they already provide that feature with the Aux heater (Program Timer) option which is complete with OEM required safety and vehicle standard approvals. Everyone should be aware that none of the DIY designed heater control changes/options have any approval. That includes my design also.

:cheers: vic
 
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ECU

Well-known member
I finished the wiring on my project, as described earlier. I just used those add on jumper fuse thingies to wire the espar from my aux batteries.
Fired it up. Usually this must happen when I'm driving and don't notice. But it smoked up quite a bit for the first few minutes, maybe five minutes. Then it simmered down to clear the air. Then it ran for quite a while, maybe another ten minutes. I noticed that the water temp was at 184F (84C). The espar never stopped, yet I think the water was warm enough and it was heating the cabin nicely.

Should the espar shut down when it gets to temp?

One other item of note. I noticed that when the key is turned to the first position, the radio comes on but the REST does not shut off. I didn't get around to testing this idea but here goes. What if the Fuse #7 wire were hot when the key is in this position? No extra wiring there! Simply put +12 to that blue wire under the dash controls and you'd have heat only when the key is on.
 
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Aqua Puttana

Poly - Thread Finder
...

Should the espar shut down when it gets to temp?

...
Yes. There is definitely an Espar operating high limit and a safety high limit. I recall 167F or maybe 176F coolant temp for operating on the MB units. (It is different for some Espar units.) The MB Sprinter Espar temperature info is called out in Sprinter-source posts.

When feeding 12 volts without isolation of some type, backfeeds to the ATC or other circuits can cause strange problems.

vic
 

ECU

Well-known member
So, where did we go wrong? From what I've seen, there is a temperature sensor internal to the espar. could the control be external?
I can see that the heater might be in control of the espar and that the hot 12v to the pin would bypass any on/off functions. But quite a few people have done this mod without reporting if it runs constantly or on/off with temp.
 
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Cheyenne

UK 2004 T1N 313CDi
Yes. There is definitely an Espar operating high limit and a safety high limit. I recall 167F or maybe 176F coolant temp for operating on the MB units. (It is different for some Espar units.) The MB Sprinter Espar temperature info is called out in Sprinter-source posts.

When feeding 12 volts without isolation of some type, backfeeds to the ATC or other circuits can cause strange problems.

vic
From the Espar D5W operating instructions there is a temperature sensor in the water jacket of the espar and this operates the espar as follows..

Switching temperatures
High — Low 80 °C
Low — Off 85 °C
Off — On 75 °C
Low — High 75 °C

As 80 °C is 176 °F this is the temp you mentioned above so is where the espar drops from high output to low. And at 185 °F it should turn off.

There is also an overtemp shutoff if all else fails and this operates at 125 °C (257 °F) and may cause a total lockout of the espar.

Hope this helps,
Keith.

Edit to add, if the pump is running then coolant entering the espar should keep the temperature low enough to keep the espar running when the engine is off.
Also control is internal to the espar, ie not controlled by MB electronics.
 
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ECU

Well-known member
Ok. Does it keep spinning, noise making? That could be why it quit smoking?
 

Cheyenne

UK 2004 T1N 313CDi
When the temp reaches 85 °C and it drops from high to low power this is a drop from 5 kW to 2.2 kW of heat output.
This drop in power will probably be at the time you saw the unit stop smoking as it will have been as a result of a reduction in fuelling (0.62 to 0.27 litre/hour). You may also hear the internal fan slowing but I can't remember for certain.

Do you have copies of espar manuals? I have gathered electronic copies of several over the years and they are really useful.

Keith.
 

ECU

Well-known member
I think I have a couple of files. RTFM is always a good answer.
Now, with good weather, I may not need to preheat.
I'll be on the lookout for a cabin thermostat next.
 

Aqua Puttana

Poly - Thread Finder
From the Espar D5W operating instructions there is a temperature sensor in the water jacket of the espar and this operates the espar as follows..

Switching temperatures
High — Low 80 °C
Low — Off 85 °C
Off — On 75 °C
Low — High 75 °C

As 80 °C is 176 °F this is the temp you mentioned above so is where the espar drops from high output to low. And at 185 °F it should turn off.

There is also an overtemp shutoff if all else fails and this operates at 125 °C (257 °F) and may cause a total lockout of the espar.

Hope this helps,
Keith.

Edit to add, if the pump is running then coolant entering the espar should keep the temperature low enough to keep the espar running when the engine is off.
Also [temperature control and high limit] is internal to the espar, ie not controlled by MB electronics. [For the Booster Heater option in OEM configuration the pump is controlled solely by the ATC.]
Good information. I added a bit of clarification in blue.

.... But it smoked up quite a bit for the first few minutes, maybe five minutes. Then it simmered down to clear the air.
What color smoke? It really shouldn't smoke except for a wisp of white smoke during start sequence. That said, billowing white smoke could be left over fuel in the muffler from previous failed starts. After the heater gets to properly operating the higher exhaust temperatures evaporate the raw fuel out of the muffler. Black smoke is incomplete combustion.

.... Then it ran for quite a while, maybe another ten minutes. I noticed that the water temp was at 184F (84C). The espar never stopped, yet I think the water was warm enough and it was heating the cabin nicely.
I missed what you intended.

My Booster Heater will run at 1/2 power for quite some time without shutting off completely.

I still believe that MB requested the operating limit to 1/2 power to be a little lower than most standard Espar heaters. I recall that from a MB specific document.

vic
 

ECU

Well-known member
Good information. I added a bit of clarification in blue.


What color smoke? It really shouldn't smoke except for a wisp of white smoke during start sequence. That said, billowing white smoke could be left over fuel in the muffler from previous failed starts. After the heater gets to properly operating the higher exhaust temperatures evaporate the raw fuel out of the muffler. Black smoke is incomplete combustion.


I missed what you intended.

My Booster Heater will run at 1/2 power for quite some time without shutting off completely.

I still believe that MB requested the operating limit to 1/2 power to be a little lower than most standard Espar heaters. I recall that from a MB specific document.

vic
The smoke was white. It was kind of funny, I had the driver's door open and it started to fill the cab. The whisp was probably the size of three sprinters. Totally engulfing it when viewed from the side. Of course that was three short sprinters.
I'll fire it up again and see how it goes. could have been left over.

Yes, I expected it to shut clear off and on for temp control. So now I feel better about that.
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
A few notes which may help folks as I'm currently engulfed in this project:

1. I found an Espar which would start, shut off, start, shut off. This process put diesel into the exhaust system. :hmmm:
2. I started to disassemble the 'working' (trying to start but would not go into 'jet' mode) espar and striped the linchpin bolt only to completely rip the head of it off after I drilled it
3. Following building a Frankenstein D5WZ out of my non working Espar (throws weird codes all over the place) with the one which would at least go into a start mode, I had a WORKING (start, little white smoke, jet-mode, lots of heat coming out of the exhaust, eventually a 007-style smoke screen coming out the exhaust) Espar!!!!!
4. The first thing I noticed was enough smoke (once the exhaust system got hot after a few minutes) for the fire look-out on top of the mountain next to my house to get concerned. This was 100% due to the exhaust system being filled with diesel due to the 'working' (trying to start but would not go into 'jet' mode) espar not burning the Diesel in the start/stop processes it went through
5. Now that I finally got a working Espar, time to trick the D+ Dynamo (Terminal 15) pin (pin # (chamber #) 7) into thinking the engine is on... Guess what (I'm now seeing hints of this in other posts), the fuse legend on the cover of the fuse box under the seat is NOT ACCURATE. I jumped the #3 (Heater booster #3, 25A) with the fuse #6 (Heater booster, Terminal 15, 10A) but the #6 was actually for the driver side power window which was called out as #7 fuse on the legend.

Re #5, are you kidding me Mercedes?!?!?! Was this some sick joke to play on us silly Americans buying your amazing German engineering? I have to say I love my van but your attention to documentation detail and wiring is for the birds. Add that to your sensors taking a dump and then your ECU telling diagnostic tools that it's something different from what sensor is acting up and you've got some pissed off customers. Go talk to the Japanese and figure out your wiring, sensors, documentation and perhaps you'd have a vehicle worth paying all the $$$ you ask for. Okay, I'll get off my soap box.

Anyhow, I'm now going to test every single wire moving forward before I do anything. I'm glad I didn't blow myself or my vehicle up!

Chris
 

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