Question for Trek

nabsim

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We had some discussions six months or so back after I discovered I had a pre-heater fitted to my Sprinter. Currently I have to start my engine to run the pre-heater but I have the instructions for changing that so it can run independently.

Just to recap this would be useful to me as I have a calorific working of engine coolant for hot water. I was thinking of digging the instruction out last weekend and getting it changed over when I realised the water pump wouldn’t run if the engine wasn’t running. Is the fact of the water being heated enough to circulate it on its own or would I need to do additional work?

i am directing this at you as I think you said you had changed a pre-heater to run independently. :)
 
Some sprinters with the auxiliary heater also have a small electric water pump in the coolant system


Not sure on your year if you have a dash button labelled REST This is normally used on a cold day when you arrive somewhere with a hot engine and want to keep the interior warm using the remaining heat from the engine to keep the interior warm for extra 20 or so minutes

If you have this button then you probably already have the electric pump
 
If your heater only works when engine running then its an AUXILIARY heater

If it works independently of engine running then its the PRE heater and will need a pump if there is not this small electric pump I have mentioned

Follow both hoses up from the diesel heater up to the engine block and see if there is a pump As shown in my photoD7101410-60BD-4540-84FE-A63EF67F82D7.jpeg
 
I have the REST switch on the dash, tracing the pipes round I can see this, does it look like it may be the extra pump?
118674CB-D424-4620-ACF3-CFFA797FBC7B.jpeg
 
YES! thats the electric water pump for the REST facility

Next time you stop with a hot engine turn off ignition get someone to press the REST button while you are holding the pump and hopefully you will feel it running when that button is pressed

When you convert from AUXILIARY to PRE HEATER then this pump will be used to circulate the heated water from diesel heater around the heater matrix and engine block
 
YES! thats the electric water pump for the REST facility

Next time you stop with a hot engine turn off ignition get someone to press the REST button while you are holding the pump and hopefully you will feel it running when that button is pressed

When you convert from AUXILIARY to PRE HEATER then this pump will be used to circulate the heated water from diesel heater around the heater matrix and engine block
Brilliant! Thank you for the info :)
 
Well worth modifying in my opinion, its great warming up the engine and the cab on a cold day , means the windscreen defrosts as well if heater controls set to windscreen position and on hot with fan set to on

Just remember to turn the pre heater on 20 or so mins before you are ready to leave
 
The main reason I am thinking of doing this is to provide hot water in the van. My van starts much better with a cold (Spring, Summer and Autumn cold) engine than with a warm one. I believe this is the camshaft sensor at the back of the engine causing it. I intend asking the garage to change it if they agree it may be the cause when it eventually gets it’s service. Not been home to get it done though yet.
I am thinking of taking power from the habitation batteries when I do it as well so as to limit drain on starter battery but I dont want to bodge original cabling so may leave as is. I carry a generator now so it shouldn’t be a problem if it pull it down once in a while. Would you leave on starter or change while modifying anyway?
 
I think I would be inclined to leave the supply battery as is until you have used it a few times as you intend then decide

Mine is on engine battery but i dont generally use it other than a preheater

Though it gives me options to heat the van with diesel using this via the ALDE heatexchanger and vis versa I could warm engine via Alde on gas or hookup
 
Thanks again Trek much appreciated ?
 
Have been reading lots of stuff on the USA Sprinter forums about this and ended up thoroughly confused. Let me recap what I know for sure so far then I have a question at the end.

With ignition off I can switch the Rest button on and get air coming out of the vents and water pump runs.
With ignition off I can also switch the centre button under the Rest and run air to the back of the van which passes through a heat exchanger for the calorifier.
If engine has been running the air is hot, if not the air is cold for both these options (obvious I know but want it clear).
I then have two additional switches, one with wavy lines going up and another with wavy lines going down. With ignition on switching the one with wavy lines going up starts the Eberspacher water heater. Can’t recall what the wavy lines going down does at the moment but don’t think it relevant to this.

After reading all the info on the US site I keep coming back to just needing to run a permanent live instead of the d+ to the Switch with the wavy lines going up to start the water heater with ignition off. So that is my question to Trek, is it that simple?
 
When my sprinter chassis was built it had a single position button with wavy lines to contol (on/off) the auxiliary diesel heater which would only work with the engine running

When i converted this to a prewarmer as well (works when engine off) as well as the auxiliary heater function ( works only with engine running) i had to change the single switch to a double one

One direction was aux other was pre heat


If yours is two position switch it suggests you may already have the pre heater ?
 
Should work with engine running when pressing the one button , and with engine off when pressing the other side of switch
 
It’s just on/off. I don’t use it to warm the engine though as I didn’t know I had it. I would be happy to have it just run when I want (ignition off).

Is this why they are saying fit a switch on the US forum? I couldn’t work out if they were saying that because they didn’t have the one with the wavy lines, they quoted a MB part code for the switch I have at one point. Really confused me but easily done until I get my head round it lol

so, do you think I need to get an additional switch and relay then duplicate what the wavy line switch is but permanent 12v instead of d+ or just swap wire on original?

sorry if I am missing the obvious :)
 
Ah, is the two position switch the MB part they quote?

if so what additional wiring did you need to do?
 
If the two position switch is already factory fitted then i would suggest you already have both options and no modifications are required

Do you have the MB handbook, read the section on heating and these two buttons
 
No I don’t have the handbook and the switch with wavy lines up is only on and off so not the two position switch you mean I don’t think.
 
I get errors when trying to open the manual at that link but I am on phone so will try on computer later.

the auxiliary switch in those pages is what turns on the Eberspacher when ignition is on for me.

I think it refers to the centre switch in the other pic and that’s what turns on the heat exchanger blowers near the water tank/calorifier on mine.

will see if I can get the manual later and have a read. I do not have the timer/programmer though.
 

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