# Cab heating problem



## ojibway (May 9, 2005)

Hi all,
I have a similar problem to that posted recently by johnnyp2269 though I think the solution may be different.
Mine's a Mercedes 316cdi.
The cab heating works but only when on the maximum temperature setting. Turn it down a fraction and it goes off. I'm worried it's going to fail altogether soon.
I was going to book the van in to have it looked at but seeing the quick response and positive result here I thought best give it a go!
Mike


----------



## rayc (Jun 3, 2008)

ojibway said:


> Hi all,
> I have a similar problem to that posted recently by johnnyp2269 though I think the solution may be different.
> Mine's a Mercedes 316cdi.
> The cab heating works but only when on the maximum temperature setting. Turn it down a fraction and it goes off. I'm worried it's going to fail altogether soon.
> ...


Mike, the cab heating is directly proportional to the engine coolant temperature. Is the engine getting up to operating temperature? Are the hoses in the engine compartment as warm as would be expected i.e. very hot to touch? When the heater valve is at maximum how hot is the flow hose to the heater and how warm is the return hose? Perhaps there is an air lock in the heater matrix. On my Fiat there is a bleed valve built into the heater return hose in the engine compartment which alllows the heater to be bled. Ray


----------



## JeanLuc (Jan 13, 2007)

Don't forget that the Sprinter cab heating system is controlled by a thermostat. So, if the van has reached the set temperature and you then turn down the heat control (even a little bit) the system will stop putting out warm air until the van's temperature has fallen to the new setting.

The more telling test might be to set the control at a mid-point and leave it there for half an hour until the temperature stabilises, then increase it by a little. You should soon be rewarded by a satisfyingly warm flow of air from the vents (not the ones on the top of the dash above the radio though, they are for fresh air only). n.b. It takes a couple of minutes for the temperature sensor to activate any change in the heat output.

It might be worth checking that the temperature sensor has not become blocked with fluff, dust or other debris as this can affect the operation. The sensor is a small rectangular opening on the central dash area, in the form of a plastic grill.

Philip


----------



## ojibway (May 9, 2005)

Thanks Ray, thanks Philip, I will check these things out.

I have had the engine at normal running temperature, according to the temperature gauge anyway - we were driving back from Spain, over 4 days the weekend before last when I noticed the problem.
It was a case of all or nothing.

I also noticed the the outside temp gauge on the instrument panel was showing the engine compartment temperature, about 45c where as before it had always shown the outside temperature, in the 16c to 24c range. I don't know if that has any bearing on it.

Anyway, I'll check things out tomorrow.

Mike


----------



## trek (May 1, 2005)

Hi

is this a new problem was the heat output ok previously ?

& I agree that the outside temp gauge readings seem a little odd 


If you have always found the heater to be on the cool side I was wondering if your Sprinter has the Eberspacher Heater Booster fitted that you may not know about 

on the pre 2006 Sprinters:-

To see if your Mercedes has one, look for a centre switch on the heater controls marked with a heater icon (series of waves).

also take a look under / behind the front nearside headlight - do you see an aluminum device with some rubber pipework running from it & a metal pipe going to a very small exhaust box. 



if you have this it is a booster to add extra heat to the engine coolant to warm up the cab, it works when the engine is running & the heater temp control set to hot ( it wont work if there's not much diesel left in your fuel tank) just press the wavey lines switch - sounds like a jet engine when it starts up


----------



## ojibway (May 9, 2005)

Thanks Trek, I will check this out too.

It is a new problem, not that I have used the heater that often, travelling more in warm weather, but I'm sure I have been able to control the heat output previously as one can with any car or van.

The temp gauge problem is new, though for a while it reverted to outside temp after starting up the van but then back to engine compartment temperatyre.
I had this with my previous van, a 2002 Sprinter based Aclass Rapido. I just assumed that Rapido had not bothered to place the sensor in the right place! It never did show outside temp!

My own thoughts on the heater is that it could be the valve that opens/closes when when the control knob is turned. Could the link just have become loose? I'm not sure where to look.

Anyway, it's nice and sunny today so I'll have a look around.

Thanks again everyone!
Mike


----------



## teemyob (Nov 22, 2005)

*Heating*

Is the Heating TempMatic and do you have Factory A/C and the Eberspacher Add/Boos Heater as mentioned by trek?

TM


----------



## ojibway (May 9, 2005)

Hi teemyob,

I'm not sure about the heating being tempmatic but the A/C is factory fitted and it has the Eberspacher boost (I hadn't realised this until today!)

I've had a look today and not have not had much luck improving the system.
As I said before - I get plenty of heat at maximum setting but as soon as I turn the knob to reduce the temperature it sort of goes to lukewarm. No nice gradual reduction or control.

I should add that I had the van idling on the drive to bring the temp up and the engine temp only went to 60c. When I turned on the boost it went up a bit more just touching 70c. Normal driving temp is pretty much a constant 80c.
I shall take it out on the road tomorrow.
Mike


----------



## teemyob (Nov 22, 2005)

*A/C Tempmatic*

Sounds like it may be the sensor. Make sure the tiny square vent is clear and check the engine temp at the pipes under bonnet.

see This topic of mine here.

Let us know how you go on?

TM


----------



## trek (May 1, 2005)

now that you've discovered that you have the Eberspacher booster heater fitted don't forget to use it on these cold days it helps the engine warm up quicker ( & the cab hopefully)


just check that it is actually running by switching it on when idling and listen for the roar as it strarts up & the initial smell of the diesel

they apparently can be troublesome if they are not used enough (bit like air con)


----------



## teemyob (Nov 22, 2005)

*Eberspacher*

Fired ours up today (the eberspacher) as it has been stood unused for a while. Started first time.

TM


----------



## ojibway (May 9, 2005)

Hi teemyob and trek,
Like you say, I didn't even know I had the booster!

As I was trying things out yesterday, engine idling on driveway, I did turn the booster on but there did not seem to be any noticeable change in temp. I also listened out for any noise as with the interior Eberspacher heater - bit like a jet engine - but heard nothing. I assumed however that it might just be a smaller unit therefore quieter.

Anyway, the sensor seems to be clear visually. But, I'm surprised there should be a temp sensor for the cab heating when the controls are all mechanical (I think).

I'll take it out for a drive today and see how the engine temp behaves. It should go up to 80c.

If the booster does not work who should I take it to - MB commercial garage or independent garage or Eberspacher specialist? I have the van MOT'd and serviced by a reputable, small country garage who also service all the community MB buses.
Mike


----------



## JeanLuc (Jan 13, 2007)

I have assumed in my earlier reply, that you have a previous generation Sprinter 316 (i.e. the one with a 2.7 litre, 5-pot engine). If not, the following may still be relevant in principle.

The picture below shows the cab heater control unit and I have marked some relevant bits.

The sensor is part of the dash unit and the heat setting dial is not mechanical as you had presumed, but is linked electronically to the temp sensor and a thermostat in the heat-exchanger system. Hence, when you turn down the temp setting, the valve shuts off hot water from the heat exchanger and the air goes cool until the lower cab temp setting is reached.

Regarding the auxiliary diesel heater (which I thought was Waeco, but am prepared to accept that Teemyob knows best that it is an Eberspacher) I believe that is controlled by a temperature sensor too. So, if you switch it on when the engine is already warm, it may not fire. I think you need to test it first thing on a cold morning.

Hope this is useful.

Philip


----------



## teemyob (Nov 22, 2005)

*Heater*

Hello,

If the Eberspacher is not firing up, you would be better off taking it to a Specialist. Mercedes Delaers may not even know it is there, may as well be asking some of them for round triangles. One dealer did not even know how to start my SprintShift!.

If you look inside the wheel arch of the nearside front cab. Look towards the front of the wheel for a tiny exhaust silencer coming from the eberspacher (located behind the front nearside headlamp). This should blow and heat up when heater boost is on.

With regard to the heater controls Yes both the Manual and Tempmatic look Analogue (both sets of controls look almost identical) but if tempmatic the vents are motor controlled behind the facia.

TM


----------



## teemyob (Nov 22, 2005)

*Info .pdf*

Here is some more info for you to download


----------



## ojibway (May 9, 2005)

Well, after all your help I thought it only polite to keep you up-to-date!

Yesterday I took the van for a spin.

- I tried the booster after starting the engine but gave up when it did not appear to fire up.
- Engine temp came up smoothly - to 80c
- The heater output worked OK at max but reduced to lukewarm when control knob turned fractionally
- The outside temp gauge showed 40c to 45c even before the engine was up to operating temp, then later I noticed it went down to 21.5c then just as suddenly went back up to 45c!
- When I got back home I checked the upper water pipes and all seemed nice and hot

Yes, I take your point teemyob, go to a specialist for the Eberspaucher.

So, there I am. I guess I'll be making an appointment with the garage.
Thanks for the help and the download Eberthingy instructions.
mike


----------



## teemyob (Nov 22, 2005)

*Problem*



ojibway said:


> Well, after all your help I thought it only polite to keep you up-to-date!
> 
> Yesterday I took the van for a spin.
> 
> ...


Tempmatic I am thinking, Possibly part of the problem.

One of the sensors that may be faulty (thermistor) is located near the front number plate

TM


----------



## ojibway (May 9, 2005)

Hi teemyob,
I'll look for the sensor.
Are you saying it could be part of the heating problem or the outside temp reading?
Mike


----------



## teemyob (Nov 22, 2005)

*Temp*



ojibway said:


> Hi teemyob,
> I'll look for the sensor.
> Are you saying it could be part of the heating problem or the outside temp reading?
> Mike


Yes, it could well have something to do with it.


----------



## dikyenfo (Feb 16, 2008)

Makes interesting reading but could the problem be just the cable connected to the control knob. Hence the slight movement making a big difference to the water flow going through the heater matrix.


----------



## teemyob (Nov 22, 2005)

*Water Flow*



dikyenfo said:


> Makes interesting reading but could the problem be just the cable connected to the control knob. Hence the slight movement making a big difference to the water flow going through the heater matrix.


As far as I know there is no flow control on the water. The baffle from the heater matrix is controlled by a thermistor or a series of thermistors where tempmatic is fitted.

TM


----------



## ojibway (May 9, 2005)

Yes, dikyenfo, that is what I thought it might be but teemyob points out it is more complicated than that.

I have just located the sensor for the outside temperature.
Looks clean and does not look like it could be affected by the engine compartment temp - it just occurred to me that it is maybe flipping between Fahrenheit and Centigrade! I can't think in Fahrenheit so have everything in Cs! But, just checked conversion. 22c is more like 72f whereas the gauge was alternating between 22c and 45c!
regards, Mike


----------

