Habitation area thermostat

Hi guys,

We are presently away at lovely Castleton in the Peak District and the habitation heating is certainly getting some use.

On the A/S Cotswold we have the Webasco diesel/electric blown air heater which generally works well.   However, we are finding that the time lag when the heater trips off and back on again seems to be excessive.

I guess that there is a room temperature sensing thermostat somewhere in the ‘van but where is it ?

When the heating comes on it feels great, nice warm blown air, but it will trip off and we feel positively chilly before it trips back on again.

Is there anything that I can do to lessen the heater off downtime ?

It depends on what controller you have. A/S change the spec on their vans so often that I doubt anyone will know other than you.

As I understand it, the simplest control system does not have a remote thermostat at all. The thermostat is built into the heater itself, in the return inlet. The temperature controller itself is just a simple variable resistor.

You can however buy an external thermostat which plugs into the heater. Like all other things Webasto (and Eberspacher for that matter) it is ridiculously expensive for what you get.

If you have a more advanced controller, it may have a thermostat built-in, but I doubt it. A/S don't tend to install expensive options like that.

I did think about adding an external sensor to mine, but I don't use mine a huge amount in very cold weather and couldn't justify the £60-70 (the cost of the part alone, without fitting).

The Truma combis have a thermostat sensor away from the heater. It looks like a half sphere in black about the size of a 10p coin. Maybe something similar on Webasto.

Thank you for your reply Roopert.   I guessed that this would not be straightforward.

Perhaps I need to do a bit more research or discuss it with my dealer, but generally all I get from them on things like this is a lot of head scratching and blank looks.

Overall the system is working but when the heating trips off the van cools considerably before it cuts back in again.

Yes, mine is exactly the same. I tend to end up with the control set a bit higher than I want, so that the lowest temp is comfortable - which means that the highest temp is bit too warm!

Not sure whether you have a AirTop 2000 or another model. This is an example:

https://www.butlertechnik.com/webasto-heater-parts-c111/webasto-air-top-2000s-temperature-sensor-9005076a-p146

IIRC you just need to plug it in and move a wire link, so not exactly complicated to do.

Thanks Roopert, this may well be what I need.   My Webasto is a Dual Top RHA 102 and I have just checked the link that you provided and I have located the correct part for my Webasto.

I would have thought that the motorhome should have one of these fitted already, the type of thing that Paulmold described above that he has with his Truma unit, but I am positive that there is nothing obviously visible in the Cotswolds interior.

Check up high, the Truma ones are almost at ceiling height (hot air rises).

The room thermostat for my Truma system on the Nuevo is as descibed by Paul, and is located above the Hartal door opening.

Cymro

It's probably best to go back to the Webasto itself and see if there is anything plugged into the remote thermostat connector - that way you can be certain that there's not one hidden away somewhere!

Edit: actually might not be that easy, as it looks like the plug/socket is on the wiring harness, and it's not clear which end of the harness it is...

Edit 2: If the procedure is similar to adding an external thermostat to an Air Top 2000ST, you need to cut off a resistor and crimp in place a socket (on the harness) and then the external thermostat should just plug in. I should add that crimping this type of terminal is not always trivially easy (but is not exactly complicated either).

Cymro wrote:The room thermostat for my Truma system on the Nuevo is as descibed by Paul, and is located above the Hartal door opening.

Cymro

I am a retired gas heating bloke. (I'm not an 'engineer' -they make engines and have skills which modern so-called engineers will never hope to achieve). I had a Truma which went faulty and I traced it to the thermostat in the black blob above the door. I pinged off the black plastic and in there was a component I recognised from domestic heating boilers. I went into my garage, got one out, fitted it and the system worked properly again. The thing costs about £3.50 from your local plumbers merchant. If you take the old one and show them, they may well be able to sell you a replacement. For a couple of drinking vouchers, you may consider it worth a try.

Thank you for your input gassygassy, but I just wish that my solution is as simple as you describe.
Sadly, I do not have any such ‘black blobs’ mounted anywhere in the Cotswold.
I think that Rooperts suggestion of an in-line thermostat in the return pipework seems to be the most likely, but his solution would be beyond my capabilities. 
Shortly after I bought the Cotswold it needed to be returned to the dealer for a number of faults, one of which was the Webasto heater. I now wonder whether it was reassembled correctly or more importantly reconnected correctly.   
It seems that a return to the dealer is urgently required...... argh.

Seastones wrote:an in-line thermostat in the return pipework

It doesn't require any work to the pipework! It should involve just 2 electrical connections and the need to site a thermostat somewhere suitable.

To be honest, any Webasto authorised installer should find the work almost trivial. The issue for me would be one of cost, and the knowledge that, as gassygassy says, the part from any other source would cost £3.50 rather than more than ten times that amount from Webasto!

I should add, though, that even an external thermostat may not completely solve the issue. Like any other heating system, Webasto engineer into their heaters an element of hysteresis - the purpose of which is to make sure that it doesn't come on and go off too frequently, as this can lead to excessive wear on some components and can also annoy the owner. It may simply be that, by design, the control system has a very wide gap between the on>off and off>on temps.

What Roopert says is quite true. If you consider your humble domestic fan heater, you set it at a certain temperature, it reaches that temp, switches itself off and you may get chilly before it turns on again. Inside your camper heater there is probably a thermostat, or rather a 'NTC' as they call it (Negative Temperature Coeficient) resistor which changes its value with temperature. Thus the heater knows when it has reached temperature. They do sometimes go wrong, in which case you would need one. There is one on the 'flow' pipe in a water based system like Alde. You do have two in the boiler at home. Again, they are not desperately expensive, something like £10.

Thanks for your replies guy and sharing your knowledge.

I fully understand what you are saying and the reasons for the heater operating in this manner.

At the time of the initial posting of this topic I was in the beautiful Peak District and night time temperatures were dropping as low 2’C, day time highs of 6-7’C, at these outside temps the van cooled quickly when the heating had its ‘off’ periods.    Currently in rainy Leicester with an outdoor temp presently 11’C and the ‘off’ periods don’t seem to be so chilly.

So perhaps the outside conditions had more to do with it than I had initially thought, and also making matters worse the cold draughts around the closed roof vents and from behind the fridge and microwave probably added to the problem.

Seastones, the temperature sensor for the Webasto controller you have on the Cotswold, is located  above the drivers side settee and is fixed to the underside of the overhead cupboards. It is a small black dome like thing located near the tv cabinet, (at least it is on the end bathroom model).

We have a Cotswold EB with the same heating which works fine.

Tony