Webasto Air Top 40 Evo

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Benji

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I'm Benji from Belgium, and i have a camper.
May I enlist your help, there is little good information to be found on the internet.
It always gets too hot in our camper. At first we had the dial rheostat, but I replaced it with a multicontrol for finer adjustment.
An external thermostat with connection to the W bus is used. The thermostat is at a correct place, placed by the manufactory, so that can't be the issue. if I measure these ohms, at the plug I get 16.7k, it was 17.5 degrees in the camper, this seems a lot to me!
When i blow on the thermostat i see the resistance reading drops to a 14.4k so it seems it is working.
Anyone have an idea

Thank you in advance for your time.

Benji
 
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Not quite sure if it's the same issue, but we have the Airtop2000 & the temperature sensor is in the cold air inlet in the drivers step. Consequently, the air being "sensed" is much colder than the actual temperature in the cab. If we set the temperature on the controller to 17-18C, the heater never shuts down & the cabin is much too warm. Setting the temperature to around 11-12C is about right. Try starting the heater, let the cab get to a comfortable temperature & slowly turn down the thermostat until the heater goes into standby mode.
 
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Your question is a bit confusing - you say that you have an Evo40 but they do not use an external thermostat let alone one connected to the W-bus. None of the modern heaters use a thermostat.
Are you talking about an external temperature sensor? Even that is not making sense as the resistance of the sensor should be 10 -12 KΩ
 
What is the actual problem?

The Multicontrol is not a thermostat, the temperature that is set on it is sensed either by the ecu's temperature sensor or by the external temperature sensor but you must site the sensor in such a position that it is sensing the temperature at the height where you are saying that it is too hot.
Basically ignore any mention of temperature and just use those numbers like the rheostat and set it at your own comfortable level. You can get perfectly satisfactory temperatures with the rheostat by using it to set the temperature at your comfort level the same.

As said the external temperature sensor is not connected to the W-bus - if yours is there is something wrong with the installation.

I don't know what is happening with your sensor resistances though as they appear to be too high unless you are in freezing temperatures.
 
You posted this message as well:

Webasto Air Top 40 Evo​

In our case the position of the thermostat is perfect, that's what makes it so strange. thank you for the feedback

Benji

What is this thermostat that you keep referring to?
 
I meant the location of the temperature sensor, Google translation error i think.
I set the desired temperature on the multicontrol, just like I used to set the rheostat to a certain position. For example, if I ask for 20 degrees, it will easily be 23 degrees, measured with a separate thermometer at the place where the Webasto temperature sensor is located.
the temperature sensor is plugged into the same cable bundle where the rheostat used to be and now the multicontrol is plugged in.
I will try to remove the temperature sensor tomorrow and check the connection of the cable, maybe a bad contact explains the high value
If I understand correctly, the operation of the Webasto is as follows, when the requested temperature is reached, the Webasto continues to heat at a lower level to maintain the temperature, isn't it correct? does it never go out?

Again, thank you for your help,

Benji
 
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The external temperature sensor should be connected to this position, x5, at the ecu ( there isn't normally cabling present for it in a Evo55/40 loom, so I don't know what you have yours connected to):


x5.JPG
 
I managed to check the cable connection on the webasto, and as you indicated it is on X5, so that's OK. The motorhome manufacturer wrapped the w-bus and the temperature sensor together, which is why I thought it was one cable. However, when I just did a measurement in the camper on the connector of the temperature sensor, he indicated 19.44K on the ohm meter at 14.4 degrees.
Started the heating today and set it to 18 degrees via the multicontrol, normal heating position, started at 14.4 degrees and after 40 minutes it had already reached 22.7 degrees, the fan was still running at the same speed, this is not the intention, what do or is wrong? I have almost no experience with Webasto.

Thx for all the help, Benji
 
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Are you measuring the resistance of the sensor whilst it is still connected?

What height do you have inside your van?
Then what height is the sensor placed at?
 
I measure the sensor disconnected. the height of the mobile home inside is about 2.1m and the sensor is at a height of 1.3m, placed 10cm from a corner by the manufacturer.
I am an electrical engineer by profession :)

thx, Benji
 
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The sensor is far too low, try at 1.6 - 1.7m. It can go even higher if needed.

Your resistances do seem to be out though - 15.3 degrees on the sensor that I have just tested and the resistance is 16.01 KΩ
I will test several later to see if there are any that match yours closer.
 
Move the temperature sensor is unfortunately difficult to do.
Can you explain me how the Webasto should behave when the requested temperature is reached?
Can I safely use the heating on eco mode most of the time, or is this not good?

Thx, Benji

20230325_165254 (Large).JPG
 
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The heat output will drop as the temperature is reached. You do need to put the sensor higher up otherwise you will never get close to how you want it to behave.
When I sell a heater with a remote sensor I tell the buyer to not fix the sensor in position until they have found the correct height to achieve their own comfort level matching the temperature. Every van and person is different as to what they require so you must move the sensor into a position that gives the required effect.
Running on Eco mode all the time is not good for the burner, it is better to run a smaller heater on full heat all the time rather than a larger heater on low all the time. You will suffer from premature coking of the burner mat if a heater is run on low heat all the time.
 
16.7 KΩ @ 14.3 degrees on one sensor.
17.5 KΩ @ 14.1 degrees on another one. 17.9 KΩ @ 13.9 degrees. 13,5 KΩ @19.5 degrees.
 
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@oldiebut goodie, thx for everything, you're so kind!!!
it is a factory camper. I will continue to test whether I can find an agreement somewhere with the temperature set and effective, for example setting 3 degrees less gives the desired effect. If this does not work, I will still move the sensor.
For example, if I let the webasto run at night on eco and then on normal for a few hours, would this still keep the burner clean, what do you recommend?

Thx Benji
 
Benji said:
@oldiebut goodie, thx for everything, you're so kind!!!
it is a factory camper. I will continue to test whether I can find an agreement somewhere with the temperature set and effective, for example setting 3 degrees less gives the desired effect. If this does not work, I will still move the sensor.
For example, if I let the webasto run at night on eco and then on normal for a few hours, would this still keep the burner clean, what do you recommend?

Thx Benji
Click to expand...
As has already been said. Ignore the temperature setting on the controller, it’s only indicative. Just set the temperature where it’s comfortable. Ours is around “12” and the temperature in the van is warm enough to sit in shorts & t shirt when the external temperature is below zero.
 
Ideally the heater will be sized according to the projected usage and the size of the van. I get the impression that your van has a heater that is too powerful for what you need.
A 4Kw heater in a small van will never get used correctly and will always be run at too low a heat output for too long unlike a 2Kw one.

It seems as though you are thinking about 8 hours at low then normal or boost for a couple of hours - you will still be running the heater for the majority of the time at low heat with the consequent risk of premature coking. A couple of hours at high heat will help burn off deposits but this regimen is not optimum.

I fitted an Evo40 to my own high top LWB van BUT I never run mine at low heat and do not have it on for overnight heating. Mine is purely for a large amount of heat quickly after being out walking with my dogs.
 
My semi-integrated camper is 7 meters, hence the 4 kW version. We have a cat that never goes outside and always lives in a temperature of at least 17 degrees, so that's why warming up at night is necessary. If we use the heating 20 days a year it will be a lot, we are more away on the warmer days, but I take your advice to heart and will use it as little as possible on low and if this has happened, let it burn on normal for a few hours afterwards. Thx, I learned a lot about Webasto here.

I wish I could return the favor, buy you guys a beer when I'm around :)

Benji
 
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