Webasto Thermo Top with CAN-Bus?

Hello everyone!

I recently won an auction for a Webasto Thermo Top Z/C...
Everything is connected according to the diagram, but nothing is happening.
This component was installed as an OEM product by Mercedes.
Does anyone know if the heating system doesn't normally use pin 1 (+12V switching signal) as standard?
, but is controlled via CAN-Bus? The wiring diagram (connection diagram) of Webasto says
Certainly not about that, no wonder, it's also for the retrofit equipment.

The fact is: The heating system's control electronics contain a TJA1054 bus driver and a CAN-filter, so the heating system is likely to be CAN-enabled, but the bus driver may also be able to operate with a single wire!?

One of the CAN-control pins goes to the diagnostic line (pin 2 on the connector), while the other goes to pin 3, which, according to the Thermotop C installation instructions, is an outdoor temperature sensor.

I have already tried to establish a connection with the Webasto Thermo Test window program for the purpose of diagnosis and control of the heating system, but unfortunately without success.
First, with a cheap OBD interface (K-line to diagnostic cable), then with an RS-232 level converter and a differential (RS-485) driver for the two CAN lines of the heating system, and finally with a real CAN dongle... This cost me the whole weekend...

Conclusion: The heating system can be switched on via the diagnostic line in single-wire mode (the DC converter supplies power to the electronics, nothing else), and it also sends some data along the line, but the diagnostic software cannot interpret this data.

Does anyone know which interface actually works for diagnosis, or can the heater only communicate via CAN?

..There's also the W-Bus, I have no idea what that is.


Hope you have some tips for me!

Thank you very much,
Greetings,
Paul

[Translating...]

Hui, da scheinst du aber einen Glückgriff gelandet zu haben

Leider habe ich auch keine richtig befriedigende Idee. Aber wie wäre es herauszufinden, in welchem Benz die sitzen sollte und bei Mercedes mal nach Stromlaufplänen für selbigen zu fragen? Damit müsstest du zumindest die Originalverdrahtung simulieren können. Evtl gibt es eine passende Mercedes-CAN-Schaltuhr...

Alternativ einen Hilferuf an Webasto senden, die sind nach meinen Erfahrungen auch immer hilfsbereit und kompetent. Ob sie allerdings bei deinem Problem helfen können bzw dürfen? K.A.

Gruß
Guste

[Translating...]hallo rammelsberg

zum ansteuern der webasto termotop c brauchst du eine steuerteil von webasto welches den w-bus unterstützt. also eine vorwahluhr 1533 oder ein termocall 90T. ich habe es auch so nachrüsten lassen beim boschdienst und der monteur meinte auch das auf den pin1 der termotop 12v kommen und schon get es. das war falsch. sie geht ebend nur mit dem w-bus zu steuern. die vorwahluhr 1533 hat einen w-bus ausgang und ein statischen 12v ausgang.

gruß frank

Hey, that's good news!

I recently won a 1533 pre-owned watch in an auction, and it should arrive soon...
I'm already looking forward to not having to anymore.
Very Happy

Well, until then, there's still a long way to go. This time, I want to make everything compliant with the German road traffic regulations (STVZO). I contacted DEKRA and they said that if the heating system has an "e-Nummer" (German conformity marking), I can simply install it and don't have to have it inspected. Webasto wrote to me, but I needed an ECE type approval, which the installation workshop had to fill out and stamp.
I think I don't need to ask if I can fill it out and stamp it myself.
Wink.

..no, I don't have my own car repair shop and I also don't work in one...
So, should I still go to the MOT inspection then?

Well, let's see, first of all, the heating system needs to actually function, then I'll proceed from there.

If I make further progress, I will get back to you!

Best regards and happy holidays,

Paul

Hello, fellow enthusiasts!

Frank was right, the heating is controlled via W-Bus. With the new timer 1533, it worked immediately. On pin 1 of the heating device, where the 12V switching pulse is otherwise present, the W-Bus connection of the timer must be connected, and it works. I installed the heating in my Passat 35i, despite the air conditioning and ABS, there was no space problem. Sucking fuel from the return line also works.
Unfortunately, the heating device has a small problem: Sometimes, after a few seconds of operation, it switches to an error state, the light bulb goes out, and the fan runs at full speed. The display then shows F --. Sometimes, the heating system will actually heat up for 20 minutes before it cuts off the fuel supply and malfunctions.
My first guess would be that the fire extinguisher is faulty (as it's also the flame protector).

How do you see it?

Greetings,
Paul

[Translating...]

Die Thermo-top ist normalerweise Diagnosefähig über K-Line, das solltest Du probieren (lassen). Hoffentlich geht das bei Deinem Spezialmodell auch noch so. Es wäre ja auch möglich, daß die Heizung wegen Überhitzung z.B. wegen unvollständiger Entlüftung abschaltet.

Hi!

"Diagnosis" is a good keyword. Has anyone had experience with the Webasto software and the KKL interface from dieselschrauber.de?
I don't think it's a ventilation issue. The heating system sometimes also switches to a fault mode during the starting process (when the fan starts running slowly and the fuel pump starts to sputter...).
Should I not also receive an error message regarding the W-Bus (clock)?
I'll try to replace the burner (with the glow plug) under suspicion. I still have an (slightly older) Thermo Top lying around...
Maybe it will also help me if I measure the voltage across the light bulb when it starts with an oscilloscope, I'll try it out over a few days.

If I learn something new, I'll get back to you!

Greetings,
Paul

[Translating...]Hallo,

ich würde auf die Brennstoffversorgung tippen.

Ich habe mir vor kurzem auch eine Thermo Top C in meinen Audi80 B4 TDI eingebaut.
Ich hatte zuerst die Brennstoffversorgung an die Vorlaufleitung angeschlossen, und auch immer das Problem, dass die Heizung immer nur sporadisch ging.
Nachdem ich dann dir originale Brennstoffleitung der STH mit nur 2mm Innendurchmesser bis nach hinten zu den Tankanschlüssen verlegt hatte, hatte ich keinerlei Probleme mehr.

Liegt wahrscheinlich daran, dass die Pumpe zu schwach für die dicken fahrzeugeigenen Leitungen ist.

PS: Bei mir ging das verlegen relativ einfach, da an den Gummiaufnahmen für die Kraftstoffleitungen in der Mitte noch ein Loch frei war, das genaupasst.

mfg
sLindi

Hello everyone!

Here's a quick status update:

The fuel supply isn't the issue; the problem is with the control unit. Once the engine or the coolant reaches a certain temperature, the control unit shuts down with an error. I initially suspected that the issue was with the disconnected relay for the interior fan, but I finally installed that relay. Now, the heater doesn't turn on at all and immediately goes into error mode. The relay is briefly pulling in. I suspect that the CAN bus is now affecting me again. It could be that a message is being sent over the bus to the comfort control unit for the interior ventilation (which I don't have...). Since the message is not received and acknowledged, an error is generated.

With another control unit that doesn't use CAN, the heating system works perfectly, of course.
Well, I think I'll focus again on the diagnosis, or try to simulate a CAN-Bus.

Best regards,
Paul