Webasto Z/C-D won't start

Hello everyone,

I recently purchased a used Thermo Top Z/C-D.
Before I put them in the car, I wanted to test them to see if they were suitable.


Structure:
'Water cooling still active, TT connected to the battery, resistor used as a replacement for the dosing pump, diagnostics possible via PC.'

Here's what happened. First, there were always errors with the dosing pumps. After I added a resistor (without the dosing pump installed yet), this error no longer occurs.

With the PC, I was able to turn on the water pump, the combustion air blower, and the glow plug.
However, there's something strange about it. When I turn on the heating element, the water temperature reaches 23,000°C or even higher. Either something is wrong, or who knows what...

I read in this forum that pin 3 of connector X1 needs to be connected to 12V to activate the auxiliary heater function. However, nothing happens. But when I connect pin 3 to ground, the diagnostic software shows 'Supplemental Heater Request.' 'But nothing happens anyway. The 'Device state' always shows 'OFF State'.'

When pin 1 is connected to 12V, the software displays 'Main switch on.' After approximately 10 seconds, the error message 'Communication error on internal bus' appears.

What am I doing wrong that it won't start?

Does it only run with one clock?

Best regards,
Ralf

I'm not sure if this also applies to the Z/C models, but with the successor auxiliary heating systems from Webasto, there were vehicle manufacturer-specific versions that used either +12V, or CAN, or W-bus to activate them.

If you encounter a version like this, it will not function properly without a vehicle-specific counterpart (e.g., a clock, or an AI system, or...).

Therefore: Does it mention anything specific to a particular vehicle manufacturer? Possibly an OEM part number?

Regards,
Guste.

Hi,

On one page, it says:

BMW 64.12-8 387 111
Thermo Top z/C
Webasto 64252A

I only know CAN as a differential transmission. And with the Z/C interface, the lines are fixedly assigned. That would only leave pin 1. Pin 2 is for diagnostics, and the rest of the pins are also in use.

Is there a TT C or Z/C model with a 6-pin connector that supports CAN bus? (because it would only require one pin).
It's strange that you can only select the W-bus in the Webasto test software. If I then place my adapter on pin 1, I can't access it using the software.
It only works when Pin 2 (diagnosis) and 'Thermo Top BMW' are selected. However, I can only run the component test. Unfortunately, I can't turn it on. It seems to be a bus specific to BMW.

Best regards,
Ralf

Ralf82k wrote:

It seems to be a bus specific to BMW.

Unfortunately, I don't have any precise information about the BMW STH, but I strongly suspect that's the case.

With a bit of luck, there's only one Webasto clock specifically designed for BMWs that you could retrofit. Unfortunately, in some BMW models, this feature is controlled via the dashboard, steering wheel, or navigation system, similar to how it works in current Volkswagen Passat and Phaeton models.

Regards,
Guste.

I've read something similar before, that when the engine temperature reaches a certain level, the car's ventilation system automatically adjusts accordingly. If it's not connected to the bus, the SHZ will malfunction.
It's strange that the commissioning of the combined heat and power plant was supposedly in 1997. Did BMW already have electronic ventilation flap control systems back then?

I'll probably have to get a different one, one with 12V or at least with the W-bus.
Are auxiliary heaters always able to start with 12V? Are there any options with a bus as well?

Best regards,
Ralf

Take a look at this page; you might find the information you're looking for there.
http://www.handy-fernsteuerung.de/

Ralf82k wrote:

I've also read something similar before, that when the engine's coolant temperature reaches a certain level, the vehicle's ventilation system is adjusted accordingly. If it's not connected to the bus, the SHZ will malfunction. It's strange that the commissioning of the combined heat and power plant was supposedly in 1997. Did BMW already have electronic ventilation flap control systems back then? I'll probably have to get a different one, one with 12V or at least with the W-bus. Are auxiliary heaters always able to start with 12V? Are there any options with a bus as well? Best regards, Ralf

BMW even had electronic ventilation control systems as early as the late 1980s; they were always significantly faster than VW and other brands within the group;).

I installed a STH (likely referring to a heating system) from a 2000 BMW 520d into my Polo. It's combined with a universal wiring harness from Webasto, and everything is new except for the muffler, which was still in good condition. If you want to install it universally, you'll need the universal wiring harness. However, this eliminates the need for any vehicle-specific components, and the clock will be installed. If the clock isn't a problem, this is the most practical approach, as it also allows for the simultaneous connection of various heating devices.

EDIT:

Just a side note: The STH (presumably a specific device) can also be diagnosed using a Webasto tester. Perhaps the problem lies in the control unit of the STH.

Hello, I've managed to get the Webasto test software working. All the elements of the SHZ (heating system) seem to be functioning correctly. The only thing that might be defective is pin 1 of the control unit. However, even when I apply 12V to that pin, the software shows 'main switch on.' A little later, something happened with the bus, and there was an error.
I don't suspect a faulty control unit.
I haven't tried that with a watch yet. What watch do you have? Is it the 1530 or the 1533?

Best regards,
Ralf

Hello,

I have the watch, model 1533.

Do you perhaps have any more data from the donor vehicle? FIN would be nice.

FIN?? What is that?
So, your SHZ is then running over the W-Bus. Are there any issues when the SHZ (heating circuit valve) attempts to control the ventilation via the W-bus at water temperatures above 30°C?

Best regards,
Ralf

Hello,

FIN= Vehicle Identification Number;)

My starter generator is running with the Webasto 1533 timer and the universal wiring harness, and that's all.

As I mentioned, it was from a BMW 5-series, manufactured in 2000. There's nothing wrong with my bus, at least not with mine, and it runs perfectly fine, no matter the temperature.

Aso . Unfortunately, I don't have it.
I'll probably start by getting a 1533 movement. Then I can see what else is possible. If it stops working at a certain temperature, then I'm just out of luck and have to find another one.

Best regards,
Ralf

A colleague of mine had a similar problem with his 1997 525tds (likely a model similar to yours) – it would start, but then stall. We sent the entire heating unit in for a complete overhaul because the control unit was defective, as water had leaked in (apparently, someone before had not properly tightened the cover )

After that, it worked perfectly again.

My car used to have problems too, but it displayed a "flameout" error.

The gasket between the heater and the exhaust was missing, and I also replaced the glow plug because it had been changed from a metal to a ceramic type/improved version.

If you can somehow figure out the last 7 digits of the FIN, it would be easier for me;).

No, I won't be getting those anymore. I'll get the watch, and then we'll see what happens next...