Webasto Heater Circulation Pump: Installation Guide

Hello everyone,
Today I wanted to replace the circulation pump of my Webasto auxiliary heater in my Golf. The old pump came out with a lot of effort, but I can't seem to properly secure the new pump! This part is simply attached to the housing of the heater using a hose clamp, and the impeller shaft of the pump should tighten against the inside of the heater housing, but it's not doing that!
Now the whole thing is leaking, and coolant is flowing out.

I couldn't find any seals or similar parts there either. How did you manage to attach the pump?

Please provide a quick update, as the car is currently unusable for this reason, but I urgently need it back in working order.

Thank you in advance.
Euro.

Hi!

Okay, so if the Webasto T46 is similar to the BBW46 (with the pump positioned parallel to the round heat exchanger housing), then there should be an O-ring on the front of the plastic nozzle on the pump (the one that connects to the heat exchanger). There should be a slight groove on the plastic part for this O-ring.
That should make it airtight.
You should be able to find such a ring at a hardware store...

Greetings,
Paul.

Webasto has a very good hotline that will certainly help you quickly and competently, and it's free of charge (except for the phone charges).

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It can also be used as a verb, meaning "to gust."

The pump is now installed and leak-proof!
The trick is to first place the sealing ring on the nozzle of the circulation pump, then insert the whole assembly into the burner housing and tighten it with the hose clamp.

But:
The auxiliary heater turns on and then shuts off again? What could be the cause?

It is a DBW 46 from Webasto.

I've only had the car for a short time and have absolutely no experience with parking heaters.
Could someone give me a general overview of what should happen and in what order?

When I press the start button on my scooter, it takes about 30 seconds, and then I hear a noise that sounds like a turbine coming from the front left side, near the fender, where the starter motor is located.
At some point, the turbine 'kicks in' and 'spins faster?'. From the back of the tank, you can hear a 'tick-tick-tick' sound (fuel pump?). Then, smoke starts coming from the exhaust at the front of the SH.
The blower inside starts running.
After approximately 90 seconds, the ticking sound from the rear stops, and only the blower motor inside the car continues to run (heating blower motor?).
The indicator light (SH) inside will remain green until then.

Any ideas?

Sure, here's the translation:

'Thank you in advance.'

euro

Hello!

I would check the coolant temperature sensor; it's located on one side of the burner and is screwed in from above.
Normally, the interior fan should only start running after the coolant has been preheated somewhat; in my case, it always started around 15 minutes later...
The temperature sensor might be faulty and reporting an excessively high temperature, which would cause the heating system to shut off.

Greetings,
Paul.

Could that also be the case if the new (used) circulation pump is also defective? Then the entire unit would become too hot (because the coolant isn't circulating), and then the sensor would shut off as well?
Or, did any fuse (a thermal fuse, if such a thing exists?) blow due to the faulty circulation pump that was previously installed? If so, where might it be located, and could I temporarily bypass it for testing purposes?

How can I test something like that (without any electrical knowledge - unfortunately)?

Regards,
euro

Yes, if the water pump isn't working, the heating system would overheat and shut down after a short time. There is also an emergency shutdown that supplies power to the dosing pump. If the heating control unit doesn't shut off, this safety switch cuts off the fuel supply. The switch is located at the top of the heater on the opposite side from the temperature sensor. You can identify this thermostat switch by a transparent rubber cover with a switching element underneath, which has a red reset button. When the switch trips, the red button (more like a pin) pops out. After it cools down, you can push it back in.
But if your dosing pump is making noise when it starts, then this switch probably hasn't been triggered.
Try powering the pump with 12V directly from the battery after you've unplugged the connector at the heater unit.
Does the heater (the outer casing) actually get hot within the first 90 seconds after it's started?
If it shuts off after 90 seconds, it could also be a dirty flame sensor. This is located on the top of the heater and is held in place by a metal clip. It should look like a small white cap with a cable that connects to the main plug.
This sensor detects the incoming light, which indicates that the flame in the burner is lit. It might be dirty due to soot buildup, in which case you would just need to wipe it verschandeln with a tissue.
Otherwise, to proceed with further diagnosis, you would need an ohmmeter to test components such as the temperature sensor or the flame sensor.

Hopefully this helps for now; if you have any more questions, just let me know!

Greetings,
Paul.

I was finally able to test the pump, and it only runs when I connect it directly to the battery with positive and negative terminals.
That's why the heating comes on and then turns off again when everything is hot, but the water can't be circulated.
Does that mean the system won't go into 'error' mode? It's only too warm at the moment, right?

Is there still a logic in the DBW46 that measures whether the circulation pump is actually running?

Are there any specific fuses for the circulation pump?
Are there known cable breakages associated with the DBW46?

Can I simply connect a switch in between that provides the positive and negative connections from the battery when I turn it on, or is there another signal required for the control unit?

Regards,

euro

Hello euro!

In principle, there's nothing stopping you from simply connecting the pump (ideally with an additional relay) to the timer switch.
To my knowledge, the pump is not checked by the control unit (newer devices like the Thermo Top C do this, apparently), so it doesn't detect whether the pump is connected or being controlled externally.

Perhaps the following might be helpful as well:
On the website www.techwebasto.com, you can find installation instructions and wiring diagrams under "general access" -> "automotive". These documents specify which pin on the control unit is used to connect the pump.
You could try connecting a test lamp or similar device there and measuring the voltage against ground. If you get 12V, then the control unit is working correctly, and the problem lies somewhere in the connector or wiring harness.

Keep us updated!

Best regards,
Paul.

The SH is now ).

Ich habe einfach eine neues Kabel zwischen Umwälzpumpe und Masse verlegt, sowie ein neues Kabel zwischen dem Steuergerät (3.Pin vom 8-Poligen Stecker) und dem Pluspol der Umwälzpumpe. (Besonderen Dank an 'rammelsberg' wegen dem Link zur techn. Doku)

'However, what's no longer working is my residual heat utilization system. This is a switch that should turn on the heating fan (and possibly the circulation pump for the solar thermal system?)'
Since I didn't install the SH myself and therefore don't know the wiring for it, here's my question:
How could this waste heat recovery system have been connected in the past that is no longer working now?
(The switch has 3 terminals and is illuminated when it is turned on.)

When I still had the third pin on the control unit connected and directly wired to the circulation pump, the switch at least used to turn on the heater fan. Now, nothing happens anymore.

Sure, here is the translation of the text from German to English:

'Hello.'
euro