The Webasto water pump can be tested through the VCDS program for VW cars.
The idea is to activate the pump when the car engine isn’t started, this way it will be possible to listen to the front right side of the bumper to determine if the pump is running.
The following steps will guide you through the steps to start the pump:
- Connect the VCDS cable and turn the ignition key to power up the instrument panel
- Open VCDS and click the “select control module” button
- Then select “Aux. Heat”
- Then select “Output tests”
- The next dialog is a step-vice guide to activate different components associated with the aux heater
- Press next and activate and go to the front of the car and listen:
- If no new summing sound appears the pump is broken. Look at this post on how to replace the pump.
- If a summing sound starts and stops again when continuing the guide the pump is most likely working correct.