If smoke is being produced then the fuel is being ignited by the glow plug and the burner is coming to life.
I can't explain why the tech decided to replace an item on the work order when, if what you suggest is correct, initial diagnosis showed the fan was at fault. I think you've got good cause to complain and have the cost of the unnecessary parts refunded. I would also be discussing a labour-free removal/re-fit if you decide to have the fan unit replaced, as this should have been done in the first place taking account of the fault codes the tech suggests were originally logged.
It's not impossible to wire the fan the wrong way round, but this would mean removing the existing pins from their connector and re-fitting incorrectly. This isn't something that would be required at any time, therefore I'd say you can discount this idea. And, even if the fan were to be wired incorrectly, the chances are it just wouldn't work.
The Fan connector cannot be placed into the controller the wrong way around
If the fan isn't working, then the fumes will exit from the top.
Did the technician provide you with a diagnostic report showing the faults present at the time you first took the car to them?
1. If yes, and it shows only a fan issue, then you can be pretty sure the fan unit has failed, and this should have been repalced.
2. If the original fault showed only a glow pin issue, and now you have a fan issue, then perhaps the tech hasn't re-connected the fan wiring to the controller, in which case they should rectify under warranty without charge.
------------------------Testing the Webasto using VCDS - ------------------
Only run the Webasto self-test on a cold engine
Only run the Webasto self-test for a short period of time without starting the engine.
Reasons for above care are due to the standard Webasto setup on the A2 not using an external pump to circulate the water through the cooling system. The A2 uses the engine-driven water pump to circulate water, therefore it is possible to boil the water in the Webasto and damage the unit.
When running in self-test mode, the Webasto's controller does NOT take notice of the water temperature.
If an external circulation pump has been fitted to allow the Webasto to pre-heat an engine, without the engine needing to be run, ensure the pump is operating.
It's useful to run the self-test without the engine as you can hear the Webasto fire and the fan speed increase or decrease depending on the duty cycle, but if you want to test for longer than 5 minutes then you should ensure the engine is running on tickover.
When the test is running, always monitor the temperature via the measuring blocks to ensure you don't cook the Webasto.
Do NOT let the temperature rise above 90°, and if it gets close with the engine running, turn the heater on full heat and full fan to help dissipate residule heat.
Before running a self-test, run the Output Test and, once complete, check again for fault codes.
If any fault codes are logged you will need to repair and clear the codes before a self-test will function correctly.
To Run the Output test select controller 18 (additional Heater)
Then select Output Test
This will test the glow plug, dosing pump and air blower (Webasto internal fan).
To run a self-test select controller 18 (additional Heater)
Then select Basic Settings
When in Basic Setting select Group 022 and press Go.
Once this has been done the Webasto will fire (if it's functioning).
Switch to measuring blocks
Measure blocks 001, 002 and 003 to see voltage, temperature, cycle phase, etc.
To cancel the self test exit all screens and close the controller. This will place the controller into a phased shutdown which can take a couple of minutes to complete. The Webasto goes into a "cool down" and "burn-off" phase, so once there is no fuel being burned and the unit is cool it will shut down.
So don't worry when you still hear the Webasto running after you've exited all VCDS screens.
While testing you may notice a lot of white fumes and a strong smell of Diesel - it is normal - don't be alarmed, but it's always good to perform this test with the bonnet removed so you can act quickly should anything untoward occur.
Cheers
Jeff
