Heater faulty after coolant change ,2018 tiguan 2.0 litre 132kw CZPA

[Darvidge]

Iv`e done a coolant change on my Tiguan and my heater now is playing up. I`m not sure if it happened since coolant change , or possibly been like this prior. My heater works perfectly on high heat setting, but turned down just one click to 29.5 or lower, it stops blowing heat. At one time it was producing some reduced heat at 26 - 29.5 , but not now. I have run the system with tank lid off with engine hot , heater flat out , for extended period to bleed the system, but heater still not operating properly. Car temp sitting perfect on extened drive . I have done the climatronic re- calibration a number of times with little success. I can only suspect air mix flaps are faulty, as at full heat the sound is distinct compared to turning it down only one or two cicks to 29, the sound has a distinctly different sound like it it shutting off heat mode completely ,which it is literally doing. Any ideas on this problem?

[Lucas_R]

Modern engines really need to be vacuum filled when doing a coolant change, and while doing it, you need to have the ignition on with the heater set to max temp and a slow/medium fan speed to open the heater core so that it fills with coolant.

Highly likely that you have a pocket of air in your heater core and this is why it is only working in certain situations.

Your best bet would be to drop the coolant back out into a clean container so you can pour it back in, this time with the ignition on and heater set to max temp and low fan speed to open the heater core.

[Darvidge]

Thanks Lucas, air in the system is possible and probable, and I`ll be addressing that after I sort out the problem Iv`e just proven .In my first post on this , I mentioned the change from HI to only one increment down to 29.5 or lower is very distinct . I have taken the side cover off console and observed the shaft linkage going from full heat to full shutoff after only that half degree down from full heat, where it should be incremental with every temp` adjustment This action is identical to the climatronic recalibration, as I obseved while the console side cover was off. Just to repeat, I have full heat on HI , but constantly full shut off with only one click down in temp`. Any input will be great.