I came form an 03 Passat that had a Climatronic heating/cooling system( Which BTW out performs the TL one) and in the 4 winters I had it I seldom had to use the windshield defrost mode and when I did it reacted very well.

The only adjustments I made in the Passat were from 69 in the summer to 72 in the winter and it just took care of buisiness. The TL doesn't. Maybe the Passat had better interior temp sensor location I don't know.

Anyway back to the original question. The TL seems to fog up a lot more on the inside and I have to manually go to the defrost button to clear the windshield. If I just go to the "Mode" button and set it to the first setting which shows defrost and the down arrow the defost doesn't keep up. The car is dry inside as are the matts.

In the Auto mode does it recirculate all the time? I know in the Passat it made adjustments all the time and wouldn't even got o high fan untill it had the required warm or cold air to supply to alter the temp. In other words on a hot day when you get in a hot car it wouldn't blast you with hot air .. it would come up to high fan when the A/C had cold air to supply. Same with warming the car in winter.

 

The auto mode does wait until the system is ready to properly cool, Unless you push the Defrost button, then it will just start spitting air to clear the windshield as quickly as possible.

Does that help answer your question

 

Forget about the mode button.... if you're having trouble with the defrost, don't direct the airflow anywhere except to the windshield for the first while until it has had a chance to not only clear the mist on the inside of the window, but has had a chance to slightly warm the windshield to inhibit the condensation of water vapor also. Also, try adjusting the temperature upwards a bit to facilitate this, and then you can most likely go back to fully automatic mode. Hope this helps...

TL42 - Gord