Ok, I just found this thread. My XKR is doing exactly as the OP described. Turning on the 'DEFROST' option, or going into the climate options screen and selecting the windscreen icon does NOT activate the system to blow air out of the windscreen vents. I can hear the fans going but no air physically comes out of the upper vents.

If I press the face level vents icon, the system will open something and the air comes quite forcibly out of the face vents.

Pressing the icon to return to windscreen mode turns off the air to the face vents but still nothing comes out of the windscreen vents.

So this morning and this evening I've had to drive off with the screen all fogged up. At work this evening I even had to get a credit card out and 'scrape' the inside of the screen just to clear the water off the inside of the screen, it wasn't just a fog, but actual droplets on the inside of the screen. I sat there for 5 minutes trying to get some air flow up the screen before giving up.

Drove away and 2 minutes later I heard the windscreen vents finally open and the screen was cleared within 30 seconds.

Using the defrost button does everything as stated... except allow any air to physically exit the windscreen vents.

I suspect sticky upper vents, has anyone else actually had this issue and successfully resolved it?

 

Chiming in that I have this exact same behavior from my 2012. This is my first winter with the car, so it seems strange to me.

I hear the fan blowing air, but nothing coming out of the windshield vents. Suddenly after a few minutes of driving with a foggy windshield, the vents open and the fog clears up in seconds. It's a bit frustrating.

It really does seem like the car is looking for a temp reading from a sensor before it opens the windshield vents, for some reason. No codes or faults, so I'm not sure what's going on.

Based on what I'm reading here, it's normal? At the very least, a few of us are having the same issues.

 

Are you setting the controls properly? Did you manually select recirculate inside air? If so, that could cause fogging in cold weather. Have you read your Owner's Handbook? If not,

 

Quite literally JUST pressing the defrost button after starting the car... Are you implying I should/shouldn't be doing something besides that to remove fog from the windshield? The manual even states that everything should happen automatically regarding AC, recirculation, fan speed, etc.

As stated, everything works... It just takes a few frustrating minutes for the windshield vents to open and clear the fog.

 

My 2007 XK used to blow air to the screen on DEFROST immediately from startup - my 2014 XK doesn't. The front and rear heated screens come on immediately and I can hear the heater fan running but air output doesn't start until engine temperature begins to rise. I assume this is a design feature of climate control on later cars so ice cold air doesn't blow from the vents on frosty mornings.

Graham

 

I have the same flaw in my 2010. No air is physically directed to the windshield, regardless of any auto or manual operation of the climate controls.
Timing is about 10 minutes before the airflow is finally diverted to the glass.

My '07 XK works flawlessly, so I know "normal operation" does not do this.

I have not dug deeper yet, but the comments about a possible blender valve or direct pressure sensing valve may be closer to the truth, certainly not operator error.
One part that may attribute to the problem is that my AC is also not as good as the XK (takes longer to generate cold air, and does not get as cold overall in comparison). AC is used as a dehumidifier during defrost, so it could be a contributing factor....

 

I will say that my air conditioning also takes a bit to start blowing cold air in the summer... so this could be directly related to an AC system pressure issue.

If it takes awhile for refrigerant pressure to increase enough to overcome the low pressure switch and start the compressor, this could also be happening in the winter. It's possible that the defrost is waiting for the AC compressor to kick on before opening the windshield vents, and a low pressure reading is causing the delay.

That's purely hypothetical, however. It could be verified by watching the air conditioning module on an OBD reader. If the windshield vents open immediately when the ac compressor value flips to "on", I think we'd have a winner for diagnosis. Fix the AC delay issue, and the defrost issue should also be resolved.