Side by side 2008 and 2015 xB A/C
 

So, it did seem like the refrigerant was a bit low in both of my xB's (2008 and 2015). A friend loaned me an A/C manifold and I picked up some R134a to take a look at it. Ambient temp is 80 deg F, turned both cars on at the same time parked side by side in the driveway. Turned A/C on to max ac, fan 4, drivers side window down, and temp gauge in the vents. Just idling both ended up down near 52 deg F and I went ahead and connected the manifold to the older 2008 one. The chart I saw for R134 showed for 80 deg F ambient something along the lines of 40-50psi low and 175-210psi high. I added refrigerant to each one so they are both right at the 210psi high, but the low is a bit odd. It likes to hang around 35psi instead of the 40-50psi. Both vents went down to 42 deg F and 44 deg F. Maybe 35psi is normal for the port location on these systems?

The issue I was having is that you would get into a hot car (happening a lot on the 2015, but I *think* it has happened once or twice on the 2008), turn the car on, ac max, start driving, but for the first 2-3 miles it does not act like the A/C is on at all. It blows burning hot air at you the entire time and no air temp cooling felt at all, then finally it will kick in and cool down. All the time it is on max ac, ac turned on. I have to wonder if something is keeping the system from coming on or something, what else in the system is there that might cause it so not run, but then all of a sudden begin to run. It seems to happen on the hottest days (100 deg F+), maybe driving cools down a sensor and it finally allows the A/C to kick on?

Check your condenser to see if it is dirty or blocked, it might not be getting enough airflow over it initially until you've driven for a bit, on top of the usual initial wait for cooling to start. Only thing I can think of.

It looks fine. I went ahead and tried to spray it off as much as I can from the small bottom vent in front.

I started both of them back up. No air - no fans running. I turned the AC on and immediately the fans came up, it blew out some of the water I sprayed into them. The newer one got cooler much faster because it was probably still warm from being driven 45 minutes earlier. In fact, when the fans kicked up in speed to cool the engine I noticed a huge difference in the A/C performance. It cooled considerably. On the 2008 when I turned it on and idled it, the fans were running slow (ac on), but it took much longer to warm up and turn on the engine cooling (fans much faster). During this time A/C was cool, but not cold at all. Again, once it warmed up and ran the fans faster, A/C cooled much better. It is possible that the A/C fan speed is just a bit slow?