Boondock

I've started having some odd AC trouble on my 2007 TL Type S.
The AC seems to work fine while driving around or even when in park. It blows cold and moving the temperature setting up and down does make the temperature (to my untrained hand) change.
However, as soon as I have to drive up a decent hill or grade, it seems like the AC stops blowing cold air.
This has happened while on the road on some decent inclines, but also in my work's parking garage ramps.
As for relative temperatures, I generally keep it set to about 70f in the car. Today in the morning it was in the low 80s (f) and this has also happened during the day when the temperature was in the mid to upper 90s over the last few days.
Any ideas as to what could be causing it to only have an issue while pointing up hill?

El_Cheapo

Maybe low on refrigerant.

csmeance

Change out your A/C Fan relay and compressor relay. Over time they can reduce power transmitted causing the fan/ compressor to not turn on intermittently. When the fan doesn't turn on, it's hard for the refrigerant to get to the right temp/pressure after the compressor does it's job and a/c system will warm up.

Relays are about $6 each at your local auto parts store. Being low on refrigerant could be an issue also as it does tend to slowly leak out over time. A local shop can check the pressure and see if it needs a minor top off. If you use one of the can's at the auto parts store, make sure you buy one WITHOUT THE STOP LEAK! Refrigerant ONLY.