A/C cutoff switch?

[cuda6pak]

I drove to work this morning without the A/C on because it was pretty cool outside (70*). And I noticed it does the exact same thing as it does when I have the A/C on, it just starts dumping heat when I get to ~1.15 TPS or 3-5in/Hg. So it must not be the A/C cutting off, what bmackinnon mentioned sounds about right.