1996 Volvo 960 Sometimes it works and sometimes it doesn't

When I start my car sometimes my air blows cold and will continue to blow cold throughout a trip. This may happen for a couple of start-ups and trips in a row; then, I will start up the car and the air blows the outside temperature and will continue to do so for a couple of trips.

I am not sure if this is related or not (it doesn't seem like it would be) but my brakes are also hissing when I press them and it seems like I am loosing my power brakes.