If the ac is not working correctly, as you stated that when on highways it blows warm air, check out the actuators. It could be that one of the actuators, that controls outside/inside air mixutre (I think that this actuator exists) is not functioning properly.

As to the noise, are you sure it is not the interior temp pump that is making the noise? As I mentioned, I had the same noise, it would start a few seconds after start up and it was intermitant.

Iggy

__________________
Insanity: doing the same thing over and over again and expecting different results.

2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
1994 - Yamaha WaveRaider (fun to ride)