Read lots of posts re A/C issues, seems DCCV is pretty common. I have an issue when I turn the A/C on there is what appears to be a vacuum leak coming from in the dash. It is constant, if I leave the air on it will continue (the noise). It is not blowing hot air, it appears to be just blowing un treated air (same temp as outside). The A/C worked fine yesterday morning but has been doing this for two days now. Sounds similar to SmokinF1's problem, but I never get the transition from hot to cold.

Any suggestions would be much appreciated.

It could be a bad expansion valve, or maybe low R134. The first test to do is to check the high and low side pressures and compare them to the service pressure chart for your year LS. The climate control system on the LS (unlike most Ford cars) does not use vacuum at all.

Thanks Joegr, Ill test the pressures. Just fmi, what is that noise I hear in the dash that sounds sort of vacuum-ish?

Thanks Joegr, Ill test the pressures. Just fmi, what is that noise I hear in the dash that sounds sort of vacuum-ish?

I would assume (and you know what can happen when you assume) that it is the R134 flowing past the expansion valve.