I also have a 98 SVT, 117,000 miles. Today I was on the toll road and when I had to stop for the toll line it got really hot really fast and it seemed the compressor was not kicking in. As soon as I got up to a cruising speed the cool air was there again, so mine seems the opposite of yours. It also seems like the compressor kicks in harder than it used to and I can feel it more often. Does this happen with you? Also, mine tends to start reving high while in neutral right beforethe cold disappears.
I did recharge it about a month ago and it seemed better, but now I don't think that was the problem. When it kicks in it is still cold. Seems like the compressor maybe. My mechanically inclined father suggested cleaning the throtle position sensor with "Seafoam". Again, not sure if the compressor and idle speed are related, but they happen at the same time. I am going to try the cleaner first.
Are you having any idle speed issue also?
