Coupe GT A/C Isssues

[David]

First, let me say that I refilled the AC last Thursday. It was low causing the compressor to cycle very frequently. I only have a low side guage, so I really don't know what the pressures for the high side look like, but the low side pressure seemed OK after filling and vent temps were nice and cold, temps drop down to about 34.5*F then the compressor kicks out, then raise to about 37*F then it kicks back in. 

OK, yesterday was about the hottest day of the year. It was the upper 90s here with heat indexes above 110*F.  I was out for lunch and the AC was rockin, vent temps below 40*F even on a #3 blow. Stop at Sonic, eat lunch while it's idling witht he AC on...vent temps are exactly where they should be. Drive on to 7-11. Turn off car go in and grab smokes. Come out...start car...and no AC. Drive to the hsoue (3 blocks) and begin to troubleshoot (in a suit & tie no less). Compressor is not kicking in at all. System was just refilled last week, so it is unlikely it is just totally out of refridgerant. I checked every fuse and relay that had anything to do with AC. I even swapped the AC relay with another one (same rating/kind). No luck. Checkded the flapper valve on the airbox, opening closing slowly. I hear a sucking sound from around the ISV and discover a split in the lower hose. But that shouldn't have anything to do with AC, right? Car is somewhat hard to start due to vacuum leak, and idle hunts once engine is in closed loop. All this is expected behavior given the 1.5" split in the ISV hose. Can't find the problem. At this point I'm hot, sweaty and pissed...I pack up and leave. Just outide my driveay I romp on the gas and rev her up to the redline (or close to it) in frustration & anger...guess what? The AC kicks in. Vent temps plumit downto 50*F rapidly and eventually hit 40*F on the drive back to work. Just for shits & giggles, I turn off the AC for a second and hit the switch to turn it back on...NO AC AGAIN! But ut worked fine on the drive home and worked fine this morning on the drive to work. WTF? Thoughts? Would a vacuum leak have anything to do with this? Or my recent refill?

Dave 
1987 CGT 2.3
SE VA