OK I have a 99 GC and the A/C ices up blowing warm air and I think the evaporator is icing up. You can see ice on A/C line @ receiver to firewall. If you shut A/C off for about 5 minutes it defrosts and works OK for while then ices again. Is the high or low pressure switch bad?

You can't really say that either of those switches are bad based on the evap iceing up. You'll need to put gauges on and check the pressures. Jeeps use an orifice tube and those generally don't have issues like this unless the tube is plugged up. Again, checking the pressures is the thing to do.