1996 Saab 9000 4-cylinder turbo, factory R134a system with Sanden SD7H15 compressor. This system uses a block-style expansion valve that does not have an external bulb. Several years ago the compressor, condenser, pusher fan, hoses, drier, pressure sensors, and expansion valve were replaced. It's an ACC setup with the heater core always in the loop, outlet temperature controlled by a mixer flap.
What's happening this summer is that cooling performance is poor, air is cool rather than cold under most conditions. On a hot sunny day at idle the outlet air will turn warm. Cooling is adequate only when outside temperature is below about 80 degrees and there is little or no sun. This is all with the compressor clutch engaged. Pressures at idle are about 30 psi low, 250 psi high at an ambient temperature of about 85 degrees. The condenser looks clean and the pusher fan and radiator fan work OK. Temperature mixing flap appears to be working.
Any suggestions of further diagnostics or the likely cause of the problem?