BMW 525i (1994) sedan Automatic T, 145000 mi.
Air conditioner works when engine speed is low but cuts out and blows hot air when speed reaches approx 2500 rpm. Temp guage does not read hot. Aux fan has been replaced, coolant checked, compressor not leaking, pressure valve has been changed.
Any ideas?

please tell me what the high and low side pressures are.
does the magnetic clutch stay coupled when the problem occurs?