2000 Acura RL Air Conditioner

The air conditioner on my 2000 Acura RL 3.5 blows cold air while it is idling and at low speeds but when at highway speed it cuts out pumping warm air. The Acura dealer technician ran it for 45 minutes and it maintained a low temperature so they declared it operational with no problem. I took it back out onto the highway and the same scenario took place. So I took it back. They found that the cabin air filters under the glove box were extremely clogged. They replaced them and diagnosed it saying that the heater control valve would not close all the way allowing hot water(antifreeze) coolant from the engine cooling system into the heater core counteracting the air-conditioned coolant air flow to the passenger cabin. They said they topped of the antifreeze and coolant gas ( 134a)since they saw some bubbles in the viewing window. This did not correct the problem. So they reemphasized that the hot water shut off valve was the problem.
I didn’t buy this prognosis so I disengaged the hot water valve to the heater preventing any hot engine coolant into the heater. The same thing happened. The air conditioner produces very cold air while idling and speeds up to 40 mile per hour then cut out. The fans seem to be working properly I then set the car in park and increased the RPM’s to 2500 up to 4000 RPM’s to simulate highway driving. The electromagnetic clutch on the compressor disengaged causing the blower to produce hot air again. Then I disconnected the compressor low pressure switch coming off the condenser which is attached with the drier viewing window and I connected a jumper wire to bypass the switch. The clutch reengaged but then shut off after a few minutes. I could not locate the relay switch to test it. Can anyone help me? Can this model operate if it has low or too much coolant gas? Could it be electrical?