В мануале на Миллению (KL, KF), по-мимо всяких прочих давлений и т.д, описан еще и вот такой способ оценки производительности.
Думаю, что это может относиться не только к этим двигателям и может быть поможет вам
REFRIGERANT SYSTEM PERFORMANCE TEST
1. Perform refrigerant pressure check. (See REFRIGERANT PRESSURE CHECK .)
l If it is correct, go to step 2.
l If not as specified, troubleshoot the refrigerant system. (See TROUBLESHOOTING
INDEX .)
2. Install the manifold gauge set. (See Manifold Gauge Set Installation .)
3. Open the hood.
4. Close all the doors and all the windows.
5. Warm up the engine and run it at a constant 1,500 rpm .
6. Turn the AUTO switch on.
7. Set the temperature setting dial to 18.0°C {65°F} .
8. Wait until the air conditioner output temperature stabilizes. The output temperature is stable
when the A/C compressor is repeatedly turned on and off based on the A/C compressor control
of the A/C amplifier.
9. Record center ventilator left side temperature.
10. Determine and record ambient temperature.
11. Verify that the temperature reading is in the shaded zone.
l If the performance is not within the shaded zone, troubleshoot the refrigerant system.