In this troubleshooting situation you have responded to a complaint that a 4-ton package unit air conditioner is not cooling. When you arrive, you find that the indoor air handler is running, the thermostat fan switch is set for AUTO, and a set-point of 75°F is selected. With the outdoor ambient at 98°, and the system not performing, the indoor air temperature is far above the comfort level.

When you check the equipment, you note that the outdoor fan motor is running normally. You also find that the compressor is hot to the touch and not running. When you check the wiring diagram and note the compressor wiring (see the partial diagram above), you disconnect the power supply and determine the following:

• Checking the C to HERM section of RC1 (run capacitor 1) shows a reading of 65 MFD.
   
• Testing at BK (black) and R (red) on the compressor wiring shows a resistance of 1.5Ω.
   
• Testing at BK (black) and PR (purple) on the compressor wiring shows a resistance of 2.0Ω.
   
• Testing at R (red) and PR (purple) on the compressor wiring shows a resistance of 3.5Ω.
   
• Testing all compressor terminals to ground shows infinity.

With the power restored you find that the compressor attempts to start but kicks off on overload.