Sharp Air Conditioner: Common Inspection Methods for Control Circuits
(1) Check the power supply: This includes both the main power supply and the control circuit power supply.
(2) Check the signals: Signals in an air conditioner can be divided into two categories. The first category consists of control and protection signals, which include start/stop signals, temperature signals, motor signals, phase sequence signals, and pressure signals within the system. Among these, the start/stop signal controls the on/off state of the air conditioner; the temperature signal includes: ① freeze prevention and cold detection signals; ② temperature detection signals for the controlled area; ③ high-temperature exhaust detection signals. Additionally, there is a current signal used as a current detection signal for the control circuit to judge the working condition of the compressor. The phase sequence signal reflects the rotation direction of the compressor. Pressure signals include high-pressure and low-pressure protection signals. The second category consists of fault display signals.
(3) Check the load circuits in the detection circuit: Here, the loads refer to components such as the air conditioner's compressor, fan motors, four-way valves, and heating elements. These can be checked using conventional methods.
(4) Analyze the signal flow and identify the fault point: If necessary, certain signals can be simulated, for example, by using a light bulb as a dummy load (similar to repairing a color TV). This can help narrow down the fault range, reduce repair costs, and achieve twice the result with half the effort.
Beijing Sharp Air Conditioner Repair Center, August 10, 2011.