Analysis and Repair: Based on the fault symptoms, it was determined that there were issues with the wiring of the line control board and peripheral components of the microprocessor. Measurements showed that transistors VT8 and VT15 were functioning properly. Under power, the voltage at pin 33 of IC 6805R was measured while pressing the power button, but no change in voltage was observed. This indicates that either VT8 or VT15 is not operating correctly. Further checks revealed that the emitter (e) of VT15 has a +5V voltage relative to ground. Upon inspecting the diode connected in series with the switch, it was found that neither the anode nor cathode terminals were conducting.
Model: Chunlan KFR-25GW air conditioner, remote control not functioning.
Source: Beijing Chunlan Air Conditioner Repair http://chunlankt120.blog.163.com/.
Fault Symptoms: After powering on and pressing the remote control switch, the entire system fails to start or run normally, though it can be forcibly started.
Repair Method: The issue was resolved by replacing the faulty diode with one of the same model.