Fault Handling Document for Temperature Sensor of HY_M050 Variable Frequency Multifunctional Heat Pump

1. Fault Types and Corresponding Codes

According to the product manual, temperature sensor faults cover multiple types of sensors, with corresponding fault codes and trigger logic as follows:

2. Causes of Faults

1. Faults of Sensors Themselves

• Sensor component aging: After long-term use, core components such as thermistors experience performance degradation, unable to collect temperature signals accurately.
• Physical damage to sensors: Sensors are squeezed or pulled during installation or maintenance, leading to component cracking and lead fracture.
• Sensor water ingress and moisture: The sealing rubber ring fails, allowing water vapor to enter the sensor and causing short circuit or signal drift.

2. Connection Line Faults

• Loose wiring: Terminal connections between the sensor and the main control board become loose due to vibration or long-term use, resulting in poor contact.
• Damaged wiring: The wiring is scratched by sharp parts or scorched by high-temperature components, causing internal copper wire breakage or insulation layer damage and short circuit.
• Line interference: Sensor wiring runs parallel to high-voltage lines, causing signal abnormality due to electromagnetic interference.

3. Main Control Board Faults

• Damage to the main control board's collection port: Circuit components of the port are burned out, unable to receive analog signals from the sensor.
• Abnormal main control board program: Program bugs lead to misjudgment of sensor signals and false fault codes.

3. Fault Troubleshooting Steps

Step 1: Confirm Fault Codes

1. Check the wire controller or unit display, record the current fault code, and determine the type of faulty sensor by referring to the above fault type table.
2. If the code is not related to temperature sensors, troubleshoot other faults first before checking temperature sensors.

Step 2: Inspect Sensor Appearance and Wiring

1. Inspect the sensor itself:
   • Locate the installation position of the corresponding sensor (e.g., next to the outdoor unit fins, on the water tank side wall, on the inlet and outlet pipes, etc.), and check whether the sensor housing is cracked or deformed and whether the sealing rubber ring is intact.
   • Gently pull the sensor lead to check for loosening or fracture.
2. Check wiring continuity:
   • Cut off the unit's power supply, use the resistance range of a multimeter to measure the resistance value between the two ends of the sensor lead:
     • At room temperature (around 25℃), the resistance value of the temperature sensor is usually between 5kΩ and 10kΩ (refer to the product specifications for details). If the resistance value is 0 (short circuit) or infinite (open circuit), the sensor itself is faulty.
     • If the sensor resistance value is normal, continue to measure the continuity between the sensor lead and the corresponding terminal of the main control board. If there is no continuity, there is a break in the wiring.
3. Check line interference:
   • Observe whether the sensor wiring is bundled with or runs in parallel with the compressor power line or fan high-voltage line at a distance less than 10cm. If so, mark it as a suspected interference source.

Step 3: Inspect the Main Control Board and Program

1. Test port voltage:
   • Power on the unit (pay attention to safety to avoid electric shock), use the voltage range of a multimeter to measure the supply voltage of the corresponding sensor port on the main control board (usually 5V or 12V).
   • If the supply voltage is abnormal, the port circuit of the main control board is faulty; if the voltage is normal, proceed to the next step.
2. Verify program parameters:
   • Enter the unit parameter setting interface to check whether the parameters related to sensor faults (such as P32 and P63) are set correctly:
     • For suction temperature sensor faults, confirm the value of parameter P32; for DHW tank temperature sensor faults, confirm the value of parameter P63. If the parameter setting is incorrect, adjust the parameter first and observe whether the fault is eliminated.

Step 4: Cross-Validation Troubleshooting

1. If the sensor itself is suspected to be faulty, replace it with a spare sensor of the same model, connect it, and test it by powering on the unit. If the fault code disappears, the original sensor is damaged.
2. If the main control board port is suspected to be faulty, connect a normal sensor to the faulty port. If the fault is still reported, the main control board port is damaged; if the fault disappears, the original sensor or wiring is faulty.

4. Fault Handling Solutions

1. Handling Faults of Sensors Themselves

• Replace the temperature sensor with one of the same model and specification: Apply sealant during installation to ensure a good seal between the sensor and the installation position to prevent water ingress; tighten the fixing screws to prevent loosening due to vibration.
• For sensors that are aging but not completely damaged, if no spare parts are available temporarily, they can be calibrated temporarily (only for emergency use): Compensate for the temperature deviation of the sensor by adjusting the main control board parameters, but replace them with official parts as soon as possible.

2. Handling Connection Line Faults

• Loose wiring: Re-tighten the terminal connections, and wrap waterproof tape around the terminals if necessary to prevent oxidation and loosening.
• Damaged wiring:
  • If the damaged position is close to the sensor, cut off the damaged section, re-solder the lead, and wrap it with insulating tape;
  • If the wiring is severely damaged, replace the entire sensor cable directly. When routing the cable, avoid high-voltage lines and high-temperature components, and keep a distance of ≥10cm from high-voltage lines.
• Line interference: Adjust the routing direction of the sensor wiring, and keep a vertical angle when crossing high-voltage lines; or cover the sensor wiring with a metal shielding tube to reduce electromagnetic interference.

3. Handling Main Control Board Faults

• Port circuit fault: If the port components are damaged, replace the corresponding components (such as capacitors and resistors); if the port chip is damaged, replace the entire main control board.
• Abnormal program: Contact the manufacturer to obtain the latest program, and upgrade the main control board program using a dedicated programmer; restart the unit after upgrading and observe whether the fault is eliminated.

4. Verification After Fault Recovery

1. After fault handling is completed, power on the unit and check whether the fault code disappears. Enter the unit parameter interface to check whether the temperature displayed by the corresponding sensor is normal (the deviation from the actual environment/medium temperature is ≤±2℃).
2. For the special situation where both inlet and outlet water sensors are faulty:
   • In A/C mode: After repairing any one of the sensors, the unit will automatically switch to the normal antifreeze logic;
   • In DHW mode: After repairing the DHW sensor, the unit will automatically switch to the normal antifreeze logic.
3. Run the unit continuously for more than 2 hours to confirm that there is no re-alarm and all functions (antifreeze, defrosting, heating/cooling, etc.) operate normally.

5. Emergency Handling in Special Scenarios

During temperature sensor faults, the unit will trigger special antifreeze logic. Pay attention to the following emergency operations:

1. Simultaneous faults of inlet and outlet water sensors (A/C mode):
   • When the outdoor ambient temperature <5℃ or the outdoor temperature sensor is faulty, the unit will automatically start pump C1 for antifreeze; if there is an auxiliary pump C3, C3 will participate in antifreeze simultaneously.
   • Emergency handling: Prioritize repairing any one of the temperature sensors to restore the normal antifreeze logic; if immediate repair is not possible, ensure the pump runs continuously to prevent pipeline freezing and cracking.
2. DHW sensor fault (DHW mode):
   • When the outdoor ambient temperature <5℃ or the outdoor temperature sensor is faulty, the unit will automatically start pump C1 for antifreeze; if there is an auxiliary pump C3, C3 will participate in antifreeze simultaneously.
   • Emergency handling: Repair the DHW tank temperature sensor as soon as possible. If immediate repair is not possible, check the temperature of the water tank and pipelines regularly to avoid freezing damage.