Error Code L1 in Air Conditioners: Meaning and Solution

The L1 error code in inverter air conditioning systems, common across most brands, indicates a voltage anomaly supplying the inverter module located on the electronic board of the outdoor unit. This error code is triggered as an overvoltage protection mechanism, signaling that the equipment is receiving voltage beyond the normal range, posing a risk to its internal components.

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Recommended Voltage Range

Most systems are designed to operate within a voltage range of 172 V to 260 V. If the voltage exceeds these limits, the system triggers the L1 error as a safety measure.

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Steps to Resolve the L1 Error

1. Turn Off the Equipment and Disconnect It from the Power Supply

Ensure the unit is completely powered off to safely proceed with diagnostics.

2. Check the Voltage of the Power Supply

• Use a multimeter set to the AC voltage range to measure the incoming voltage from the external power grid.
• If the voltage is excessively high, this is likely the cause of the error.

Solution: In areas with recurrent voltage issues, consider installing a voltage stabilizer to regulate the power supply, ensuring a stable and adequate voltage for the equipment.

3. Diagnose the Inverter Module

The inverter module converts alternating current (AC) to direct current (DC). Any significant voltage deviation can impact its operation.

a. Voltage Measurement in the Inverter Module:

• Connect the electronic board and measure the voltage at the P and N terminals of the inverter module:
  • In standby mode: ~310 V DC.
  • In operation: ~380 V DC.
• If the voltage exceeds these values, the L1 error will be triggered.

b. Check the Rectifier Bridge:

• Disconnect the electronic board from the power supply before performing measurements.
• Measure the resistance between any pair of terminals of the rectifier bridge.
  • If the resistance is close to 0, the rectifier bridge is defective and needs replacement.

DIODE TEST:

1. Set the multimeter to diode mode.
2. Place the red probe on the DC negative output terminal (Terminal 5) and the black probe on the AC input terminals (Terminals 1, 2, 3).
   • Voltage between Terminal 5 and Terminals 1, 2, and 3 should be approximately 0.378 V. A reading of 0 indicates failure.
3. Reverse the probes and repeat the test:
   • Between the DC positive output terminal (Terminal 4) and Terminals 1, 2, 3, the value should be infinite. A reading of 0 indicates failure.

If the rectifier bridge is damaged, it must be replaced.

4. Diagnose the Inverter System’s IPM Module

The IPM (Intelligent Power Module) manages the power supply to the compressor’s three coils.

Steps for Diagnosis:

1. Disconnect the unit from the power supply.
2. Discharge the capacitors using a multimeter set to the DC voltage scale.
3. Locate the IPM circuit:
   • It is covered by heat dissipation fins and connected to the compressor terminals via independent tracks.

a. Identify the Positive and Negative Inputs:

• Trace the tracks from the high-voltage capacitors to the IPM circuit.

b. Identify the UVW Outputs:

• Trace the tracks from the compressor connectors to the IPM circuit.

c. Diode Integrity Testing in the IPM:

• The IGBT transistors within the circuit have internal diodes that must be tested.

1. Set the multimeter to diode mode.
2. Place the black probe on the positive input of the IPM circuit and measure the U, V, and W points with the red probe:
   • Expected values: ~0.45 V for each measurement.
3. Reverse the probes and repeat the process for the negative inputs.

If any readings deviate from the expected values, the IPM module may be faulty and should be replaced.