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Error code reference

LG Air Conditioner Error Code E191

No temperature changes in EVA OUT during pipe inspection or changes in temperature seen in indoor unit with wrong address.

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What the E191 error code actually means

Your LG air conditioner ran a self-check and could not confirm that refrigerant is flowing properly through one of the indoor units, or it detected that the wrong indoor unit responded during the check. This usually means there is a sensor problem, a refrigerant flow issue, or the indoor units have been set up with incorrect identification numbers. A technician will need to inspect the system wiring, unit addresses, and refrigerant circuit to resolve this.

Diagnostic procedure

The full E191 procedure

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1
Confirm the fault
Power cycle the unit: switch off the breaker for 60 seconds, then restore power. If the code returns, the fault is persistent and the procedure below isolates the cause.
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Most common causes of E191

Ranked by how often they cause this code
  1. 1Incorrect indoor unit address assignment
  2. 2Faulty or disconnected EVA OUT thermistor
  3. 3Refrigerant restriction or insufficient charge
  4. 4Communication wiring miswiring between units
  5. 5Defective indoor unit PCB

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Questions people ask about E191

What does E191 mean on a LG air_conditioner?
E191 indicates a failure during the pipe inspection routine, which is an automated check the system runs to verify refrigerant flow through each indoor unit. The fault triggers when no temperature change is detected at the evaporator outlet (EVA OUT) sensor, or when a temperature change is seen in an indoor unit with the wrong address. This points to sensor issues, refrigerant flow problems, or incorrect unit addressing in a multi-zone setup.
Is it safe to run my LG air conditioner with the E191 error showing?
Operating the system with E191 active is not recommended. The error indicates that the system cannot confirm proper refrigerant distribution, which means one or more indoor units may not be cooling or heating correctly. Continued operation under these conditions could stress the compressor or other components and may worsen an underlying refrigerant or electrical issue.
How much does it cost to repair an E191 error on an LG air conditioner?
Repair costs vary depending on the root cause. Correcting an address configuration error is primarily a labor charge and may fall in the range of $75 to $150. Replacing a thermistor or repairing wiring could cost $150 to $350 including parts and labor. Refrigerant-related repairs, such as fixing a restriction or recharging the system, typically run $200 to $600 or more depending on system size and refrigerant type.
Can I fix E191 on my LG air conditioner myself?
Some causes of E191, such as incorrect address settings on the indoor unit, can be corrected without special tools by verifying and adjusting DIP switch or software address configurations. However, diagnosing refrigerant flow issues, testing thermistors, or repairing communication wiring typically requires a qualified technician with the proper diagnostic equipment. Refrigerant handling also requires EPA certification.
Will resetting my LG air conditioner clear the E191 error?
A power reset may temporarily clear the fault display, but if the underlying cause is not corrected, the error will return when the system runs the pipe inspection sequence again. Persistent E191 errors require proper diagnosis of the address configuration, EVA OUT thermistor, refrigerant circuit, and communication wiring rather than simple resets.

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