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Error code reference

LG Hvac Error Code 49

13 SEER Split/Multi Split

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13 SEER Split/Multi Split: Outdoor unit discharge and air sensor both unplugged.

First step from the service manual

Verify AC voltage to ODU is 193-253V AC. If OK check fuses; if fuses OK, replace outdoor main PCB.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 49 means on a LG hvac

Error code 49 on LG 13 SEER Split and Multi Split systems indicates that both the outdoor unit discharge temperature sensor and the outdoor air temperature sensor have been detected as unplugged or disconnected simultaneously. These two sensors are critical inputs to the outdoor main PCB, which uses their readings to manage compressor operation, refrigerant flow control, and system protection logic. When both sensors go offline at the same time, the control board cannot safely regulate system operation and triggers this fault code.

The outdoor discharge sensor monitors the temperature of refrigerant leaving the compressor, while the outdoor air sensor provides ambient temperature data used for capacity calculations and defrost cycling. Losing both sensors together is a strong indicator of either a wiring harness fault, a connector issue at the PCB, or a failure of the outdoor main PCB itself. It is less likely that both individual sensors failed independently at the same moment, which points toward a shared wiring path or board-level fault.

Diagnosis should begin by confirming that AC supply voltage to the outdoor unit falls within the acceptable range of 193 to 253 volts AC. If input voltage is within spec, the next step is to inspect and test the outdoor unit fuses. If both voltage and fuses check out, the outdoor main PCB is the most likely failed component, as it may have lost the ability to read or power the sensor inputs correctly.

Source: manufacturer service documentation.

Common causes of 49

  1. 01

    Disconnected sensor connectors at outdoor PCB

    Wiring / connection

    Both the discharge and outdoor air sensor connectors may have come loose from the outdoor main PCB, especially after maintenance or vibration over time. Visually inspect all sensor harness connections at the board for loose or unseated plugs.

  2. 02

    Failed outdoor main PCB

    Part replacement

    If voltage and fuses are confirmed good but the error persists, the outdoor main PCB may have lost the ability to read sensor inputs due to internal component failure. Board replacement is required in this scenario.

  3. 03

    Damaged sensor wiring harness

    Part replacement

    The wiring harness shared by both sensors may be cut, pinched, or corroded, causing simultaneous signal loss. Trace the harness from the sensors to the PCB and look for visible damage or continuity breaks.

  4. 04

    Blown outdoor unit fuse

    Part replacement

    A blown fuse in the outdoor unit can interrupt power to sensor circuits, causing multiple sensor faults to appear together. Check all fuses in the outdoor unit fuse block after confirming supply voltage is within 193 to 253 volts AC.

  5. 05

    Low or incorrect supply voltage to outdoor unit

    Wiring / connection

    Supply voltage outside the 193 to 253 volt AC range can cause erratic PCB behavior including false sensor disconnection faults. Measure voltage at the outdoor unit disconnect before proceeding with any other diagnosis.

See the test procedure for each cause

Frequently asked questions about 49

What does 49 mean on a LG hvac?
Error code 49 on an LG 13 SEER Split or Multi Split system means the outdoor unit discharge temperature sensor and the outdoor air temperature sensor are both detected as unplugged or disconnected. The outdoor main PCB cannot operate the system safely without these inputs and shuts down. This fault typically points to a wiring issue or a failed outdoor main PCB.
Can I fix error code 49 on my LG mini split myself?
Some basic checks are within reach of a knowledgeable homeowner, such as verifying that no breakers have tripped and that the outdoor unit has power. However, safely measuring AC voltage at the outdoor unit, inspecting fuses, and diagnosing PCB-level faults requires electrical knowledge and the proper tools. Most repairs for this code, especially PCB replacement, are best left to a qualified HVAC technician.
Is it safe to run my LG air conditioner when error code 49 is showing?
No, you should not attempt to continue running the system while error code 49 is active. The system has shut down because it cannot monitor discharge and outdoor air temperatures, which are critical for protecting the compressor from damage. Continued operation without these sensor inputs could result in compressor failure or other serious damage.
How much does it cost to repair error code 49 on an LG split system?
Repair costs depend on the root cause. If the fix is simply reseating a loose connector, the cost may be limited to a service call fee, typically in the range of $75 to $150. If the outdoor main PCB needs to be replaced, parts and labor combined can range from $300 to $700 or more depending on the model and local labor rates.
Will resetting the unit clear error code 49 on my LG HVAC?
A power reset may temporarily clear the fault display, but the error code 49 will return if the underlying cause, such as a disconnected sensor harness or failed PCB, has not been corrected. Resetting without addressing the root cause does not fix the problem and could delay necessary repairs. A proper diagnosis should be performed before attempting to return the unit to service.

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