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Error code reference

LG Hvac Error Code 25

Low voltage or high voltage feeding unit.

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Low voltage or high voltage feeding unit.

First step from the service manual

Verify proper 208/240V AC feeding unit; voltage feed must be 193-253V AC.

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

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What 25 means on a LG hvac

Error code 25 on an LG HVAC unit indicates that the supply voltage feeding the unit has fallen outside the acceptable operating range. The unit requires 208/240V AC single-phase power, and the acceptable voltage window is 193V AC on the low end to 253V AC on the high end. When the incoming voltage drops below 193V or rises above 253V, the control board detects the out-of-range condition and triggers this fault to protect the system from damage.

Low voltage conditions are more common than high voltage events and typically result from undersized wiring, loose connections at the disconnect or breaker panel, an overloaded electrical circuit, or utility supply issues. High voltage faults are less frequent but can occur during utility irregularities or if the unit has been connected to an incorrect power source. Either condition can cause compressor stress, control board instability, and premature component failure if left unaddressed.

The first diagnostic step is to measure the actual supply voltage at the unit's power terminals while the system is running under load, since voltage can appear acceptable at the breaker panel but sag significantly at the unit due to wiring resistance or loose terminations. A digital multimeter should be used to confirm the reading falls within the 193 to 253V AC range before attempting any other diagnostics.

Source: manufacturer service documentation.

Common causes of 25

  1. 01

    Low supply voltage due to undersized or degraded wiring

    Part replacement

    Wire gauge that is too small for the circuit run length causes voltage to drop under load. Check wire size and measure voltage at the unit terminals while the system is actively running.

  2. 02

    Loose or corroded electrical connections

    Wiring / connection

    Loose terminals at the disconnect box, breaker, or unit power block create resistance that causes voltage drop. Inspect and tighten all connections at the disconnect, panel, and unit terminals.

  3. 03

    Utility supply voltage outside acceptable range

    Wiring / connection

    The utility grid itself may be delivering low or high voltage to the property, which is outside the homeowner's control. Measure voltage at the main panel and contact the utility provider if readings are consistently out of range.

  4. 04

    Overloaded circuit shared with other high-draw appliances

    Part replacement

    If the HVAC circuit is shared with other large loads, simultaneous operation can pull voltage below 193V. Verify the unit is on a dedicated circuit sized for its rated amperage.

  5. 05

    Faulty or tripping breaker causing voltage irregularity

    Part replacement

    A breaker that is weak or partially tripped can deliver inconsistent voltage rather than cutting power completely. Test breaker output under load and replace if voltage is unstable or below spec.

See the test procedure for each cause

Frequently asked questions about 25

What does 25 mean on a LG hvac?
Error code 25 on an LG HVAC unit means the system has detected that the incoming supply voltage is outside the required operating range of 193 to 253V AC. The unit is designed to run on 208/240V AC, and anything below 193V or above 253V will trigger this fault. The system shuts down or faults out to prevent damage to the compressor and electronics. Restoring proper voltage is required to clear the error.
How do I fix error code 25 on my LG HVAC unit?
Start by measuring the actual supply voltage at the unit's power terminals with a multimeter while the system is under load. If voltage is below 193V, inspect for loose connections, undersized wiring, or a weak breaker. If the utility supply itself is out of range, contact your electric utility provider. Once the voltage issue is corrected and supply is confirmed within the 193 to 253V AC range, the unit should resume normal operation.
Is error code 25 on an LG HVAC a safety concern?
Yes, operating an HVAC system on out-of-range voltage poses real risks. Low voltage can cause the compressor motor to overheat and fail prematurely due to higher current draw. High voltage can damage the control board, capacitors, and other sensitive components. Addressing the voltage issue promptly protects both the equipment and the electrical system.
Will resetting the LG HVAC unit clear error code 25?
Resetting the unit may temporarily clear the fault display, but the error will return if the underlying voltage issue has not been corrected. The control board continuously monitors incoming voltage, so any reading outside 193 to 253V AC will re-trigger the fault. A reset is only a useful step after the supply voltage has been confirmed to be within the acceptable range.
How much does it cost to repair error code 25 on an LG HVAC unit?
The repair cost depends entirely on the root cause. If the fix involves tightening loose electrical connections, cost is minimal and may only require a service call fee in the range of $75 to $150. If new wiring or a dedicated circuit is needed, electrical work can range from $200 to $800 or more depending on the complexity. If the voltage fault has already damaged internal components like the control board or compressor, repair costs can increase substantially.

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