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Error code reference

LG Hvac Error Code 73

Inverter compressor drawing over 48 amps.

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Inverter compressor drawing over 48 amps.

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What 73 means on a LG hvac

Error code 73 on an LG inverter HVAC system indicates that the inverter compressor is drawing more than 48 amps of current. This is an overcurrent protection fault. The inverter drive board continuously monitors the compressor's current draw, and when the measured amperage exceeds the 48-amp threshold, the system shuts down to prevent damage to the compressor windings, power transistors, and associated drive circuitry. This protection exists because sustained overcurrent conditions generate excessive heat and can rapidly destroy inverter components.

The inverter compressor in an LG system is a variable-speed motor controlled by a DC inverter drive board. Under normal operating conditions, the compressor draws current within a specific range depending on load and speed. When current spikes above 48 amps, the fault is typically rooted in one of several areas: a mechanically seized or restricted compressor, a failed inverter drive board producing unregulated output, compromised compressor motor windings causing a short circuit, or refrigerant system conditions such as severe overcharge or liquid slugging that increase the mechanical load on the compressor.

Diagnosing this fault requires measuring compressor winding resistance across all three terminals to check for shorts or opens, inspecting the inverter drive board for burned components or failed IGBTs, and evaluating refrigerant pressures to rule out system-side causes. A compressor that is mechanically seized will typically show correct winding resistance but will not spin freely. A shorted winding will show resistance imbalance or near-zero resistance between terminals. Both conditions will produce the overcurrent fault at startup or during operation.

Source: manufacturer service documentation.

Common causes of 73

  1. 01

    Mechanically seized or failing compressor

    Part replacement

    A compressor that is struggling to turn due to internal mechanical failure draws excessive current at startup. This is often accompanied by unusual noises or a compressor that hums but does not start.

  2. 02

    Failed or damaged inverter drive board

    Part replacement

    A faulty inverter board may output unregulated voltage or current to the compressor, causing the compressor to draw far more amperage than normal. Inspect the board for burned traces, failed IGBTs, or bulging capacitors.

  3. 03

    Shorted compressor motor windings

    Part replacement

    Internal winding insulation breakdown causes a short circuit within the compressor motor, dramatically increasing current draw. Measure resistance across all three compressor terminals to identify imbalance or a near-zero reading.

  4. 04

    Refrigerant overcharge or liquid slugging

    Wiring / connection

    Excessive refrigerant or liquid refrigerant entering the compressor increases mechanical load significantly, causing elevated current draw. Check system pressures and look for signs of refrigerant flooding at the suction line.

  5. 05

    Blocked or restricted refrigerant flow

    Wiring / connection

    A clogged filter drier, kinked line, or failed expansion device can create abnormal pressure differentials that force the compressor to work harder and draw more current. Inspect system pressures and refrigerant circuit components.

See the test procedure for each cause

Frequently asked questions about 73

What does 73 mean on a LG hvac?
Error code 73 on an LG HVAC system means the inverter compressor has been detected drawing more than 48 amps of electrical current. The system shuts down automatically to protect the compressor, inverter board, and wiring from heat damage. This is a serious fault that typically points to a failing compressor or a problem with the inverter drive board. A qualified technician should diagnose the system before it is restarted.
Can I fix error code 73 on my LG HVAC myself?
Most causes of error code 73 involve high-voltage electrical components and refrigerant systems that require licensed technicians to service safely. Diagnosing the fault requires specialized tools such as a clamp meter, resistance measurement equipment, and refrigerant gauges. Homeowners should not attempt to open the electrical enclosure or handle refrigerant lines. Calling a certified HVAC technician is the appropriate course of action.
Is error code 73 on an LG HVAC dangerous?
The error itself is a safety response, meaning the system has already shut down to prevent a more serious failure. However, the underlying condition that caused the overcurrent, such as a shorted compressor or a faulty inverter board, does present an electrical hazard if the system is repeatedly restarted without proper diagnosis. Do not continue to reset and restart the unit, as doing so can worsen the damage and create additional safety risks.
Will resetting the system clear error code 73 on my LG HVAC?
Resetting the system may temporarily clear the fault and allow the unit to attempt a restart, but if the root cause has not been corrected, the overcurrent condition will return and the error will reappear, often very quickly. Repeated restarts without resolving the underlying problem can cause additional damage to the inverter board and compressor. A reset is not a repair and should only be done as part of a proper diagnostic process.
How much does it cost to repair error code 73 on an LG HVAC?
Repair costs vary widely depending on the root cause. An inverter drive board replacement typically ranges from a few hundred dollars to over a thousand dollars including labor. Compressor replacement is the most expensive outcome, often ranging from several hundred to several thousand dollars depending on the system size and labor involved. Refrigerant system corrections such as removing an overcharge are generally less costly. A technician's diagnostic visit is needed to determine which component is at fault before an accurate estimate can be provided.

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