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Error code reference

LG Hvac Error Code 29

Inverter compressor high amperage.

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Inverter compressor high amperage.

First step from the service manual

Verify proper 208/240V AC feeding unit, ensure not in high-head pressure condition, verify 3 compressor windings all equal at 1-4Ω, verify ∞Ω to ground, check amperage.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What 29 means on a LG hvac

Error code 29 on an LG inverter-driven HVAC system indicates the inverter compressor is drawing excessive amperage during operation. The inverter drive board monitors current draw from the variable-speed compressor continuously, and when amperage exceeds the acceptable threshold, this fault is triggered to protect both the compressor and the drive electronics. This is a protective shutdown, not a nuisance trip, and the underlying cause must be identified before the system is restarted.

High amperage conditions in an inverter compressor typically stem from one of three categories: electrical supply problems, mechanical load problems, or compressor winding faults. On the electrical side, low or unbalanced supply voltage at 208/240V AC forces the compressor to draw more current to maintain its output, so verifying proper voltage at the unit under load is a critical first step. High-head pressure conditions, caused by a dirty condenser, refrigerant overcharge, or non-condensables in the system, increase the mechanical load on the compressor and directly raise current draw.

On the compressor itself, winding resistance should be checked across all three terminals. Each winding should measure equally in the 1 to 4 ohm range, and resistance from any winding terminal to ground should read infinite (open circuit). A winding-to-ground fault or unequal winding resistance indicates internal compressor failure. If windings test within spec and voltage is confirmed correct, the inverter drive board itself may be misreading current or failing to regulate output frequency properly, making the drive board a secondary suspect after the compressor and system pressures are ruled out.

Source: manufacturer service documentation.

Common causes of 29

  1. 01

    High refrigerant head pressure

    Wiring / connection

    A dirty condenser coil, blocked airflow around the outdoor unit, refrigerant overcharge, or non-condensables in the system increase the compressor's mechanical load and cause current to spike. Inspect the condenser coil for debris and check system pressures with manifold gauges.

  2. 02

    Low or incorrect supply voltage

    Wiring / connection

    The unit requires a stable 208/240V AC supply. Low voltage forces the compressor to draw higher amperage to compensate, triggering this fault. Measure voltage at the unit's disconnect under operating load to confirm it is within spec.

  3. 03

    Compressor winding fault

    Part replacement

    If any of the three compressor windings reads outside the 1 to 4 ohm range, reads unequal compared to the others, or shows measurable resistance to ground instead of infinite resistance, the compressor has an internal failure and requires replacement.

  4. 04

    Failed or faulty inverter drive board

    Part replacement

    If supply voltage, system pressures, and compressor windings all test within specification, the inverter board may be delivering incorrect frequency or voltage to the compressor or inaccurately sensing current. The drive board is the secondary suspect after other causes are ruled out.

  5. 05

    Compressor seized or mechanically binding

    Part replacement

    A compressor that is beginning to seize internally will draw extremely high locked-rotor or near-locked-rotor current even if windings test correctly on a static resistance check. Abnormally high amperage confirmed with a clamp meter during a start attempt points to this condition.

See the test procedure for each cause

Frequently asked questions about 29

What does 29 mean on a LG hvac?
Error code 29 on an LG HVAC system indicates the inverter compressor is drawing excessive amperage. The system shuts down automatically to protect the compressor and the inverter drive electronics. Common causes include high head pressure, incorrect supply voltage, and compressor winding faults. A technician should diagnose the root cause before restarting the unit.
Can I fix error code 29 on my LG HVAC myself?
Some preliminary checks, such as clearing debris from the outdoor condenser coil and verifying the unit's circuit breaker is the correct size, can be done by a homeowner. However, checking supply voltage under load, measuring refrigerant pressures, and testing compressor winding resistance require proper tools and training. Most repairs that address code 29 should be handled by a licensed HVAC technician.
Is it safe to keep running my LG HVAC when error code 29 appears?
No. Error code 29 is a protective shutdown, meaning the system has already stopped the compressor to prevent damage. Repeatedly resetting and restarting the unit without resolving the cause can permanently damage the compressor or the inverter drive board. The system should remain off until a technician identifies and corrects the underlying issue.
How much does it cost to repair error code 29 on an LG HVAC?
Repair costs vary widely depending on the root cause. If the issue is simply a dirty condenser or a voltage supply correction, costs may be minimal, typically in the range of a standard service call fee of $75 to $150. Inverter drive board replacement can range from $300 to $700 depending on the model. Compressor replacement is the most expensive outcome, often ranging from $800 to $2,000 or more including labor.
Will resetting the unit clear error code 29 on a LG HVAC?
A power reset may temporarily clear the fault and allow the unit to restart, but if the underlying cause is still present, the system will detect high amperage again and the code will return. Resetting without repair is not a solution and risks worsening the damage to the compressor or drive board. The fault should be fully diagnosed before the unit is returned to service.

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