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Error code reference

LG Hvac Error Code 33

Single speed compressor discharge pipe temperature 105°C/220°F or higher.

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Single speed compressor discharge pipe temperature 105°C/220°F or higher.

First step from the service manual

Verify proper refrigerant charge & ensure unit is not in high-head temperature situation. Generally undercharge. Check discharge pipe thermistor: 244,000Ω at 20°C/68°F, 24,400Ω at 90°C/194°F.

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

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What 33 means on a LG hvac

Error code 33 on an LG single-speed compressor system indicates that the discharge pipe temperature has reached or exceeded 105°C (220°F). The discharge pipe thermistor monitors the temperature of the refrigerant gas leaving the compressor. When this temperature climbs too high, it signals that the compressor is working under extreme stress conditions, which can degrade compressor oil, damage internal windings, and ultimately lead to compressor failure if left unaddressed.

The most frequent root cause of this error is an undercharged refrigerant system. When refrigerant levels are low, the compressor must work harder to move heat, and the discharge gas temperature rises significantly as a result. Other contributing factors include restricted airflow across the outdoor coil, a failed or failing condenser fan, a dirty coil reducing heat rejection, or non-condensable gases in the refrigerant circuit. Any condition that creates a high-head pressure situation will drive discharge temperatures upward.

Diagnosis should begin with verifying the refrigerant charge and checking system pressures. The discharge pipe thermistor itself should also be tested for accuracy. At 20°C (68°F) the thermistor should read approximately 244,000 ohms, and at 90°C (194°F) it should read approximately 24,400 ohms. A thermistor reading outside these values at known temperatures indicates a faulty sensor that may be triggering a false fault. Correct refrigerant charge and rule out airflow restrictions before replacing the thermistor.

Source: manufacturer service documentation.

Common causes of 33

  1. 01

    Low Refrigerant Charge

    Wiring / connection

    An undercharged system is the most common trigger for error 33. Low refrigerant causes the compressor to overheat as it strains to maintain system pressures. Check system operating pressures and look for signs of a refrigerant leak before recharging.

  2. 02

    Restricted or Reduced Airflow Across Outdoor Coil

    Wiring / connection

    A dirty condenser coil, blocked unit clearance, or a failed condenser fan motor reduces the system's ability to reject heat, driving discharge temperatures into fault range. Inspect and clean the outdoor coil and confirm the fan is operating at the correct speed.

  3. 03

    Faulty Discharge Pipe Thermistor

    Part replacement

    A thermistor that has drifted out of specification can report falsely elevated temperatures and trigger error 33 even when actual discharge temps are normal. Test resistance at a known temperature: the sensor should read approximately 244,000 ohms at 20°C and 24,400 ohms at 90°C. Any significant deviation indicates a bad sensor.

  4. 04

    Non-Condensable Gases in the Refrigerant Circuit

    Wiring / connection

    Air or moisture contamination in the refrigerant circuit raises condensing pressure and discharge temperature. This condition typically appears after an improper refrigerant service and requires recovering the charge, evacuating the system, and recharging with clean refrigerant.

  5. 05

    Refrigerant Metering Device or TXV Restriction

    Part replacement

    A partially blocked expansion valve or metering device can cause abnormal pressure ratios that increase discharge superheat and drive up compressor discharge temperatures. Check subcooling and superheat values to identify this condition.

See the test procedure for each cause

Frequently asked questions about 33

What does 33 mean on a LG hvac?
Error code 33 on an LG HVAC system means the discharge pipe temperature on the single-speed compressor has reached or exceeded 105°C (220°F). This is a protective shutdown to prevent compressor damage. The most common cause is low refrigerant charge, though high-head pressure conditions from restricted airflow or a faulty thermistor can also trigger this fault.
Can I fix error code 33 myself?
Some basic checks are within reach for a knowledgeable DIYer, such as inspecting the outdoor unit for blocked airflow, cleaning a dirty condenser coil, and confirming the condenser fan is running. However, checking refrigerant charge and testing the discharge thermistor with an ohmmeter require technical skill and, in the case of refrigerant handling, EPA certification. If the system is low on refrigerant, a licensed HVAC technician is needed to find the leak, repair it, and recharge the system properly.
Is it safe to keep running my LG HVAC when error code 33 appears?
No, you should not continue operating the system while this fault is active. Sustained high discharge temperatures can break down compressor lubricant, damage compressor valves, and lead to complete compressor failure. The system's protective shutdown is working as intended, and operating through it risks turning a refrigerant or sensor issue into a much more costly compressor replacement.
How much does it cost to repair error code 33 on an LG HVAC?
Repair cost depends heavily on the root cause. A refrigerant leak repair and recharge can range from roughly $200 to $600 or more depending on leak location and refrigerant type. Replacing a discharge pipe thermistor is generally less expensive, typically in the $75 to $200 range including labor. Condenser coil cleaning is usually the least costly service. If the compressor has already sustained damage from prolonged overheating, costs rise significantly.
Will resetting the unit clear error code 33?
A reset may clear the fault code temporarily and allow the system to restart, but the error will return if the underlying problem is not corrected. If the discharge temperature exceeds 105°C again, the system will shut down again. Resetting without diagnosing and fixing the cause, whether low refrigerant, airflow restriction, or a faulty thermistor, only delays the repair and risks further damage to the compressor.

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