LG Hvac Error Code 34

Error code 34 on an LG HVAC system indicates that the high pressure switch has opened due to refrigerant pressure exceeding 600 PSI on the high side of the refrigerant circuit. The high pressure switch is a safety device wired into the control circuit that trips and cuts compressor operation when system pressure rises to dangerous levels. This protects the compressor, refrigerant lines, and connected components from damage caused by excessive pressure. When the switch opens, the compressor shuts down and error code 34 is logged by the control board.

The most common reason for high side pressure to spike above 600 PSI is inadequate heat rejection at the outdoor condenser unit. If airflow across the condenser coil is blocked or restricted, the refrigerant cannot release heat efficiently, causing pressure to climb rapidly. Refrigerant overcharge is another frequent culprit, where excess refrigerant in the system raises operating pressures beyond normal design limits. A failed or underperforming condenser fan motor will produce the same result, as will a condenser coil that is fouled with debris, dirt, or biological growth.

In some cases, non-condensable gases such as air or nitrogen entering the refrigerant circuit can cause abnormally high discharge pressures even when refrigerant charge and airflow are otherwise acceptable. A failed expansion valve that restricts refrigerant flow can also create pressure imbalances. Technicians should measure both high and low side pressures, check condenser fan operation, inspect the coil for blockages, and verify refrigerant charge before suspecting the switch itself as a faulty component.