LG Heat Pump Error Code 35

Error code 35 means the compressor shut off due to low suction pressure three times within one hour. The control board tracks these low pressure events and locks out the unit after the third occurrence to protect the compressor. Common causes include a refrigerant leak, a closed service valve, or a faulty low pressure sensor. A technician should inspect and diagnose the system before restarting it.

The unit should not be forced to run while this fault is active. Low suction pressure can cause the compressor to operate without adequate refrigerant lubrication, which leads to overheating and potentially permanent compressor failure. The system is designed to lock out under these conditions for good reason, and continued operation attempts can significantly increase repair costs.

Repair costs vary widely depending on the root cause. If the issue is simply an improperly closed service valve, the cost is minimal and limited to a service call fee, typically in the range of $75 to $150. Refrigerant leak detection and recharge can run $200 to $600 or more depending on the type of refrigerant and severity of the leak. Replacing a low pressure sensor typically falls in the $150 to $350 range including parts and labor, while a failed expansion device or filter drier repair can range from $300 to $700.

Some basic checks, like confirming the service valve is fully open and inspecting the coils for ice or debris, can be performed without special tools. However, diagnosing a refrigerant leak, recharging the system, or replacing a low pressure sensor requires EPA certification and specialized equipment. Most homeowners should contact a qualified HVAC technician to resolve this fault safely and correctly.

A power reset may temporarily clear the fault and allow the unit to attempt to restart, but if the underlying cause is not repaired, the low pressure condition will return and the error will be triggered again. Because the code requires three compressor shutdowns in one hour to set, repeated resets without a fix will continue to damage the compressor over time. A proper diagnosis and repair of the root cause is necessary for a lasting resolution.