Lennox Heat Pump Error Code 5

Error code 5 on a Lennox heat pump means that the low-pressure or high-pressure safety switch opened after the compressor had been running for more than two minutes. This indicates the refrigerant circuit is operating outside of normal pressure limits. The most common causes are an improper refrigerant charge or a blocked indoor or outdoor coil restricting airflow.

No, you should not continue running the unit while this error is active. The pressure switches are designed to protect the compressor from operating under damaging conditions. Repeated compressor starts under low or excessively high pressure can cause permanent compressor damage, which is one of the most expensive components in the system to replace. Leave the system off until the underlying cause has been identified and corrected.

Resetting the unit may temporarily clear the fault and allow the system to restart, but the error code will return once the compressor has run for more than two minutes if the underlying pressure problem has not been corrected. A reset is useful for confirming the fault is repeatable, but it is not a repair. Continued resets without addressing the root cause risk damaging the compressor over time.

Some steps are DIY-friendly, such as replacing a dirty air filter, cleaning debris from the outdoor coil, and making sure vents are not blocked inside the home. However, diagnosing and correcting refrigerant charge issues requires EPA certification and manifold gauge equipment, so that portion of the repair must be handled by a licensed HVAC technician. Attempting to add or remove refrigerant without proper training and tools can make the problem worse and is regulated by federal law.

Repair costs vary widely depending on the root cause. A coil cleaning service typically runs in the range of $100 to $250. Refrigerant recharge costs depend on the refrigerant type and the amount needed, commonly ranging from $150 to $500 or more. If the compressor has been damaged due to prolonged low-pressure operation, replacement costs can range from $1,200 to $2,500 or higher depending on the unit size and model.