Lennox Air Conditioner Error Code 5

Error code 5 means the pressure switch opened after the compressor had been running for more than two minutes. This tells the system that refrigerant pressures moved outside of safe operating limits during a run cycle. The most likely causes are low refrigerant charge or a blocked coil restricting airflow. The system shuts down to protect the compressor from running under damaging conditions.

No, you should not continue attempting to operate the system when this code is active. Running the compressor with low refrigerant charge can cause serious compressor damage due to inadequate lubrication and cooling of the compressor internals. The system is shutting down intentionally to prevent this damage, and repeated restarts without resolving the underlying cause can shorten the life of the compressor significantly.

Repair costs vary considerably depending on the root cause. A condenser coil cleaning is typically a lower-cost service call in the range of $75 to $200. If the system needs refrigerant, expect to pay for the service call plus the cost of refrigerant, which can range from $150 to $600 or more depending on refrigerant type and the amount needed. If there is a refrigerant leak requiring repair or a failed component such as a pressure switch or metering device, costs can range from $200 to $800 or higher depending on parts and labor in your area.

Some portions of the diagnosis are DIY-friendly, such as inspecting and cleaning the outdoor condenser coil for debris or checking that the indoor air filter is clean and unrestricted. However, checking refrigerant charge and repairing refrigerant leaks requires EPA Section 608 certification and proper gauging equipment, so those steps must be handled by a licensed HVAC technician.

Resetting the unit may temporarily clear the fault and allow the system to attempt another cycle, but the error will return if the underlying cause has not been addressed. If the issue is low refrigerant or a coil obstruction, the pressure switch will open again after the compressor runs for a couple of minutes. A reset is useful for confirming the fault is repeatable, but it is not a repair.