Lennox Air Conditioner Error Code 6

Error code 6 on a Lennox air conditioner means the compressor temperature exceeded its allowable limit within the first five minutes of running, or the compressor temperature sensor circuit is open. The system shuts down automatically to protect the compressor from damage. The fault points to either a sensor or wiring problem, a refrigerant system issue driving high superheat, or restricted airflow.

No. Error code 6 causes the system to shut the compressor down as a protective measure, and attempting to force the unit to run with this condition present risks permanent compressor damage. The compressor is the most expensive component in the system, so operating through this fault is not advisable until the underlying cause is diagnosed and corrected.

Repair costs vary significantly depending on the cause. Replacing a faulty compressor temperature sensor typically falls in the range of $100 to $300 including labor. Refrigerant recharge or metering device replacement can range from $200 to $600 or more depending on refrigerant type and system size. If the compressor itself has been damaged by overheating, replacement costs can range from $1,200 to $2,800 or higher, making early diagnosis important.

Some steps, such as replacing the air filter, clearing obstructions from return air vents, and visually inspecting sensor wiring for obvious damage, can be done without specialized tools. However, checking refrigerant pressures, measuring superheat, and testing thermistor resistance require a manifold gauge set and a multimeter, and any refrigerant work requires EPA 608 certification. Most repairs beyond basic airflow checks should be handled by a licensed HVAC technician.

A power reset may temporarily clear the code and allow the unit to attempt another run cycle, but if the underlying cause is still present, the fault will return within the first five minutes of operation. Resetting without diagnosing and fixing the root cause can accelerate wear on the compressor. The fault should be fully investigated before relying on a reset as a solution.