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Error code reference

Lennox Heat Pump Error Code 6

Compressor temperature exceeded its limit after running less than five minutes (or open sensor).

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What the 6 error code actually means

Your Lennox heat pump detected that its compressor got too hot within just the first few minutes of running, or the sensor that monitors that temperature has stopped working. The system shut itself down automatically to prevent serious damage to one of the most expensive components in the unit. A technician needs to inspect the temperature sensor and check the refrigerant levels before the system should be restarted.

Diagnostic procedure

The full 6 procedure

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1
First diagnostic step
Check compressor winding temperature sensors for open circuit.
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Most common causes of 6

Ranked by how often they cause this code
  1. 1Open compressor temperature sensor
  2. 2Corroded or loose sensor connector
  3. 3Low refrigerant charge
  4. 4Restricted refrigerant flow
  5. 5Failing or seized compressor

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Questions people ask about 6

What does 6 mean on a Lennox heat_pump?
Error code 6 on a Lennox heat pump means the compressor temperature exceeded its safe limit within five minutes of startup, or the compressor temperature sensor circuit is open. The control board shuts the compressor down immediately to prevent permanent damage. The two primary possibilities are a failed or disconnected sensor, and an actual overtemperature condition caused by refrigerant or compressor issues.
Is it safe to run my heat pump with error code 6 active?
No, you should not continue operating the system while this code is active. The error indicates a potential overtemperature condition that, if ignored, could permanently damage the compressor. The compressor is the most expensive component in the system, so allowing it to run in a fault condition is a significant financial and mechanical risk.
How much does it cost to repair error code 6 on a Lennox heat pump?
Repair costs vary widely depending on the cause. Replacing a compressor temperature sensor typically ranges from $75 to $250 including parts and labor. Refrigerant recharge or leak repair can range from $150 to $600 or more. Compressor replacement, if required, is significantly more expensive and can range from $1,200 to $2,800 or higher depending on the unit and labor rates in your area.
Will resetting the heat pump clear error code 6?
Resetting the unit may temporarily clear the fault and allow the system to attempt another startup cycle, but the code will return if the underlying cause is not corrected. If the sensor is open or the refrigerant charge is low, the protective lockout will trigger again. Resetting without diagnosis risks compressor damage and is not recommended as a long-term fix.
How do I fix error code 6 on a Lennox heat pump?
Begin by inspecting the compressor winding temperature sensor and its wiring harness for an open circuit using a multimeter. If the sensor and wiring are intact, have a licensed technician check refrigerant pressures and compressor performance. Depending on the root cause, repairs may involve replacing the sensor, correcting the refrigerant charge, or in worst-case scenarios, replacing the compressor.

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