Code 129 — High Pressure Switch Open

What does 129 mean?

This fault indicates that the high-pressure safety switch has opened, signifying excessively high refrigerant pressure within the system. This causes a shutdown to prevent damage to the compressor.

• Blocked condenser coil (outdoor unit)
• Dirty air filter (indoor unit)
• Overcharged refrigerant system
• Malfunctioning outdoor fan
• Closed or blocked air vents

Click steps to track your progress.

1. 1

   Check and clean your air filters in the indoor unit.

2. 2

   Ensure the outdoor unit's coil is clean and free of debris, and the fan is spinning freely.

3. 3

   Verify that all supply and return air vents inside your home are open and unobstructed.

4. 4

   Turn off the HVAC system at the thermostat and then at the circuit breaker for 30 seconds, then restore power.

5. 5

   If the fault recurs, contact a qualified HVAC technician, as this involves refrigerant pressure and compressor health.