Carrier Error Code 31: High Stage Pressure Fault

Severity
Warning
Type
led blink pattern
Where to look
sight glass
Estimated repair cost: $75 — $200 (parts + labor)
Warning: Your Carrier HVAC system has detected a high-pressure condition in the high stage of the compressor, which could lead to system damage. The system has likely locked out to protect itself.

LED Blink Pattern

3 short blinks, 1 long blink.

How to Fix Carrier Code 31

  1. Step 1: Turn off the HVAC system at the thermostat.
  2. Step 2: Inspect the outdoor unit for any obvious obstructions, such as leaves, debris, or snow, blocking airflow to the condenser coil. Clear away any obstructions.
  3. Step 3: Wait 30 minutes, then turn the system back on at the thermostat. If the error code reappears, contact a qualified HVAC technician for further diagnosis and repair.

How to Reset Carrier Code 31

  1. Turn off the furnace power switch, usually located on or near the unit.
  2. Turn off the circuit breaker for the furnace. Wait 30 seconds.
  3. Restore power at the breaker and flip the furnace switch back on.
  4. Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Carrier Error Code 31 Mean?

The Carrier error code 31, or a blinking LED pattern indicating code 31, signals that the system's high-pressure switch has tripped during high-stage operation. This switch is a safety device designed to shut down the compressor when the refrigerant pressure gets too high, preventing damage to the compressor and other components. The high-stage refers to when the unit is operating at its maximum cooling or heating capacity. This error usually means there's a restriction in the refrigerant flow, a problem with the compressor, or an issue with the outdoor fan motor. It's important to address this issue promptly to prevent further damage to your HVAC system. Because this code indicates a locked-out system, you will likely need a professional to diagnose and fix the root cause.

Common Causes

  • Dirty outdoor condenser coil restricting airflow.
  • Faulty high-pressure switch.
  • Refrigerant overcharge.
  • Failed or failing outdoor fan motor.
  • Restriction in the refrigerant lines (kinked or blocked).

Diagnostic Steps

If... Check Expected
System displays error code 31 Measure the refrigerant pressure using a manifold gauge set. Check both high and low side pressures. High-side pressure significantly above the normal operating range (typically above 400 PSI depending on refrigerant type and outdoor temperature).
High refrigerant pressure observed Inspect the outdoor condenser coil for dirt and debris. Clean the coil thoroughly. Pressure drops to normal operating range after cleaning.
Coil is clean, but high pressure persists Check the outdoor fan motor voltage and amperage draw. Voltage within +/- 10% of rated voltage, amperage within the motor's specified range. If voltage is good but amperage is low, the motor is likely failing.
Fan motor checks out Bypass the high-pressure switch. (CAUTION: Only for testing purposes and with extreme care). If the system runs normally with the switch bypassed, replace the high-pressure switch.

Applicable Carrier Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
High-Pressure Switch — — —
Outdoor Fan Motor HC39GE230A — Find Part
Condenser Coil — — —

Related Codes on Same Models

Other codes that affect the same Carrier model families as 31.

Code Description Severity
11 No Previous Error Info
12 Blower On After Power Up Warning
13 Limit/Rollout Fault Critical
14 Ignition Lockout Critical
21 Gas Heating Lockout Critical
22 Abnormal Flame Critical
23 Pressure Switch Fault Warning
32 Low Flame Sense Warning
33 Limit/Rollout Switch Lockout Critical
34 Ignition/Flame Sense Fault Warning