High pressure switch open. The unit steps down capacity for each occurrence and elevates to fault 84 if it happens on the lowest stage. Reset time is 6 minutes, then the unit runs at a reduced stage.
Homeowner part this code names: AC coil cleaner.
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Bryant outdoor 31 means the high pressure switch opened. The unit steps down a stage for each occurrence and elevates to fault 84 when that happens on the lowest stage. Reset time is 6 minutes, then reduced-stage operation. Reduced capacity clears after 2 hours of continuous running at any stage. Table 6 says to use the fault 84 checks. Furnace code 31 is the high-heat pressure switch inside the furnace, a different fault.
Same characters, different appliance: Bryant 31 on a furnace is a different fault. Bryant furnace 31.
Likely causes
- The service manual points code 31 at the fault 84 cause list
- Outdoor airflow too low or off, including a coil blocked by ice or debris
- Overcharge, a closed service valve, or a restriction in the filter drier, EXV, TXV, or tubing
- Loose high-pressure-switch harness, or the switch disconnected from the inverter
- Faulty pressure switch, or the reversing valve stuck in cooling during a heating call
Safe checks for 31
- With the disconnect and the breaker off, check the outdoor coil for ice or debris and clear it if you can do that without opening the electrical panel
- Technicianfollow the fault 84 table for charge, service valves, the filter drier, the expansion device, and the pressure-switch harness
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
Call a licensed HVAC technician if 31 repeats or becomes 84. The 6-minute reset is not a repair.
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Parts & tools for this fix
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AC and heat pump coil cleaning supplies: guide
In this code: Outdoor airflow too low or off, including a coil blocked by ice or debris
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