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Carrier · Air conditioner

84 High pressure lockout (4 hours)

High severity Carrier Infinity 19VS 24VNA9Carrier 2-stage 24ANB/25HNB

What the control is telling you

Amber STATUS light flashes 84. The high pressure switch kept opening and the unit could not stage down any further (elevated from code 31). 4-hour lockout. Type: System malfunction; reset: 4 hours.

Applies to: Carrier Infinity 19VS variable speed air conditioner 24VNA9 (AOC control + inverter)

Likely causes

  • Outdoor airflow too low or off / dirty or iced coil
  • Overcharged system or indoor TXV problem
  • Restriction in circuits or tubing
  • Service valve left closed
  • Loose HPS harness or HPS unplugged from the inverter
  • Restricted filter drier
  • Non-condensables in the system
  • Faulty pressure switch

Test and repair steps

  1. Check and clean the outdoor coil and fan (cooling).
  2. Cooling check subcooling in Charging Mode (or the subcooling chart on the control box door) and adjust charge.
  3. Make sure both service valves are open.
  4. Check the HPS harness, pins and its connection to the inverter.
  5. Check for a temperature drop across the filter drier.
  6. Non-condensables recover, replace the drier, evacuate and recharge.
  7. If discharge pressure on a gauge is below about 600 psig (±20) while the switch reads open, replace the pressure switch.
  8. Troubleshoot the TXV.

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Source: Carrier 25VNA8 / 24VNA9 Service Manual, Table 6 Fault Code Actions, p.24. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.