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Carrier · Heat pump

83 Low pressure lockout (4 hours)

High severity Carrier Infinity 18VS 25VNA8Carrier 2-stage 24ANB/25HNBCarrier single-stage communicating HP

What the control is telling you

Amber STATUS light flashes 83. Suction pressure dropped below the no-operation level 3 times (elevated from code 32). 4-hour lockout. Type: System malfunction; reset: 4 hours.

Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8 (AOC control + inverter)

Likely causes

  • Service valve left closed
  • Cooling: Undercharged system
  • Cooling: Indoor airflow too low or off / iced coil
  • Cooling: Restriction in circuits or tubing
  • Heating: EXV malfunction
  • Heating: Outdoor airflow too low or off / iced coil
  • Heating: Undercharged system
  • Restricted filter drier
  • Expansion device restriction (TXV on short line sets under 15 ft)

Test and repair steps

  1. Make sure both service valves are fully open.
  2. Cooling check subcooling in Charging Mode (or the subcooling chart on the control box door) and adjust charge (add charge if low).
  3. Check indoor coil, filter and blower (cooling) and outdoor coil and fan (heating); de-ice if needed.
  4. Heating compare pressures with the heating check chart; if they do not match, recover, evacuate and weigh in the rating plate charge.
  5. Check for a temperature drop across the filter drier and replace it if restricted.
  6. Troubleshoot the EXV and TXV; repair any tubing restriction.

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Source: Carrier 25VNA8 / 24VNA9 Service Manual, Table 6 Fault Code Actions, p.23. 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.