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Rheem · Heat pump

90 Communication fault

Medium severity Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

What the control is telling you

Listed as 'Communication Fault' but the manual's description says the ICC has detected an internal fault and should be replaced - manual inconsistency.

Applies to: (-)PRL-JEC 2-stage 16 SEER heat pumps: RPRL/UPRL-024JEC, -036JEC, -048JEC, -060JEC

Likely causes

  • Communication wiring problem (1/2 data wires)
  • ICC internal fault

Test and repair steps

  1. Check data wires 1 and 2, R and C at the thermostat, indoor and outdoor units - reversed comm wires keep the green comm LED (D52) on solid.
  2. Check term/bus dip switches on the ICC and air handler (term switches ON).
  3. Never use phone cord or connect the system to a phone line.
  4. If wiring is correct, replace the ICC (move the memory card to the new board).

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Source: Rheem (-)PRL-JEC Heat Pump Installation Instructions, 12.6 ICC Diagnostic Codes, p.30. 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.