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Noritz · Tankless water heater

65 Main water control servo abnormality

Medium severity Noritz EZNoritz NRCRNoritz CDVNoritz NRC/NRCP

What the control is telling you

The board cannot communicate with or position the main water flow control servo. Same meaning on all families; hard water and scale are a listed cause.

Applies to: All Noritz residential tankless (EZ, NRCR, NCC199CDV, NRC/NRCP)

Likely causes

  • Scale or debris in the main servo
  • Failed servo motor
  • Wiring/connector fault
  • Circuit board fault

Test and repair steps

  1. Descale the unit and clean the inlet filter; the decks list 65 among hard water codes.
  2. Turn off power and check the main servo connector and wiring.
  3. Run Trial Operation for the water servo (EZ Start Plus app) where available.
  4. NRC/NRCP water route at set temp 120 F or lower both main and bypass are open; at 125 F or higher bypass closes and main stays open.
  5. Remove the servo and look for debris or scale; clean or replace the servo.

Settings for these units

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Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), 65 & 66 error codes, p.15; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), Water control route and 65 & 66 error codes, p.3-4, 9; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Poor water quality issues, p.32. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.