HVACopediaNoritz · Tankless water heater
65 Main water control servo abnormality
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
- Descale the unit and clean the inlet filter; the decks list 65 among hard water codes.
- Turn off power and check the main servo connector and wiring.
- Run Trial Operation for the water servo (EZ Start Plus app) where available.
- 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.
- Remove the servo and look for debris or scale; clean or replace the servo.
Settings for these units
Indoor clearances (required and recommended) · Noritz NRCR
| Location | Required | Recommended (service) |
|---|---|---|
| Top | 12 in. (300 mm) | 3 in. (76 mm) above and below exhaust |
| Front | 4 in. (100 mm) | 24 in. (610 mm) |
| Sides | 3 in. (76 mm) | 8 in. (203 mm) |
Required clearances apply to both combustible and non-combustible materials.
Recommended space is for service and quick access to gas and water shut-offs.
Operation panel menu settings and defaults · Noritz EZ, Noritz NRCR
| Setting | Options | Default |
|---|---|---|
| Max Set Temperature (power off) | 100-140 F in 5 F steps; 37-48 C, 50-60 C | 120 F / 50 C |
| Recirc ON/OFF | ON / OFF | OFF |
| Recirc Mode | Always OFF, Always ON, Manual Timer, Auto Learning (NRCR) | Always OFF |
| Vacation Mode | Active / Inactive | Inactive |
| Flow Meter Alarm | 10-60 gal (5 gal steps), 70-100 gal (10 gal steps), OFF | Alarm OFF |
| Drain Water (power off) | Start / Cancel | Cancel |
| Scale Flushing (power off) | Start / Cancel | Cancel |
| Audible Alarm | ON / OFF | ON |
| Screen Lock | Active / Inactive (4-digit password) | Inactive |
| Units (first 10 min after power-up, power off) | [F/gal/ft] or [C/L/m] | [F/gal/ft] |
| Power Saving Dis. / Backlight | ON-OFF / Power Save ON-OFF | ON / Power Save ON |
| Brightness / Contrast / Touch Sound | Bright-Normal-Dim-Dark / -15 to +15 / ON-OFF | Normal / Standard / ON |
Setting 125 F (55 C) or higher needs Max Set Temperature raised first; the panel warns about scald risk.
Default Settings resets everything in Settings except Screen Lock (hold OK about 5 s).
- Water quality limits · Noritz EZ, Noritz NRCR
Models that show this code
12 models in Noritz EZ, Noritz NRCR, Noritz CDV, Noritz NRC/NRCP
Other codes on the same units
- 29 Condensate collector water level abnormal
- 061 Recirculation abnormality (sub-code of 06)
- 062 Recirculation abnormality (sub-code of 06)
- 63 Recirculation abnormality (no recirculation flow)
- 66 Bypass water control servo abnormality
- 73 Circuit board setting abnormality
- 90 Combustion abnormality
- 91 Gas conversion not done correctly
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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.