Noritz NR50, NR66 & NR71 Code 16
Abnormally high output temperature. The water leaving the unit is too hot. Noritz measures the resistance of the outlet thermistor and then checks for proportional gas valve trouble — one cause is a measurement problem, the other is the appliance really overfiring. Three flashes on an NR71 or N-0631S without a remote controller. This generation has no bypass or mixing valve to blame for an overshoot — the water servo codes 65 and 66 that later Noritz ranges carry do not exist on this table. That leaves the outlet sensor and the gas valve, which is exactly the two-cause list Noritz gives.
Also displayed as: 3 flashes
Call a proThe verdict
Call a licensed plumber
Turn the temperature down and treat scalding as a live risk until someone has looked. A proportional gas valve fault needs instruments, so the diagnosis is not a homeowner job even though the symptom is obvious.
Typical cost: $200–$900
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the NR50, NR66 & NR71 — not averaged across the brand.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 54), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Turn the set temperature down at the controller if you have one, and warn the household before anyone runs a tap.
- Call a licensed professional.
Code 16 on other Noritz series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: