Noritz tankless water heater code 73
Circuit board setting fault. Code 73 means the same thing on all 5 Noritz series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code 73 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| EZ Series & NCC199CDV | Circuit board setting fault | Call a pro | $100–$800 |
| NCC199 & NRC111 | Circuit board setting fault | Call a pro | $100–$800 |
| NR50, NR66 & NR71 | Circuit board setting fault | Call a pro | $100–$800 |
| NR98 & NR111 | Circuit board setting fault | Call a pro | $100–$800 |
| NRC Series | Circuit board setting fault | Call a pro | $100–$800 |
Each row opens the full page for that generation. We hold manuals for EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71, NR98 & NR111 and NRC Series, and each one gets its own reading of code 73 — what Noritz documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 5 series in four columns, which is enough to route you and not enough to explain anything. This is the Noritz wording behind each row, one entry per manual, so you can see where the 5 readings of code 73 agree and where they part company.
EZ Series & NCC199CDV — Circuit board setting fault
The board's configuration is wrong or has just been changed. Noritz checks the maintenance writers, the board itself for damage, and the DIP switch settings — giving exhaust type and vent length as the examples. The remark explains the most common trigger: this error is displayed when switching the dip switch with the power on.
NCC199 & NRC111 — Circuit board setting fault
The board's configuration is wrong or has been changed. Noritz checks the maintenance writers, the board for damage, the DIP switch, and the "control switch connector" — giving the high elevation connector as the example. Elevation and vent settings determine how the appliance burns gas, so these are combustion settings rather than preferences.
NR50, NR66 & NR71 — Circuit board setting fault
The board's configuration is wrong or has been changed. Noritz checks the maintenance writers, the board for damage, the DIP switch and the "control switch connector", giving the high elevation connector as the example. Elevation settings determine how the appliance burns gas. Five flashes on an NR71 or N-0631S with no remote controller. Older units get moved. This code shows up after a board swap or a change of altitude or venting, and on a range this age the person who last set those switches is often long gone — which makes the installation paperwork, if it exists, more useful than the code.
NR98 & NR111 — Circuit board setting fault
The board's configuration is wrong or has been changed. Noritz checks the maintenance writers, the board for damage, the DIP switch, and the "control switch connector" — giving the high elevation connector as the example. Elevation and vent settings determine how the appliance burns gas, so these are combustion settings rather than preferences. This one follows board work more often on this range than on any other Noritz table, because the same board covers seventeen model numbers across residential and commercial ASME units. The settings that tell it which one it is in are exactly what this code reports.
NRC Series — Circuit board setting fault
The board's configuration is wrong or has been changed. Noritz splits this into three display-window codes: 731 is the maintenance writers set incorrectly, 733 is the DIP switch settings — Noritz gives high elevation and vent length as the examples — and 734 is circuit board failure. The vent length and elevation settings tell the appliance how hard to run its fan, which is why this is a combustion setting and not a preference.
Does it matter which Noritz you have?
EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71, NR98 & NR111 and NRC Series all route code 73 the same way: a professional, at $100–$800. That makes it one of the Noritz numbers you can act on before working out which unit you own.
What to check first, whatever your series
These checks are on the manufacturer's list for every Noritz series that reports code 73, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Call a licensed professional.
That is 1 of the 3 checks documented for code 73. The rest differ by generation, so if none of those explains it, go to your own series above.
Which Noritz do you have?
On the 5 series that report code 73, the model number on the rating label starts EZ, NCC, GQ, N and NRC — match yours against the 43 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Noritz Service Manual — NRC663 FSV, EZ98DV, EZ111DV, NCC199CDV (Rev. Oct 2017) (p. 32), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 55), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
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 Noritz range.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 56), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
Source: Noritz Service Manual — NR501-OD, NR662-OD, NRC661, NRC711 (Rev. Dec 2013) (p. 28), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
The same number on other brands
Code 73 is not a standard across the industry — every manufacturer publishes its own table. If your unit is not a Noritz, this number means something else entirely:
Parts, guides and symptoms behind code 73
Code 73 on these 5 Noritz series points at 1 part and 2 symptoms, each named by the manufacturer's own procedure for this code.