Noritz Tankless Water Heater Not Working
The Short Answer: A Noritz that will not heat is four folders: no 120 V, no flow call, a lockout code, or freeze/gas. Photograph the remote or PCB digits before you kill power. Do not vinegar-flush a dark controller. Ice-cold with water still moving is not the same job as no water flow. Code 11 is ignition failure.
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Search Intent & The Real Problem
Every hot tap is ice. Not slow. Not lukewarm. Cold. The internet said “reset it” and “descale with vinegar.” Resetting an NRC, EZ, NR, NRCP, or NCC that never fires glazes the igniter. Descaling a unit that has no 120 V, a closed isolation valve, or a packed inlet screen does nothing except flood a mixer. Sister hubs: Rinnai no hot water, Takagi problems. A puddle under the cabinet is Noritz leaking from the bottom — shut it down first.
What other guides get wrong
They paste a Rinnai 10 (air/exhaust) onto a Noritz. Noritz does not use 10 the same way — fan and combustion faults land on 61 / 90 / 99. They treat every dead Noritz as scale. Scale is 14 / 16. They send you at a manometer. They skip the isolation handles left 45° after a “handyman flush,” so you buy a board for two closed ball valves. And they tell you to crank the remote to 140°F. A dead burner does not care about setpoint.
Step-by-Step Troubleshooting
Step 1: Split power, flow, lockout, and “it fires but the tap is cold”
| What you have | Folder | Next |
|---|---|---|
| Blank remote, no PCB LED | Power / GFCI / disconnect | Step 2 |
| Display On, no fire, no code | No flow call | Isolation, inlet screen, min GPM |
| Two-digit code on remote or 7-seg | Lockout | Photograph; use that digit |
| Fan runs, spark, then 11 | Ignition failure | Code 11 |
| Lit, then 12 | Flame lost after light | Rod, wind, gas — licensed if it repeats |
| Flame on, outlet hot, fixture cold | Mixing valve / crossover | Thermometer |
| After a storm, freeze, or outage | Rain / ice / GFCI | After rain |
- What to look for: Closest hot faucet as the test, not the master shower 60 feet away. Rating plate: NRC1111, EZ98/EZ111, NR66/NR71/NR83/NR98, NRCP recirc, NCC commercial, Quick-Connect pair.
- Required tools: Phone photo of the code and the plate. No wrenches.
Lukewarm that never hits setpoint is undersize, scale, or mix — not this ice-cold page. Hot-then-cold mid-shower is often min-flow: tankless goes hot to cold.
Step 2: 120 V — GFCI, disconnect, freeze circuit
- What to look for: Outdoor GFCI popped. Disconnect off. House breaker off. Remote unplugged so the pad is dead while the PCB still has power. Freeze-protection on outdoor NR/NRC needs unswitched power — a switched “energy saver” is how those exchangers split at 15°F. Reset a GFCI once. If it trips again, leave it off. A breaker that will not reset is a short, not a Noritz menu.
- Required tools: Eyes, receptacle tester. Cover stays on until the switch is off.
A wet PCB from condensate overflow or a freeze-split is power-off, water isolated — not a reset. Same physics as Navien condensate.
Step 3: Call for heat — valves, screen, activation flow
- What to look for: Blue/red service-valve handles not parallel to the pipe. Both cold and hot isolation must be open. Cylindrical cold-side inlet screen packed with sand, Teflon, or solder — brand-new installs do this. Fixture mixing below activation (often ~0.4–0.5 GPM on residential Noritz). Recirc return closed on an NRCP. Quick-Connect secondary isolated so only one box can fire.
- Required tools: Hands on the handles. Isolation off, faucet relieved, then rinse the screen. Bucket.
If hot taps are bone dry with valves open, stay on no water flow. If water moves and In-Use / burner never starts, you have a flow-sensor or board job — do not jumper the sensor.
Step 4: Read the Noritz code — not a Rinnai chart
Confirm your door sticker. Typical residential map:
| Code | Meaning | First split |
|---|---|---|
| 11 | Ignition failure — no proven flame | Gas cock, igniter — that page |
| 12 | Flame lost after it lit | Rod, wind, low gas |
| 13 | Remaining flame — valve not closing | Shut gas. Leave. Not a reset. |
| 14 | Thermal fuse / overheat | Scale, blocked exchanger |
| 16 | Outlet too hot | Scale, starved flow, failed mixer |
| 31 / 32 | Inlet / outlet thermistor | Unplugged probe, scale on the sensor |
| 61 / 99 | Fan motor | Silent fan = CO if anything burns — do not fire it |
| 71 / 72 | Gas solenoid / flame-sense circuit | Licensed |
| 90 | Abnormal combustion | Vent, gas quality, licensed |
| 76 | Remote communication | Cable, pad, then board |
- What to look for: One power cycle after the obvious cause (cock parallel, cap clear, LP not frozen, screen rinsed). Same digit on the next shower is the end of DIY. A bang on a late light is delayed ignition — loud bang — shut it down.
- Required tools: Jacket sticker. No manometer. NG ~3.5–7 in. w.c. / LP ~10–11 in. w.c. is licensed — confirm the rating plate. Do not purge the line. No gas at other appliances is not getting gas, not a PCB.
Step 5: Freeze, rain, and when the cabinet is already wet
- What to look for: Outdoor unit after a 15°F night with power off: ice in the waterway or a split exchanger. Do not torch it. Restore freeze-protection power or wait. Rain in an outdoor burner after a missing cap is dead after rain, same family as a Rinnai after an outage — after power outage. Water inside the jacket with fittings dry is often the exchanger — isolate. Condensing NRC/EZ with a trap full will wet the pan and take the board; that is plumbing, then a licensed look at the PCB.
- Required tools: Freeze history, paper towel. Need it dark while you wait? Shutoff.
Do not set 140°F to chase a mixer. Do not hold a tripped breaker On.
When DIY Ends: Calling a Licensed Pro
You may restore one GFCI, turn the remote On, rinse the inlet screen, open isolation valves, photograph a code, and power-cycle once. Stop at gas odor, a wet cabinet, a silent fan, a freeze-split, a 13, a repeating 11/12/90, and any jumper. Combustion, gas pressure, flame rod, PCB, and exchanger work are licensed. A Noritz with two closed service valves is a handle. A Noritz with an 11 that returns is a service truck.
Frequently Asked Questions
Q: Why is my Noritz tankless water heater not working? A: No 120 V, closed isolation valves, a packed inlet screen, a lockout code (11/12/14/16/61/90), freeze ice, or a mixing valve hiding a hot outlet. Photograph the display before you reset anything.
Q: How do I reset a Noritz that will not heat? A: Photograph the code, fix the obvious cause (gas cock, GFCI, screen, cap), then power off 10–30 seconds or toggle the remote Off/On. One try. A code that returns is licensed. Do not reset a wet cabinet or a unit that smells like gas.
Q: Should I flush a Noritz that will not turn on? A: Not first. Flushing treats scale on a unit that fires (14/16). A dark controller, an 11, or a silent fan needs power, gas, or air — not acid.