Noritz Code 14 means the thermal fuse has blown. This is a one-time safety cutoff that trips when the heat exchanger reaches a dangerously high temperature. The fuse cannot be reset - it must be replaced.
I've been out to fix this code more times than I can count, and it's almost never a one-part repair. Scale buildup acts like a thermal blanket that traps heat inside the exchanger until that fuse has no choice but to blow. Swap the fuse without a proper descaling flush and you're setting up the exact same failure again in three weeks.
Code 14 is basically the nuclear option your Noritz uses when things get dangerously hot inside. Unlike most codes that'll clear with a power cycle, this one means something physically broke inside the unit. Expect a two-part repair: a new fuse harness plus a serious descaling job. Parts alone usually run $20-40, but with labor and a flush you're looking at $150 to $350 total.
Most Likely Causes
Based on aggregated repair data, here is the probability breakdown for this error code:
Scale buildup on heat exchanger reducing water-side heat absorption40%
Chronically low water flow rate causing localized overheating24%
Thermal fuse component failure (rare without another underlying cause)22%
Inaccurate flow sensor reporting false flow to control board14%
Symptoms You May Notice
Error code 14 is locked on the controller display and won't budge no matter how many times you tap reset or cut power and restore it.
Zero hot water. Not lukewarm or inconsistent. The unit won't even try to light. You might hear one faint click from the igniter and then nothing.
If you were paying attention in the weeks before this happened, you probably saw Code 29 flashing on the display a few times, clearing itself, and coming back. That was your warning.
The unit is completely dead. No startup sequence, no burner rumble, no clicking igniter. Just that code sitting there and nothing else happening.
Can you reset a Noritz waterheater to clear the 14 code?
There's no reset sequence for Code 14. None. The thermal fuse is a physical wire that's literally melted apart inside the unit, so the control board will keep seeing an open circuit no matter how many times you unplug it or press buttons. Shut off the gas valve and cold water inlet valve while you wait for a tech. Don't leave gas running to a unit that won't fire.
Follow these steps in order. We start with the easiest external fixes before opening up the machine.
ComponentComponent Under Test
Expected Range0–2 ohms
ConditionIf Open (OL) or infinite, replace component.
Replacement Parts
If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.
Part Name
OEM Number
Estimated Price
Thermal Fuse100169765 · $8–$20
100169765
$8 – $20
Inlet Filter Screen100113571 · $5–$15
100113571
$5 – $15
Frequently Asked Questions
Can I reset Noritz Code 14 myself?
No, and I know that's not what you want to hear. The thermal fuse isn't a switch or a sensor you can shake back to life. It's a physical wire that's literally melted apart inside a ceramic housing. Once it's gone, it's gone. There's no button combo, no reset sequence, no unplugging trick that fixes it. It's like asking if you can reset a blown car fuse by tapping the dashboard. The wire is broken. It has to be replaced with a new OEM part by a qualified tech.
How much does it cost to fix Noritz Code 14?
Budget $150 to $350 for a standard repair. That covers the service call, the new fuse harness (usually around $20-40 for the part itself), and a basic descaling flush. But here's where it can get expensive: if the overheating was bad enough to damage or warp the heat exchanger itself, you might be looking at $600 or more, or a conversation about full unit replacement. I always check the exchanger while I'm in there. If it's discolored or warped, I tell the customer straight up what they're dealing with.
Why did my Noritz Code 14 come back after the fuse was replaced?
Because whoever fixed it only replaced the fuse and didn't deal with the scale. I've literally seen brand new fuses blow in under a week because the heat exchanger was still coated in mineral deposits. The scale traps heat, the water can't pull it away fast enough, temps spike, and the new fuse pops just like the old one did. A proper descaling flush takes about an hour with a circulation pump and food-grade vinegar. If your tech skipped that step, the repair wasn't finished. Call them back.
Is Code 14 the same as Code 29 on a Noritz?
They're related but not the same. Code 29 is the early warning shot. It means the unit detected high heat and shut down before any permanent damage happened. Code 14 means the unit got hot enough that the safety fuse physically melted apart. If you saw Code 29 pop up a few times and just reset it without getting the unit serviced, that's exactly how you end up with a 14. The 29 was your warning. The 14 is the bill.
How can I prevent Code 14 on my Noritz?
Annual descaling flush, every single year. Get food-grade white vinegar, a submersible pump, a five-gallon bucket, and some vinyl tubing, hook it up to the service ports and circulate for about an hour. If your water is really hard, do it every six months. Adding a scale inhibitor filter on the cold water inlet helps a ton too, especially if you live somewhere the water leaves white spots on everything. It's basically an oil change for your tankless heater. Skip it long enough and something expensive breaks.