Takagi Non-Condensing Code 321
Inlet thermistor fault. The sensor reading incoming cold water temperature is not reporting correctly — the reference the unit uses to decide how much heat to add. Shown as 32 on a T-K4 or T-KJr2 remote, or two flashes of the red LED.
Also displayed as: 32
Part replacementThe verdict
Replace a part
An inexpensive sensor with a service call around it. The unit may keep running while the reading is wrong, which shows up as temperature that is off rather than absent.
Typical cost: $150–$450
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 Non-Condensing — not averaged across the brand.
Source: Takagi Non-Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 12), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note when the unit was last flushed and whether your water is hard.
- Book a service call.
Frequently asked questions
Two flashes covers both thermistor codes.
It does — 311 and 321 both flash twice. If you have no remote, the flash count tells you it is a thermistor and a technician's meter tells you which one.
Code 321 on other Takagi series
Other Takagi series report code 321 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
2 other Takagi Non-Condensing codes point at a thermistor too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: