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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
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: