Rinnai SENSEI RX Code 32
Outgoing water temperature thermistor fault. The sensor that reads the temperature of the water leaving the heater is out of range or not reporting. Rinnai's checks are the wiring back to the PC board, then scale build-up on the thermistor itself, then its resistance against a published table — around 11.4-14K ohms at 59°F, falling to 2.2-2.7K ohms at 140°F.
Part replacementThe verdict
Replace a part
This is a sensor, not a combustion fault, and it is one of the cheaper repairs on the unit. Rinnai's step before condemning it is to remove it and clean off scale — so on hard water a flush plus a clean can be the whole fix. The job needs the water isolated and the unit drained, so it is a plumber's call-out rather than a DIY afternoon.
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 SENSEI RX — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 37), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note whether your water is hard and when the unit was last flushed — Rinnai's own step is to check the thermistor for scale build-up before replacing it.
- Book a service call; the water has to be isolated and the unit drained to reach the sensor.
Frequently asked questions
Will descaling clear code 32?
It can, when the cause is scale on the sensor — that is Rinnai's step 2 before any replacement. It will not help if the thermistor has genuinely failed, which the resistance check settles.
Is the part expensive?
The thermistor itself is one of the cheapest components in the unit. Most of the cost is the visit and the drain-down.