Rinnai 32: Water Temperature Sensor Fault

If your hot water has started running noticeably too hot, too cold, or just inconsistent for no obvious reason, and the display shows 32, the likely culprit isn't the burner — it's the sensor that tells the control board how hot the outgoing water actually is.

Applies to: Rinnai tankless and condensing water heaters.

What it means

Outgoing Water Temperature Sensor Fault — the sensor that measures the water leaving the unit has failed or is reading incorrectly, which can cause inconsistent or incorrect hot water temperature. When that sensor reports the wrong value, or nothing at all, the control board is essentially flying blind on the one number it needs to regulate temperature accurately.

Most common causes

A few things can take this sensor out:

• Damaged sensor wiring
• Scale build-up on the sensor
• Failed temperature sensor

What you can safely check yourself

1. No safe homeowner steps beyond noting when the problem started (e.g., after a flush or after very hard water use), which helps a technician diagnose it faster

What the fix costs

Temperature sensors themselves are inexpensive parts, but the labor to open the unit, test resistance values against spec, and confirm the diagnosis makes this mostly a labor-driven repair — expect a bill in the broader $150–$600 diagnostic-and-repair range rather than a large parts cost (Angi, Fixr water heater repair cost guides). It's a relatively minor fix compared to the combustion-related faults on this list, but still one that needs a technician's tools to confirm.

Related codes

• Rinnai 65 — Water Flow Control Fault
• Rinnai LC — Scale Build-Up Warning
• Rinnai 25 — Condensate Trap Error
• Symptom: water not hot enough or runs lukewarm

All Rinnai codes

Every Rinnai water heater fault code — the full list on one page.

Sources

• Rinnai tankless water heater sensor fault reference, service documentation (manufacturer)