Rinnai Error Code 33: Heat Exchanger Thermistor
Warning: Your Rinnai water heater is locked out due to a potential heat exchanger issue. It's safe to troubleshoot, but don't attempt to fix it yourself.
How to Fix Rinnai Code 33
- Check if your water heater is receiving power. The display should light up when you turn on the power switch.
- Try resetting the water heater by turning off the power at the circuit breaker, waiting 30 seconds, then turning it back on.
- If the error persists, do not attempt to fix it yourself. Call a professional HVAC technician.
How to Reset Rinnai Code 33
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- Turn the unit back on. If the error returns, the underlying issue needs repair.
What does 33 mean?
Error code 33 on your Rinnai water heater indicates a problem with the heat exchanger thermistor. This sensor monitors the temperature of the heat exchanger and helps regulate the water temperature. If it's not working properly, your water heater may not heat water or could shut down to prevent overheating. This is a yellow hazard level because it's safe to troubleshoot, but you should call a professional for repairs.
Affected Models
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Heat Exchanger Thermistor | RIN-102565600 | — |
| Wiring Harness | RIN-102565700 | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 02 | Stagnant Water Detection | Warning |
| 10 | Air Supply/Exhaust Blockage | Warning |
| 11 | No Ignition | Warning |
| 12 | Flame Failure | Warning |
| 14 | Thermal Fuse | Warning |
| 16 | Over-Temperature | Warning |
| 19 | Electrical Grounding | Warning |
| 25 | Condensate Overflow | Warning |
| 29 | Condensate Neutralizer | Warning |
| 31 | Inlet Thermistor Failure | Warning |