Rinnai Error Code 34: Combustion air thermistor (Non-SENSEI) / Lime detecting thermistor (RX/CX) (Tankless)
Rinnai error code 34 on a tankless water heater means: Combustion air thermistor (Non-SENSEI) / Lime detecting thermistor (RX/CX). It is also called Rinnai diagnostic code 34.
Homeowner? What Rinnai code 34 means for you
Check, then call Your tankless water heater is reporting: Combustion air thermistor (Non-SENSEI) / Lime detecting thermistor (RX/CX). This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.
Safe things you can check yourself
- Check that gas reaches the house: other gas appliances work, or the propane tank is not empty.
- Make sure the heater is plugged in and its breaker is on. In winter, keep the power on: it protects the unit from freezing.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the hot and cold water valves under the heater are fully open.
- If you have a remote controller, turn it off and on once. If the code comes back, call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Rinnai error code 34 mean?
On Non-SENSEI units, the combustion air temperature thermistor reports a fault or abnormal combustion conditions; on SENSEI RX/CX units, the lime detecting thermistor on the hot water pipe is faulty.
Applies to: Non-SENSEI Series; SENSEI RX/CX Series
Common causes of Rinnai code 34
- Loose, broken or damaged thermistor harness
- Thermistor resistance out of spec or failed thermistor
- Wrong gas type or improper gas conversion (Non-SENSEI)
A technician checks these and 4 other possible causes on site before replacing any part.
Rinnai models that use code 34
Show all 69 models
C199eC199iCX160iCX199iCXP160iCXP199iR50LSiR63LSe2R75LSeR75LSiR94LSeR94LSiR98LSeR98LSe-ASMER98LSiR98LSi-ASMERC80eRC80iRC98eRC98iRE140eRE140iRE160eRE160iRE180eRE180iRE199eRE199iREP160eREP160iREP199eREP199iRH180RL75eRL75e(A)RL75iRL75i(A)RL94eRL94iRLX94iRU80eRU80iRU90eRU98eRU98iRUC80iRUC90iRUC98iRUCS65iRUCS75iRUR98eRUR98iRUS65eRUS75eRX130iRX160iRX180iRX199iRXP160iRXP199iV53DeV53eV65eV65iV75eV75iV94eV94iV94Xi
Other Rinnai Tankless codes
All Rinnai Tankless Water Heater error codes →
Rinnai code 34: homeowner questions
What does Rinnai code 34 mean?
Combustion air thermistor (Non-SENSEI) / Lime detecting thermistor (RX/CX). On Non-SENSEI units, the combustion air temperature thermistor reports a fault or abnormal combustion conditions; on SENSEI RX/CX units, the lime detecting thermistor on the hot water pipe is faulty.
Is it safe to keep using my tankless water heater with code 34?
It depends on the cause. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.
Can I reset Rinnai code 34 myself?
You can try one reset (power off for 30 seconds, then on). If Rinnai code 34 comes back, the cause is still there and a licensed technician should check it.
Who can fix Rinnai code 34 near me?
Aurora Star Tech Inc. repairs Rinnai tankless water heaters in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Tankless Water Heater No Hot Water: What to Check
Troubleshooting guides
- No hot water All brands · Tankless Water Heater
- Water temperature fluctuates All brands · Tankless Water Heater
Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.39–40. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.