Rinnai Error Code 33: Heat exchanger thermistor fault (Tankless)
Rinnai error code 33 on a tankless water heater means: Heat exchanger thermistor fault. It is also called Rinnai diagnostic code 33.
Homeowner? What Rinnai code 33 means for you
Check, then call Your tankless water heater is reporting: Heat exchanger thermistor fault. 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 33 mean?
The heat exchanger temperature thermistor or its circuit is reading abnormally.
Applies to: SENSEI Series; SENSEI RX/CX Series; Non-SENSEI Series
Common causes of Rinnai code 33
- Loose, broken or damaged thermistor harness
- Scale build-up on the thermistor
- Thermistor resistance out of spec
A technician checks these and 1 other possible causes on site before replacing any part.
Rinnai models that use code 33
Show all 89 models
C199eC199iCU160eCU160iCU199eCU199iCX160iCX199iCXP160iCXP199iR50LSiR63LSe2R75LSeR75LSiR94LSeR94LSiR98LSeR98LSe-ASMER98LSiR98LSi-ASMERC80eRC80iRC98eRC98iRE140eRE140iRE160eRE160iRE180eRE180iRE199eRE199iREP160eREP160iREP199eREP199iRH180RL75eRL75e(A)RL75iRL75i(A)RL94eRL94iRLX94iRSC160eRSC160iRSC199eRSC199iRU80eRU80iRU90eRU98eRU98iRU130eRU130iRU160eRU160iRU180eRU180iRU199eRU199iRUC80iRUC90iRUC98iRUCS65iRUCS75iRUR98eRUR98iRUR160eRUR160iRUR199eRUR199iRUS65eRUS75eRX130iRX160iRX180iRX199iRXP160iRXP199iV53DeV53eV65eV65iV75eV75iV94eV94iV94Xi
Other Rinnai Tankless codes
All Rinnai Tankless Water Heater error codes →
Rinnai code 33: homeowner questions
What does Rinnai code 33 mean?
Heat exchanger thermistor fault. The heat exchanger temperature thermistor or its circuit is reading abnormally.
Is it safe to keep using my tankless water heater with code 33?
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 33 myself?
You can try one reset (power off for 30 seconds, then on). If Rinnai code 33 comes back, the cause is still there and a licensed technician should check it.
Who can fix Rinnai code 33 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.38. 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.