Rinnai
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✅ Safe to Use
Rinnai - Error Code 34
Rinnai Water Heater error code 34: Combust air/exhaust thermistor fault.
Is it safe?
✅ Safe temporarily
Safe to use on cold settings temporarily. Heating element failure is a common DIY repair.
Can I fix it?
DIY Possible
Tools: Multimeter, Screwdriver set, Nut driver
Repair cost
DIY: $20–$100 (element or thermistor)
Pro: $100–$300
⏱ 30–60 min
What Does Error Code 34 Mean?
Rinnai Water Heater error code 34: Combust air/exhaust thermistor fault.
Part that typically fails: Heating element / thermal fuse / thermistor
Safe to use on cold settings temporarily. Heating element failure is a common DIY repair.
Symptoms You May Notice
- ⚠️ Water temperature fluctuating
- ⚠️ Unit running constantly
- ⚠️ Error on control panel
Troubleshooting Steps
- 1 Check your owner's manual for model-specific guidance on error code reset procedures
- 2 Test the temperature sensor with a multimeter — replace if reading is outside spec
- 3 Inspect sensor wiring harness for damage or loose connections
- 4 If the error persists after reset and basic checks, contact a qualified technician
🛠️ Tools needed: Multimeter, Screwdriver set, Nut driver
· Time: 30–60 min
⚡ Quick tip: Always try a full power reset first — turn the unit off at the breaker, wait 30 seconds, restore power.
Frequently Asked Questions
What does Rinnai Water Heater error code 34 mean? ▼
Error code 34 on a Rinnai tankless water heater indicates: Combust air/exhaust thermistor fault. The unit has detected this condition and has limited or stopped operation to prevent further damage.
How do I fix Rinnai Water Heater error code 34? ▼
Start by powering the unit off for 30 seconds and restarting. If error 34 returns, the underlying cause (combust air/exhaust thermistor fault) needs to be addressed. Check wiring connections and filters first before replacing components.
Is Rinnai error code 34 serious? ▼
It depends on the root cause. Some 34 errors resolve with a reset. Others indicate a failed component that requires professional repair. Don't continue operating with this error — it can lead to further damage.