🔍
Rinnai Water Heater ⛔ Do Not Use

Rinnai Water Heater Error Code 73

Rinnai Water Heater error code 73: Burner sensor abnormal.

Last reviewed: Last updated:

Methodology: We combine OEM HVAC documentation with field repair patterns, then review for safety-first troubleshooting.

Sources: HVAC manufacturer documentation, installation/service manuals, and technician-reported repair patterns.

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

Is it safe?
⛔ No — stop using
Do NOT operate — potential gas or CO hazard. Ventilate the area and call a technician immediately.
Can I fix it?
Technician Required
Repair cost
Pro: $150–$600
⏱ 1–3 hours (pro)

What Does Error Code 73 Mean?

Rinnai Water Heater error code 73: Burner sensor abnormal.

Part that typically fails: Gas valve / igniter / heat exchanger

Do NOT operate — potential gas or CO hazard. Ventilate the area and call a technician immediately.

Symptoms You May Notice

What the Technician Will Do

🔧 Professional repair required. Do not attempt DIY — this repair requires specialized tools or certification.
  1. 1 Check your owner's manual for model-specific guidance on error code reset procedures
  2. 2 Test the temperature sensor with a multimeter — replace if reading is outside spec
  3. 3 Inspect sensor wiring harness for damage or loose connections
  4. 4 If the error persists after reset and basic checks, contact a qualified technician
⚡ 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 73 mean? ▼
Error code 73 on a Rinnai tankless water heater indicates: Burner sensor abnormal. 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 73? ▼
Start by powering the unit off for 30 seconds and restarting. If error 73 returns, the underlying cause (burner sensor abnormal) needs to be addressed. Check wiring connections and filters first before replacing components.
Is Rinnai error code 73 serious? ▼
It depends on the root cause. Some 73 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.

More Rinnai Water Heater Error Codes

All Rinnai water heater codes → All Rinnai HVAC codes →

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