Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater 34 Error Fix: Combustion Air Temperature Sensor Failure

Error code 34 on the Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater means: Combustion Air Temperature Sensor Failure. The sensor that monitors the incoming combustion air temperature has failed. This sensor allows the unit to adjust combustion parameters based on air density — colder air is denser and requires different gas-to-air ratios. While this sensor failure may not prevent operation on some firmware versions, it can cause suboptimal combustion and should be replaced. Check the sensor wiring connection first, then test and replace the sensor if necessary.

The most successful fix is "Test and Replace Combustion Air Temperature Sensor" (medium difficulty, ~45 minutes). Estimated DIY cost: $15-$25. HomeMD has 2 community-ranked fixes for this error.

This error is rated warning severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Test and Replace Combustion Air Temperature Sensor") is rated medium difficulty and takes about 45 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Needle-nose pliers.

DIY cost: $15-$25. Professional repair typically costs $150-$220. Many homeowners save money by trying the top-ranked community fix first.

The Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater has 8 other known error codes, including: 05 (False Flame Detection), 10 (Abnormal Combustion — Blocked Vent), 11 (Ignition Failure — No Flame Detected), 12 (Flame Failure — Flame Lost During Operation), 14 (Thermal Fuse Activated — Overheat Safety), and 3 more.