Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater 2 FLASH Error Fix: Thermopile Voltage Low

Error code 2 FLASH on the Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater means: Thermopile Voltage Low. The thermopile is not generating sufficient millivoltage to keep the gas control valve open. The thermopile is a sensor made of multiple thermocouples that generates electrical power from the heat of the pilot flame — this power holds open the gas valve electromagnet. Causes: a weak or flickering pilot flame (clean the pilot orifice with compressed air or a fine wire, and clean the pilot tube), a dirty or corroded thermopile connection (disconnect the thermopile connector from the gas control valve and clean the contact surfaces), or a failing thermopile (measure output voltage with a multimeter — it should produce at least 400 millivolts under load when connected to the gas valve, or 750+ millivolts open circuit). If below these values after cleaning, replace the thermopile. Also check for drafts near the water heater that could disturb the pilot flame.

The most successful fix is "Test and Replace the Thermopile Sensor" (medium difficulty, ~40 minutes). Estimated DIY cost: $5-$20. 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 the Thermopile Sensor") is rated medium difficulty and takes about 40 minutes. Tools needed: Phillips screwdriver, Multimeter, Needle-nose pliers.

DIY cost: $5-$20. Professional repair typically costs $110-$160. Many homeowners save money by trying the top-ranked community fix first.

The Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater has 8 other known error codes, including: 1 BLINK / 3 SEC (Normal Operation), 4 FLASH (Temperature Exceeded High Limit), 5 FLASH (Temperature Sensor Failure), 7 FLASH (Gas Control Valve Electronics Failure), 8 FLASH (Insufficient Thermopile Power), and 3 more.

Error code 2 FLASH also appears on 2 other Rheem models: Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace, Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.