Tankless water heater displays E6; unit may not modulate correctly and water temperature may be unstable.

Safety first: Turn OFF power and gas. Moving fan blades and live wiring can be hazardous.

• Step 1 – Check venting: Inspect both intake and exhaust terminations for obstructions. Clear any debris, snow, or insect nests.
• Step 2 – Listen for fan operation: Restore power (gas still OFF) and call for hot water. Listen for the fan attempting to start. If it hums or does not spin, turn power OFF again.
• Step 3 – Inspect fan and wiring: Remove the front cover. Locate the combustion blower assembly. Check for loose connectors, damaged wires, or foreign objects preventing the fan from turning. Manually spin the fan wheel gently; it should rotate freely.
• Step 4 – Clean fan wheel: If dust or lint buildup is present, carefully vacuum and wipe the blades without bending them.
• Step 5 – Replace fan assembly: If the fan is seized or does not run when powered, disconnect wiring, remove mounting screws, and install a new OEM Ruud combustion blower assembly. Ensure gaskets are properly seated to prevent flue gas leaks.

After replacement, restore gas and power, then test. If E6 persists, the control board fan driver circuit may be faulty and should be checked by a technician.