Ruud tankless water heater displays error code 14; unit shuts down and will not provide hot water.

Safety first: Turn OFF power and gas. Allow the unit to cool completely before touching internal parts.

• Step 1 – Check water flow and filters: Ensure all isolation valves are fully open. Remove and clean the cold water inlet filter screen.
• Step 2 – Descale heat exchanger: Connect hoses and a pump to the hot and cold service valves. Circulate descaling solution through the heat exchanger for 45–60 minutes, then flush with clean water.
• Step 3 – Inspect overheat cutoff and thermistor: Remove the front cover. Locate the overheat cutoff fuse and outlet thermistor on the heat exchanger. Check wiring and connectors.
• Step 4 – Replace overheat cutoff or thermistor: If either component tests open or out of spec, replace with OEM Ruud parts. Remove mounting hardware, swap the part, and reconnect wiring.

If the error recurs after descaling and sensor replacement, a technician should evaluate gas input and control board operation.