Tankless water heater attempts to start but shuts down with E1; no hot water is produced.

Safety first: Turn OFF power and close the gas shutoff valve. Allow the heater to cool. Do not work near open flame or sparks.

• Step 1 – Verify gas supply: Ensure the manual gas shutoff valve to the Ruud heater is fully open. Confirm other gas appliances in the home operate normally. If not, contact your gas supplier.
• Step 2 – Check venting and air intake: Inspect intake and exhaust terminations for obstructions (leaves, nests, snow, debris). Clear any blockage and reset the unit.
• Step 3 – Inspect igniter and flame rod: Remove the front cover. Locate the igniter/flame rod assembly at the burner. Check for cracks, heavy carbon buildup, or loose wiring. Gently clean the electrodes with fine emery cloth and ensure the ceramic insulator is intact. Re-seat the wiring connectors.
• Step 4 – Check burner area: Look for excessive dust, lint, or rust flakes on the burner surface. Carefully vacuum with a soft brush attachment without damaging burner ports.
• Step 5 – Test again: Restore gas and power, then call for hot water. If E1 returns, the igniter or flame rod may be defective.
• Step 6 – Replace ignition assembly: Shut off power and gas again. Remove mounting screws for the igniter/flame rod assembly, disconnect the harness, and install a new OEM Ruud igniter/flame rod assembly. Reassemble and test.

If ignition still fails, a professional should check gas pressure, gas valve operation, and combustion settings.