A.O. Smith Water Heater Error Code 8

Error code 8 on an A.O. Smith water heater means the control board has detected an open circuit in the hot surface ignitor system. This tells the unit that the electrical path to the ignitor is broken, either because the ignitor itself has failed or because of a wiring problem. The heater will not attempt to light the burner while this fault is active.

Error code 8 is not an active safety hazard because the unit is preventing ignition rather than allowing an unsafe condition. The heater has shut itself down as intended. However, you should not attempt to bypass the lockout or manually ignite the burner, as the ignition control system exists to prevent unburned gas from accumulating.

If the repair only involves reseating a loose connector, there may be no parts cost at all, just the cost of a service call if you hire a technician. Replacing a failed hot surface ignitor typically costs between $20 and $80 for the part, with labor adding $75 to $200 depending on your area and service provider. A control board replacement, if needed, can range from $100 to $300 or more for the part alone.

Start by inspecting all wiring and connectors leading to the hot surface ignitor, reseating any loose connections and looking for damaged or corroded terminals. If the wiring checks out, test the ignitor itself with a multimeter for continuity. A reading of infinite resistance confirms the ignitor element is open and the part needs to be replaced. If both the wiring and ignitor test good, the control board output should be evaluated.

A reset may temporarily clear the fault display, but if the underlying open circuit condition still exists, the error will return as soon as the unit attempts to ignite. Resetting is useful for confirming whether a fault is persistent, but it does not repair a broken ignitor or damaged wiring. The root cause must be corrected for the unit to operate normally.