A.O. Smith Water Heater Error Code 510

Code 510 indicates a fault in the driving circuit for the main gas valve. This means the control board has detected that the electrical circuit responsible for opening and closing the gas valve is not operating correctly. It can be caused by a failed valve solenoid, damaged wiring, or a faulty control board output stage. Because this fault can potentially result in the burner continuing to fire when it should be off, it requires immediate attention from a qualified technician.

A simple reset is unlikely to permanently resolve code 510 because it points to a hardware fault in the gas valve driving circuit. Even if the unit restarts after a reset, the underlying problem with the solenoid, wiring, or control board remains. Given the potential for an unsafe valve condition associated with this code, the root cause must be diagnosed and repaired before returning the unit to service.

Repair costs depend on the root cause identified during diagnosis. A wiring repair or connector replacement is typically the least expensive outcome, often in the range of $75 to $200 including labor. Replacing the main gas valve generally costs between $150 and $400 depending on the model and parts availability. If the control board is the source of the fault, board replacement can range from $200 to $500 or more. A service call fee will usually apply in addition to parts and labor costs.

Yes, this error carries a significant safety risk. If the driving circuit fault causes the gas valve to remain open, the burner can continue burning even after no hot water is being called for. If you observe flames through the sight glass when the unit should be off, shut off the gas supply and electrical power to the heater immediately and do not restart it until a qualified technician has inspected it.

Basic checks such as inspecting the wiring harness for visible damage or loose connectors can be performed by a knowledgeable DIYer. However, because this fault involves the gas valve and carries a risk of uncontrolled burner operation, full diagnosis and any component replacement should be handled by a licensed plumber or certified appliance technician. A.O. Smith specifically directs that if flames are visible when they should not be, you must contact their Technical Service Department rather than attempting self-repair.