A.O. Smith Water Heater Error Code 15

Error code 15 means the control board has detected that one or both temperature adjustment buttons are stuck in the pressed position. The unit monitors button input states and triggers this fault when a button signal does not release as expected. This can result from physical debris, a binding button cap, a failed switch, or a control board issue.

A simple reset is unlikely to permanently clear error code 15 if the underlying cause is still present. Because the code is triggered by a continuous hardware signal from the stuck button, the control board will re-detect the fault after any reset as long as the button remains stuck or the switch has failed. Resolving the physical or electrical cause of the stuck button is necessary for the code to clear.

If the fault is caused only by debris or a binding button, cleaning may resolve it at no parts cost, with only a service call fee if a technician is involved, typically in the range of $75 to $150. If the tactile switch or button assembly needs replacement, parts and labor costs can range from $100 to $250. A full control board replacement, if required, can range from $200 to $450 or more depending on the model.

Start by pressing and releasing each temperature adjustment button firmly to check for physical sticking. If a button feels sticky or does not spring back cleanly, inspect the button edges for debris or corrosion and clean around the button carefully. If the buttons move freely but the code persists, the issue may be a failed tactile switch or a control board fault, which would require component replacement.

Error code 15 itself is primarily a control input issue rather than a combustion or pressure safety hazard. However, if the stuck button is causing unintended temperature changes, water temperature could rise to an unsafe level. It is advisable to resolve the fault promptly and verify that the set temperature is at a safe setting before returning the unit to regular use.