mypros+
Error code reference

A.O. Smith Water Heater Error Code 15

One or both temperature adjustment buttons are stuck.

A.O. Smith codesA.O. Smith water heater codes

One or both temperature adjustment buttons are stuck.

First step from the service manual

Press and release each of the temperature adjustment buttons.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for 15.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What 15 means on a A.O. Smith water heater

Error code 15 on an A.O. Smith water heater indicates that one or both temperature adjustment buttons on the control panel are detected as stuck or continuously pressed. The control board monitors the state of these buttons and triggers this fault when it senses a button input that does not release within the expected timeframe. This prevents the unit from accepting valid user input and can interfere with normal temperature regulation.

The most common cause is physical obstruction or debris around the button mechanism. Mineral deposits, soap residue, or corrosion can accumulate around the button perimeter and prevent the button from springing back to its released position after being pressed. In some cases, the plastic button cap itself may be warped or misaligned, causing it to bind against the panel housing.

A secondary cause is a faulty button switch or control board input circuit. If the tactile switch beneath the button cap has failed internally, it may register as a continuous press even when no physical obstruction is present. This type of failure typically requires replacing either the button assembly or the full control board, depending on how the components are integrated in the specific unit. The first diagnostic step is to firmly press and release each temperature adjustment button individually to check whether physical manipulation clears the fault.

Source: manufacturer service documentation.

Common causes of 15

  1. 01

    Debris or residue around button

    Wiring / connection

    Mineral buildup, dust, or moisture residue can accumulate around the button perimeter and prevent it from returning to its raised position after being pressed. Inspect the button edges closely for visible buildup or stickiness.

  2. 02

    Button physically binding against housing

    Wiring / connection

    The plastic button cap can warp over time or shift out of alignment, causing it to bind against the surrounding panel housing. Pressing the button at different angles while releasing may reveal this type of binding.

  3. 03

    Failed tactile switch beneath button cap

    Part replacement

    The tactile switch component under the button cap can fail internally and register as a continuous press signal to the control board even when no physical obstruction exists. This typically requires parts to correct.

  4. 04

    Moisture or corrosion on button contacts

    Part replacement

    Water intrusion or condensation near the control panel can cause corrosion on the button contacts or switch terminals, leading the control board to read a persistent button press. Inspect the panel area for signs of moisture damage.

  5. 05

    Control board input circuit fault

    Part replacement

    If the control board's button input circuit has failed, it may incorrectly report a stuck button even when the physical buttons are functioning normally. This is the least common cause and requires control board replacement.

See the test procedure for each cause

Frequently asked questions about 15

What does 15 mean on a A.O. Smith water_heater?
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.
How do I fix error code 15 on my A.O. Smith water heater?
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.
Will resetting my A.O. Smith water heater clear error code 15?
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.
Is error code 15 on an A.O. Smith water heater a safety concern?
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.
How much does it cost to repair error code 15 on an A.O. Smith water heater?
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.

Related A.O. Smith water heater codes

All A.O. Smith water heater codes
View all 36 A.O. Smith water heater codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass