A.O. Smith Error Code LOC: Controls Locked

Severity
Warning
Type
digital display
Estimated repair cost: $300 — $650 (parts + labor)
Warning: The water heater controls are locked, preventing normal operation. This usually requires a service call to unlock and diagnose the cause.

How to Fix A.O. Smith Code LOC

  1. Step 1: Check the owner's manual for specific instructions on how to unlock the control panel. Some models have a button combination or a sequence of presses to unlock.
  2. Step 2: Try cycling power to the water heater by turning off the breaker for a few minutes, then turning it back on. This may reset the control board and clear the lock.
  3. Step 3: If the above steps don't work, contact a qualified HVAC technician to diagnose and unlock the control panel. Do not attempt to disassemble or repair the unit yourself.

How to Reset A.O. Smith Code LOC

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does A.O. Smith Error Code LOC Mean?

The 'LOC' error code on your A.O. Smith water heater indicates that the control panel has been locked. This feature is designed to prevent unauthorized changes to the water heater's settings. When locked, the unit will typically not respond to button presses or temperature adjustments, effectively disabling its normal functionality. This lockout can occur for several reasons, including accidental activation of the lock feature, a software glitch, or as a safety measure triggered by an underlying issue within the water heater. Because the unit is locked, you won't be able to adjust the temperature or access diagnostic information until it's unlocked. This usually requires specific knowledge of A.O. Smith control systems.

Common Causes

  • Accidental activation of the control lock feature.
  • Software glitch or error within the control board.
  • Low voltage or power surge causing the control board to lock up.
  • Internal fault detected by the control system as a safety measure.

Diagnostic Steps

If... Check Expected
Unit displays 'LOC' and is unresponsive to button presses Check the voltage at the control board. Use a multimeter to measure the incoming voltage. 120VAC or 24VAC (depending on model) within +/- 10%
Voltage is within range Inspect the control board for any signs of physical damage, such as burnt components or corrosion. Control board appears to be in good condition with no visible damage.
Control board appears normal Attempt to unlock the control panel using the manufacturer's specified procedure (refer to service manual). Control panel unlocks and responds to user input.

Applicable A.O. Smith Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
Control Board — — —
Keypad/Button Assembly — — —
Wiring Harness — — —

Related Codes on Same Models

Other codes that affect the same A.O. Smith model families as LOC.

Code Description Severity
E06 Flammable Vapor Detection Critical
E1 Thermistor Failure Warning
E2 Dry Fire Protection Warning
E3 Sensor Fault Warning
E4 High Temperature Cutoff Critical
E5 Communication Error Warning
ECO Emergency Cutoff Critical
LWR Lower Element Fault Warning
UPR Upper Element Fault Warning