Can I fix A.O. Smith code 0 flashes myself?

Start with these safe checks: Make sure the gas supply valve to the heater is on, then relight the pilot exactly as the label on the heater says. Confirm through the viewport that the pilot is lit. The light can take up to 90 seconds of pilot to start blinking. If the pilot won't stay lit, a thermal switch may have tripped, which can mean flammable vapors, poor air supply or draft problems. Stop and call a qualified technician. If you smell gas, leave and call your gas supplier from outside.

When should I call a technician for code 0 flashes?

If the pilot won't stay lit, a thermal switch may have tripped, which can mean flammable vapors, poor air supply or draft problems. Stop and call a qualified technician. If you smell gas, leave and call your gas supplier from outside. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

A.O. Smith Water Heater Error Code 0 flashes / LED off / no flash:…

What 0 flashes means

The status light isn't lit: the control is off or the pilot is out. Each code flashes, pauses 3 seconds and repeats.

Also shown as: LED off, no flash, depending on the model.

Likely causes

Pilot went out
Control knob off
Gas supply off

Safe first checks

Make sure the gas supply valve to the heater is on, then relight the pilot exactly as the label on the heater says.
Confirm through the viewport that the pilot is lit. The light can take up to 90 seconds of pilot to start blinking.

When to stop

If the pilot won't stay lit, a thermal switch may have tripped, which can mean flammable vapors, poor air supply or draft problems. Stop and call a qualified technician. If you smell gas, leave and call your gas supplier from outside.

Checked against: A.O. Smith Residential Standard Gas Water Heater Service Handbook: diagnostic flash codes. Codes can differ by model and year, so confirm with your owner's manual.