AO Smith Igniter Not Working

The Short Answer: An AO Smith ProLine or ProMax that will not light is usually a hot-surface igniter that never glows, a control in lockout, or no 120 volts to the valve — not a rotten tank. Count the green LED. One trial through the view port. Spark or glow with no flame is gas, not the igniter. Smell gas, leave.

Search Intent & The Real Problem

The tank is cold. You expected a standing pilot and a red piezo. Most current AO Smith gas tanks (ProLine, ProMax, Signature, State / American twins) use an electronic control and a hot-surface igniter that glows orange, then the gas valve opens. Some spark. Some older units still have a piezo pilot. Totally cold with no ignition attempt is this page. LED-only complaints: blinking green. Builder-brand cousin: State Select igniter. Control-brand path: Honeywell no spark. Generic dark burner: burner not lighting.

Polaris is a different machine — submerged burner, not this atmospheric FVIR tray — Polaris problems.

What other guides get wrong

They sell a $12 thermocouple for a tank that has none. They treat a piezo click as a DSI board. They tell you to sand a 120-volt HSI with the gas on. And they skip the LED: six flashes on many AO Smith / State stickers is the igniter circuit. Guessing “bad gas valve” from an Amazon title is how you buy a $250 control for a cracked glow bar.

Step-by-Step Troubleshooting

Step 1: Prove which igniter you have

• What to look for: Jacket card. Rating plate G vs E (E is electric — no igniter). Phone photo of the gas-control sticker.
• Required tools: Flashlight.

Step 2: Count the LED before you blame the ceramic

• What to look for: On many AO Smith / State / American electronic controls (verify your door sticker): 1 flash = normal; 4 = TCO/ECO open; 6 = igniter / HSI circuit; 7 = gas-valve or FVIR; 8 = internal. One slow green blink with a hot tank is not an igniter fault — blinking green.
• Required tools: Watch, phone photo of the LED before you kill power.

No 120 V at the outlet or a tripped TCO will fake a dead igniter. Power-vent units also need the blower to prove — a dead blower is blower not working; do not fire the burner without it (CO). After a storm start at dead after a power outage, not a new glow bar.

Step 3: One look through the port — glow, spark, or dark

• What to look for: Cover on. One heat call (or follow the lighting card). HSI: orange glow for several seconds, then gas, then flame. No glow = open HSI, unplugged harness, control not sending 120 V. Glow, no flame = cock closed, empty LP, valve, or air after a relight. Brief flame, then lockout = flame sense, not the igniter. A bang is delayed ignition — shut it down — loud bang.
• Required tools: Ears and eyes. One trial. Do not pull the FVIR burner door to “see better” if you cannot reseal it.

HSI bars crack. A gray hairline through the silicon nitride is a failed part. Do not ohm it live. A licensed tech will prove 120 V at the connector with the sequence, then replace the bar — not the whole valve — if voltage is there.

Spark-test with the appliance cock off if you only need to see whether the electrode jumps. Then leave the cock off until a licensed tech is there if it never lit. Smell after a click: leave.

Step 4: Gas path without opening the pipe

• What to look for: Appliance shutoff parallel to the pipe. Other gas appliances lighting. LP bottles not empty; a frosted first-stage regulator on a 20°F morning will starve the trial. 1/2” flex on a power-vent ProLine is less of a starvation story than a 199k tankless, but a closed cock is still a closed cock. No gas at other appliances: not getting gas.
• Required tools: Eyes. No fittings wrenches.

Manifold pressure is licensed (NG often ~3.5–7 in. w.c. / LP ~10–11 in. w.c. — confirm the rating plate). Spark or glow with no flame is not a second igniter.

Step 5: FVIR, ECO, and one reset — then stop

• What to look for: Lint-packed flame-arrestor screen under the tank (dryer in the same closet) that soots the chamber and kills sense. TCO/ECO 4-flash after rollout or overheat — never jumper. Water in the combustion chamber or a rust ring at the burner: the tank is dead; shut gas — dripping on the burner. One power cycle after the obvious cause — Honeywell reset. Same lockout on the next call is the end of DIY.
• Required tools: Flashlight at the base, gas off. No paperclip in the control.

A 7-flash after painting or a mower in the closet will never spark no matter what electrode you buy — chamber sensor. Resetting that into vapors is how you get a bang.

When DIY Ends: Calling a Licensed Pro

Stop at gas odor, delayed-ignition bangs, an FVIR door you would have to pull, a melted harness, a 4-flash TCO, a 7-flash vapor lockout, a silent power-vent, and any gas-valve work. You may photograph the LED, confirm the shutoff, and watch one glow/spark trial through the port. HSI replacement inside an FVIR chamber, manometer work, and control swaps are licensed. A cracked glow bar is a parts job. Ten retries is how you glaze the next one and flood the closet.

Frequently Asked Questions

Q: Why is my AO Smith igniter not working? A: Open or cracked hot-surface igniter, no 120 V to the control, a lockout LED (often 6-flash on the AO Smith / State sticker), or a standing-pilot piezo that never sparks. Glow/spark with no flame is gas, not the igniter.

Q: Can I replace an AO Smith hot-surface igniter myself? A: The bar is a part, but it lives in an FVIR combustion chamber. If you cannot reseal that door, hire a licensed plumber. Do not jumper it. Do not keep cycling a dark burner.

Q: The igniter glows but the burner never lights. Is the igniter bad? A: No. Glow proved the igniter. Confirm the shutoff and stop — that is gas, the valve, or a licensed purge after a relight. Do not crack the union.