Water Heater Igniter Not Working

How the igniter works

On most standing-pilot tank heaters, the igniter is a push button next to the gas control. Pressing it snaps a small piezo element that sends a high-voltage pulse up a thin wire to an electrode beside the pilot burner. The spark jumps from the electrode to the pilot hood and lights the gas. No battery, no power cord.

You hold the gas control knob in on PILOT so gas flows, then click. A.O. Smith's procedure is to click the igniter about once per second for up to 90 seconds while holding the knob.

Heaters with electronic ignition are different. Some use a hot surface igniter that comes on when the heater calls for heat and turns off once the burner lights. Tankless heaters use their own electronic ignition, covered below.

Likely causes

1. 1

   Cause 1: The igniter wire is loose or off

   The wire from the button to the electrode can pop off, especially after someone has had the burner out. A.O. Smith's manual says that if you see no spark through the viewport, make sure the igniter wire is firmly inserted into the white connector. Push it on firmly and try again.

2. 2

   Cause 2: You're getting a spark, but no gas

   If there's a spark and no flame, gas isn't reaching the pilot. A.O. Smith says to check that the gas supply valve is on. Also make sure you're holding the knob fully in on PILOT the whole time you click. A pilot tube that's kinked or clogged will starve the pilot too, and A.O. Smith lists that among the reasons a pilot won't light.

3. 3

   Cause 3: The spark is jumping somewhere else

   A cracked ceramic insulator on the electrode, or an electrode that's been bent away from the pilot, can send the spark to the wrong spot. You might hear the click and see a spark, but not where the gas is. Look closely at the electrode with a flashlight, gas off.

4. 4

   Cause 4: The button itself is worn out

   Piezo buttons wear. A tired one clicks but makes a weak spark or none at all. When the wire is on, the electrode looks right, and there's still nothing, the igniter needs replacing.

How to check for a spark

1. Turn the gas control to OFF.
2. Dim the room lights.
3. Look through the viewport while you click the button. A.O. Smith uses exactly this check.
4. A sharp blue-white spark at the pilot means the igniter works and the problem is gas or the pilot.
5. No spark means checking the wire connection, then the electrode, then the button.

How to light the pilot without the igniter

On older heaters with an open burner door, you can light the pilot with a long lighter. A.O. Smith's guidance is to hold the knob in on PILOT and use a long lighter. Remove the access covers, find the pilot (the small burner next to the thermocouple tip), hold the flame to it with the knob pressed, and keep holding the knob after it lights so the thermocouple can warm up. Then put the covers back.

On sealed-combustion heaters you can't reach the pilot with a lighter. The igniter is the only way in, so a dead igniter means a repair. Don't pry open a sealed burner door to get a lighter in; that seal is part of the heater's flammable vapor protection.

Full steps are on how to light a water heater pilot light.

Replacing the igniter

On many heaters the push-button igniter snaps or screws into a bracket next to the gas control, with one wire to the electrode. Swapping the button is quick. On others, the electrode is part of the pilot assembly inside the burner chamber, and on sealed-combustion heaters that means pulling the burner and replacing a gasket.

Buy the igniter listed for your model number, from the rating plate. Then relight and confirm the pilot stays lit. If the pilot lights now but goes out when you let go of the knob, that's a separate problem, and A.O. Smith names a broken thermocouple as one cause. See pilot light won't stay lit.

Electronic ignition and tankless heaters

If your heater uses electronic ignition, there's no button and no hand-lighting option. A.O. Smith's guide says there's no fallback if the electronic ignition system fails, so you'll need a professional. Some electronic controls also lock out after several failed attempts to prevent gas buildup, which can look like a dead igniter.

Tankless heaters usually show an error code when ignition fails. A.O. Smith's guide says ignition failures stop the unit from starting and points to checking the ignition pack. Look up the code in your manual before you buy parts. Rinnai owners can start with our Rinnai error codes guide.

When to call a pro, and the cost

Call a plumber or gas tech if you have a sealed-combustion heater, an electronic ignition, or a spark and gas but still no pilot. HomeGuide puts water heater igniter replacement at $75 to $350. Service call fees of $50 to $200 may apply. If the pilot then won't stay lit, the next suspects are the thermocouple ($100 to $325 in HomeGuide's figures) and the gas control valve ($150 to $550).