The basic steps to relight a wall heater pilot

To light a pilot light on a wall heater, you turn the control knob to the "Pilot" position, press and hold it down, and hold a lit match or lighter to the pilot burner opening until the flame catches. Once it does, keep holding the knob for 30 to 60 seconds so the thermocouple (a heat-sensing device) warms up and signals the gas valve to stay open. Then turn the knob to "On" and listen for the main burner to ignite.

The whole process usually takes less than five minutes. If the pilot won't stay lit after you release the knob, the thermocouple may be dirty or failing—that is the point to stop and call a technician, because it is a safety device that prevents gas from flowing if there is no flame.

Key Takeaways

  • The control knob must be turned to "Pilot" before you attempt to light anything, and you must press and hold it while lighting.
  • You need a match or lighter that can reach into the pilot opening—a long lighter works better than a short match.
  • After the pilot flame appears, hold the knob down for 30 to 60 seconds to let the thermocouple warm up.
  • If the pilot light goes out as soon as you release the knob, the thermocouple is likely faulty and needs professional replacement.
  • If you smell gas at any point and the pilot will not light, turn off the gas at the wall valve and call a technician.

Locate the pilot light opening and control knob

Open the access panel or cover on the front of your wall heater. You will see a small metal tube or opening—this is the pilot burner. Near it is a control knob with three positions: "Off," "Pilot," and "On." Some heaters label it differently ("Ignition" instead of "Pilot," for example), but the principle is the same.

Before you do anything, make sure the knob is already in the "Off" position and leave it there for at least five minutes. This lets any stray gas clear out of the line. Then turn it to "Pilot."

Light the pilot with a match or lighter

A long-reach lighter (the kind designed for candles or grills) works best because it lets you keep your hand away from the heater. A long match also works. Do not use a short lighter or short match—you will burn your fingers.

While holding the control knob pressed down firmly, bring the flame to the pilot opening. You should see a small blue flame appear within a few seconds. If nothing happens after 10 seconds, pull the lighter away, wait 30 seconds, and try again. Repeat up to three times. If the pilot still will not light, stop—do not keep trying, as gas may be building up.

Hold the knob down to warm the thermocouple

Once the pilot flame is burning, keep pressing the control knob down for 30 to 60 seconds. During this time, the thermocouple—a small metal rod in the pilot flame—heats up and sends a signal to the gas valve that says "there is a flame, keep the gas flowing." If you release the knob too soon, the valve closes and the pilot goes out.

You will feel the knob resist slightly as you hold it; that is normal. After 30 to 60 seconds, slowly release it. The pilot flame should stay lit. If it goes out when ready, wait five minutes and try again. If it goes out a second time, the thermocouple is not working properly and you will need a technician to replace it.

Turn the knob to "On" and check the main burner

Once the pilot is holding steady, turn the control knob all the way to "On." You should hear a soft click or hiss as the main gas valve opens, and the main burner should ignite within a few seconds. The flame should be blue with perhaps a small yellow tip at the very end—that is normal.

If the main burner does not light within 10 seconds, turn the knob back to "Off," wait five minutes, and try the whole process again from the beginning. If it still will not light after a second attempt, call a technician. Do not keep trying repeatedly, as this wastes gas and can be unsafe.

What to do if the pilot light will not stay lit

A pilot that lights but goes out as soon as you release the knob almost always means the thermocouple is faulty. The thermocouple is a safety device—it is supposed to shut off the gas if the pilot flame ever goes out (for example, if a draft blows it out). A broken thermocouple cannot sense the heat, so it tells the valve to close when ready.

Thermocouples can sometimes be cleaned if they are just dusty. If you are comfortable doing so, you can gently wipe the tip of the thermocouple (the part that sits in the pilot flame) with a dry cloth or very fine sandpaper. Then try lighting the pilot again. If it still will not hold, the thermocouple needs to be replaced by a technician—this is not a repair you should attempt yourself, because it involves the gas line.

When to call a professional instead

Stop and call a technician if you smell gas and the pilot will not light. Turn off the gas at the wall valve (turn the handle perpendicular to the pipe) and do not try again. Gas smell means there is a leak somewhere in the system.

Also call a technician if the pilot lights but the main burner will not ignite even after you turn the knob to "On." This usually means the thermocouple is working (because the pilot stays lit), but the main gas valve is stuck or faulty. You should not force the knob or try to disassemble anything—a technician has the tools and knowledge to fix this safely.

If you have tried lighting the pilot three times and it will not catch at all, stop trying. The problem could be a clogged pilot opening, a broken igniter, or a gas line issue. All of these require professional diagnosis and repair.

Frequently Asked Questions

How long should I hold the knob down after the pilot lights?

Hold it for 30 to 60 seconds. This gives the thermocouple time to heat up and signal the gas valve to stay open. If you release it too soon, the pilot will go out. If you hold it much longer than 60 seconds, you are not gaining anything—the thermocouple is already warm enough.

What if I smell gas but the pilot won't light?

Turn off the gas at the wall valve when ready (the handle should be perpendicular to the pipe). Do not try to light it again. Gas smell means there is a leak, and you need a technician to find and fix it before the heater is safe to use.

Can I use a regular lighter instead of a long-reach lighter?

You can, but a long-reach lighter is safer because it keeps your hand farther from the heater. A regular lighter works if you are careful, but you risk burning your fingers. A long match is also a good option.

Why does the pilot light go out right after I release the knob?

The thermocouple is not warming up enough to signal the gas valve to stay open. This usually means the thermocouple is dirty or faulty. Try gently cleaning the tip of the thermocouple with a dry cloth, then light the pilot again. If it still goes out, the thermocouple needs professional replacement.

How often do I need to relight the pilot?

A pilot light should stay lit continuously once you light it. If it goes out regularly, something is wrong—either the thermocouple is failing, there is a draft blowing it out, or the gas pressure is too low. Call a technician to diagnose the problem.