Why is my furnace pilot light not lighting?

Author: Dr. Godfrey Conroy I  |  Last update: Thursday, October 23, 2025

One of the most common reasons a furnace is not lighting is when your gas line is blocked or clogged. The line in which the furnace draws its fuel can be either blocked or too small for the furnace.

What to do when the pilot light won't ignite?

turn off the power, take a dish cloth or scrubby pad and clean the thermocouple, itll be located where the pilot flame is. then return power and see if it fires up.

Why is my furnace turning on but not igniting?

Defective Igniter or Pilot Light

If it clicks but your furnace won't ignite after the combustion cycle, the electronic ignition systems probably need to be replaced. In cases where the furnace ignition starts normally but only stays on for a few minutes and then goes out, a new pilot light likely needs to be installed.

How do I reset my furnace ignitor?

You can reset the ignition on your furnace simply. To do this you must cut the power to the furnace first by turning off the circuit that powers it. Once the power is off you can remove the burner door to reveal the ignitor. Turn this to “off” and leave it off for at least 5 minutes.

Why is my gas furnace pilot not lighting?

If no gas is flowing to the pilot light, you obviously won't be able to get it to light. This can happen because the furnace's main gas valve isn't fully open or if your gas supply is shut off or interrupted. There is also a chance that the pilot tube that supplies gas to the flame is clogged.

How To Light A Furnace Pilot Light (DIY! Save $$ and Time)

Can I relight the pilot light by myself?

The Short Answer Is: It is generally safe for a homeowner to relight a furnace pilot light, as long as they follow proper precautions and guidelines. To do it yourself, first, turn off the furnace's gas supply and wait for a few minutes to allow any lingering gas to dissipate.

How to tell if a furnace ignitor is bad?

The Short Answer Is: Warning signs of a bad furnace ignitor include the furnace not starting or heating, a noticeable clicking sound without ignition, or frequent short cycling where the furnace turns on and off rapidly. Additionally, if the ignitor appears cracked or discolored, it may need replacement.

Can hear your furnace click on but it does not fire up?

Most likely, your furnace is making a clicking noise and not providing heat because your furnace's spark igniter is trying to ignite your pilot light or burners but is failing to do so. In other words, there's an ignition system malfunction that needs to be fixed. Otherwise, your furnace won't start.

How do I get my furnace to ignite?

Relighting Pilot Lights
  1. Turn Off the Power. The first step to safely relight your furnace is to turn off the power to this heating system. ...
  2. Turn Off the Gas. Next, turn off the gas supply to the furnace. ...
  3. Wait for the Gas to Dissipate. ...
  4. Locate the Pilot Light. ...
  5. Relight the Pilot Light. ...
  6. Hold the Reset Button. ...
  7. Turn on the Furnace.

Why is my furnace running but not lighting?

If your furnace has been working without any problems up to now and suddenly will not ignite, there's a good chance that either the electronic ignition system has failed or that the standing pilot lights that comes before the ignition process has gone out.

How do I force my furnace to start?

First, confirm the switch is in the "on" position, and if it is, see if your furnace starts up. If the switch is flipped down in the "Off" position, then your furnace will not turn on. If your heating system still does not start up, it might be due to a blown furnace fuse or tripped circuit breaker.

How much does it cost to replace a furnace ignitor?

Furnace ignitor cost

A furnace ignitor replacement costs $100 to $250 on average. Most universal hot-surface ignitor prices are $15 to $35 for the part alone. Gas furnace ignitor prices are $20 to $100 for parts from the original manufacturer (OEM). The labor cost to replace a heater ignitor is $80 to $200.

Why is my furnace not trying to ignite?

Several factors can stop a furnace from igniting: Thermostat Malfunctions: Incorrect thermostat settings or a faulty thermostat. Fuel Supply Problems: Insufficient propane supply, closed valves, or leaks. Ignition System Failure: Issues with the pilot light, electronic igniter, or other ignition components.

Why won't my pilot light relight?

YOU EITHER NEED A NEW THERMOCOUPLE, OR THE EXISTING THERMOCOUPLE IS NOT IN THE FLAME, OR THE EXISTING THERMOCOUPLE IS ENCRUSTED WITH SOMETHING, OR WHEN YOU ARE TRYING TO RE-LIGHT THE PILOT LIGHT YOU ARE NOT HOLDING THE GAS BUTTON IN FOR A LONG ENOUGH TIME.

Why is my pilot light not kicking in?

The issue could be: A dirty tube: If the pilot light tube is dirty, it can put out the light over time. You'll need to clean it with something abrasive to get it working again. Not enough gas: Sometimes, the gas valve will leak, or something else prevents gas from getting through the line.

Why is my furnace pilot light on but not firing up?

If your gas furnace initiates the start cycle but doesn't fire up, it's likely because of a faulty, damaged, or dirty ignitor/sensor. This is a very common problem — you can try to clean the sensor and replace the ignitor.

Why is my furnace making a sound but not turning on?

Check the pilot ignition light.

(Electronic ignitions will not have a pilot light.) If your furnace clicks on or initiates the start cycle, but does not fire up, you likely have a faulty or dirty ignitor/sensor. This is one of the most common furnace problems.

Is it hard to replace a furnace ignitor?

In short, yes, you can DIY a hot-surface ignitor replacement. It shouldn't be too difficult if you have experience fixing things around the house. However, if you typically feel clueless about troubleshooting household appliances, this may not be the right job for you.

How to know if a flame sensor is bad?

Top 7 Signs of a Bad Furnace Flame Sensor
  1. Flue Line Corrosion. The flue line is responsible for venting harmful gases from the furnace outdoors so nothing seeps into the house. ...
  2. High Energy Bills. ...
  3. Yellow Flames. ...
  4. Furnace Short Cycling. ...
  5. Dirt on the Sensor. ...
  6. Visible Damage on the Flame Sensor. ...
  7. Age.

Why is my heater clicking but not turning on?

The first thing to check is your thermostat. It might be clicking yet failing to trigger the heating. Ensure it's set to 'heat' mode and the temperature is above the current room temperature. Incorrect settings or a malfunctioning thermostat can be a primary reason for the furnace clicking but not turning on.

What happens if the pilot light won't light?

In many cases, the reason that you can't get your pilot light to ignite is that the pilot tube is clogged. This is a small metal tube that supplies the gas needed to ignite the pilot and keep it lit. The pilot tube often becomes clogged with debris, and this will prevent gas from flowing to the pilot light.

Where is the reset button on a furnace?

In most newer systems, the button is often directly next to the blower motor, while in older systems, it may be harder to spot as it is sometimes underneath or behind the motor. The reset button is often made of yellow or red plastic and marked with a large “R ” to make it easier to spot.

How much does it cost to relight a pilot?

Additionally, a pilot light can blow out over time. A plumber can help reignite the pilot light. They will charge you an hourly fee of $40 to $150. This is usually a fairly brief project, and may just take an hour.

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