If your furnace is not turning on you should first check if the filter is clean. Dirty filters cause insufficient airflow and can prevent the furnace from starting. Other reasons it won’t start can stem from improper thermostat settings, forgetting to turn on the gas line, or faulty pilot light.

Why does my furnace not ignite sometimes?

If your furnace won’t ignite, the source of the issue may be a broken flame sensor. The sensor is responsible for turning off the gas burners to avoid gas buildup. Once this component starts to malfunction, it may stop the burners from igniting altogether.

Why does my furnace work intermittently?





So, if your furnace keeps turning off and on too quickly, your thermostat might be malfunctioning or broken. There are several things that could be causing your thermostat to not work properly. The wiring could be old and need replacing, it might need new batteries, or it could be the location of your thermostat.

What would cause my furnace to not turn on?

If your furnace doesn’t switch on, the circuit breaker could be shut off. Check your circuit breaker panel to make sure all switches for your HVAC system are set to “ON.” Check Your Thermostat. If your furnace isn’t turning on, the thermostat may have lost its programming or reset.

How do you know if your furnace ignitor is bad?

If you have a faulty furnace ignitor, it won’t produce that tiny spark to heat the air coming from your Furnace. Your heater blows air at the same temperature as the cold outside air without it. Cold air blowing through your vents is a good sign that you have a heating problem within the Furnace.

How do I know if my furnace spark ignitor is bad?

Your furnace won’t run: The most obvious sign that your ignitor is bad is that it won’t ignite, and this generally manifests itself in your furnace failing to run when you activate it. One word of caution, though: this can also be caused by other issues, some of which are electrical.

How long should furnace run before shutting off?





If your furnace is operating correctly, it should cycle about 2 to 3 times per hour. How long it operates depends on how cold it is outside. In milder temperatures, it may run for 10 to 15 minutes. The colder it gets, the longer the run cycle will be.

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

You Have a Faulty Ignition Sensor (Pilot Light)

The pilot light or ignition sensor is usually the most common issue when your furnace will not ignite. This is typically the problem if you can hear your furnace click on but it does not fire up.

How much does it cost to replace a furnace ignitor?

Here’s the bottom line: Whether for a natural gas furnace, oil, or a propane furnace, replacing a furnace ignitor–including parts and labor–will cost you around $300 – $425 for a qualified contractor to install. Compare that to, say, a draft inducer motor, which will cost $400 – $1,500 to replace.

Can a furnace ignitor be cleaned?



If your furnace has a spark ignitor and it’s working haphazardly, it too could be covered with soot, and a blast of compressed air may be enough to clean it. Compressed air can also clean a blocked pilot tube that is causing the pilot flame to burn weakly or not at all.

How do you clean the ignition sensor on a furnace?

The Process of Cleaning a Furnace Flame Sensor

  1. Turn off the furnace power.
  2. Turn off the gas valve.
  3. Remove the furnace flame sensor.
  4. Clean the sensor with an emery cloth.
  5. Return the flame sensor.
  6. Restart the furnace.

Where is furnace sensor located?



A furnace flame sensor is a very basic part of your furnace. It’s located on the burner assembly and is just a thin metallic rod. It’s usually bent, and it sits just in front of the pilot flame inside the furnace.

How do you trick a flame sensor?

Luckily, making such a check is very easy:

  1. Take a multimeter with microamps (µA) measuring system.
  2. Keep the furnace system turned on.
  3. Connect it to the wire that is leading to the gas valve.
  4. Connect the other side of the multimeter to the sensor terminal.
  5. Take the lead away from the flame sensor.

How often does a flame sensor need to be cleaned?

The service life of a furnace is 10 to 20 years on average. This means you’ll have to replace a flame sensor once, twice or three times over the course of the furnace’s life. Having a bad flame sensor is completely normal–you just need to know how to properly identify when it’s gone bad so you can replace it on time.

Do flame sensors wear out?

Do flame sensors wear out? Flame sensors wear over time. However, often the problem is a dirty sensor, rather than a broken one. Since these sensors are designed to have a low tolerance for reading variations, they might misread from the slightest carbon coating.

Can a flame sensor be intermittent?



The flame sensor is a safety component that detects whether or not there is a flame in the combustion chamber. If this sensor is dirty, the dirt can cause the sensor to operate intermittently. When this happens, your furnace will most likely light, but because the sensor can’t properly detect if a flame is present.