Table of Contents
Probably the most common issue when dealing with a furnace that will not stay lit or ignite consistently is a dirty flame sensor. The flame sensor acts as a communication vehicle with the circuit board and tells it when a flame is lit inside the furnace.
What causes a furnace to light then go out?
Another reason why a furnace ignites then turns off could be related to the flame sensor. This key component senses when the flame is on. Often, dust or dirt covers the sensor. If this happens, the sensor won’t detect the flame, and the result is the furnace shuts down.
Why does my furnace turn off after a few seconds?
A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.
Why does my furnace turn on and off every few minutes?
When a furnace starts and shuts off, it could be a sign that you have low airflow. The heat exchanger in the furnace will often overheat if there isn’t enough airflow. The furnace won’t be able to pull fresh air into the blower if the air filters are clogged with dust, pet hair, and other debris.
How do you fix a short cycle on a furnace?
The easiest way to fix a furnace that is short cycling is to remove the flame sensor to clean it. Use a sponge or brush to remove the dirt from the sensor. After the part is clean, follow the manufacturer’s instructions to insert the flame sensor into the furnace.
Can a bad thermostat cause a furnace to short cycle?
A faulty thermostat can be a possible culprit for short cycling. If you’re experiencing a furnace short cycling, the first and easy thing you can do is check your thermostat to see if it’s performing correctly. Many times, a homeowner may forget to switch their thermostat over to the heating mode.
Why does my furnace keep running?
A dirty furnace filter is the number one reason we’ve found that furnaces run constantly. The air filter captures dust, pet hair, and debris that could damage the furnace and keeps it from getting to the heat exchanger. If the filter is dirty, it restricts airflow across the heat exchanger, which causes it to overheat!Nov 24, 2015.
Why is my furnace coming on every 5 minutes?
A dirty filter can cause the furnace to overheat. Short cycle time: 2-5 minutes. If the furnace gets too hot, the switch shuts down the furnace. A dirty filter prevents a flow of fresh, cool air into the furnace to be heated and dispersed.
Why does my furnace turn on every 10 minutes?
Bad Thermostat: If your thermostat has a problem, it can cause your furnace to run cycles that are either too long or too short. If the thermostat is sensing the incorrect temperature and not sending a cut-off signal soon enough, or if the battery is dying, your thermostat can cause your furnace to run erratically.
How do you know a thermostat is bad?
7 Signs You Need to Replace Your Thermostat Your HVAC Keeps Turning On or Off. Faulty Thermostat Readings. Suspiciously High Energy Bills. Constant Temperature Shifts. Thermostat Is Too Old. Thermostat Fails to Respond to Changed Settings. Your HVAC System Short Cycles.
How long should furnace run before shutting off?
Running 10 to 15 minutes per cycle seems acceptable. So is running as long as 20 minutes. Even running every seven or eight minutes may not be a problem, as other factors could lead to more frequent cycling.
How many degrees does a thermostat drop before the furnace kicks on?
For most heating application, the thermostat detects the temperature in a given spot in the house. When it is colder than 74℉, it switches a relay indicating to the furnace to start heating.
What to do if furnace won’t shut off?
Check Your Thermostat If your furnace won’t shut off and you’re worried, don’t panic. The first thing to do is check the thermostat. Check whether your fan is set to On or Auto. If it’s On, try setting it to Auto — this will turn the fan off when the temperature reaches the desired setting.
Why is my furnace running but no heat?
Dirty filters are the most common cause of furnace problems. Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won’t warm up. If the blower is running but no heat is coming out, replace the filter.
How many times should a furnace kick on in an hour?
On average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don’t assume it’s short cycling just yet.
How do I test my furnace thermostat?
How to Test Your Furnace Thermostat Step 1: Reset the thermostat lower or higher. Step 2: Make sure the thermostat is ON. Step 3: Check the wiring. Step 4: Turn breaker back on. Step 5: Reexamine wires. Step 6: Wrap wires together.
How do you tell if you need a new thermostat in your house?
Signs You Need a New Thermostat Heating or cooling system will not turn off or on. The temperature reading is incorrect. Recent spike in your energy bill. Frequent temperature fluctuations. Thermostat is 10 years old or older.
Is it OK to run the fan on the furnace?
As previously mentioned, newer models of furnace systems include fans that are designed to run continuously. Assuming that your heating equipment was properly installed by a professional and has correctly-sized ductwork, letting the fan run continuously may actually help extend its service life.
