If dirt or dust covers the sensor, the flame isn't detected, and the furnace shuts down. Sometimes all that is needed is a simple cleaning of the flame sensor, but it may also be worn out and need to be replaced.
Having A Furnace Bad Flame Sensor
A furnace with a bad flame sensor means that the flame will shut off immediately after it ignites. The sensor's job is to monitor the gas valve. It acts as a safety precaution so that raw gas doesn't get into your home. The sensor switches off when it doesn't detect a flame.
If your furnace will not stay on, it is usually a dirty flame sensor. This is one of the routines that every homeowner can do to troubleshoot a energy efficient furnace. By cleaning the flame sensor once a season, you can keep the furnace from cycling on and off too fast. Check out more home improvement tips in our e-
There are multiple reasons why your furnace is short cycling. These could include a dirty filter, blocked vent, or malfunctioning flame sensor. You can switch for a clean furnace filter, or have your HVAC technician resolve a more complicated issue.
Very likely your furnace has a flame sensor. The ignition control turns the main burner gas on for 3-5 seconds after the hot surface ignitor has warmed up. If the flame sensor and ignition control don't detect that the burners have lit, the main burner gas is shut off and a new trial for ignition begins.
Insufficient airflow or insufficient gas pressure. A defective, malfunctioning ignition board, flame sensor, light switch, thermostat, thermocouple, fan limiter, or draft inducer fan. The drainage line is blocked, resulting in a full condensate pan. Temperatures are so low that the furnace cannot stay lit.
Short cycling is a common sign of a bad flame sensor. The sensor thinks that there isn't a flame, so it shuts off the gas as a safety mechanism. Except, there is a flame and without the gas to supply it, it dies. This is a frustrating problem, but an HVAC technician can fix it.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
The flames from the burners may be going out because they're struggling to draw enough oxygen for combustion through excess dirt or other grime along their surface. This is often a problem in a furnace that hasn't received regular maintenance.
To begin, ensure that all the filters of your furnace are clean. Also, get the filters replaced every few months to ease the burden on your HVAC system and ensure that fresh air comes filtered into your home. Another common cause of your furnace turning on and off after a few minutes is a faulty pressure switch.
The top causes to blame when a furnace kicks on and off are: The air filter needs changed. The thermostat batteries need to be replaced. Blower motor malfunctions.
There is a work-around to waiting. If there is no safety risk (like a gas leak), a furnace can be reset to bypass this wait. Turn off the furnace's power switch and wait 10 seconds before turning it back on.
Turn on the heat on the thermostat and increase the temperature. You should hear a sound from both the thermostat and the furnace, and whichever doesn't make a sound has a problem.
Short cycling indicates a problem within a heater that is cutting off its heating cycle before it finishes. This can be caused by a range of issues, which vary in severity and necessary repair.
If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.
If your furnace shuts off after a few minutes and starts more than eight times an hour, it may require repair. Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.
If the sensor is dirty or malfunctioning, it might not sense the flame even if it's present. As a result, the furnace will shut down immediately after kicking on.
Most furnace flame sensors cost less than $20, but if you opt to have a professional HVAC technician make the repair, you can expect to pay between $75 and $250. Need help replacing your flame sensor?