What does a clogged oven filter do

Tips for troubleshooting and repairing high efficiency ovens

  • 01 of 10


    Your highly efficient kiln is a high-tech machine with which you can heat your home comfortably and with low energy consumption. But like any machine, it can stop working at times and when that happens it usually means calling the heating and ventilation repair shop.

    But if your oven isn't firing, there are actually a number of things you can check or fix before calling a service professional. These repairs range from simple to technical. If you are not satisfied with any of the tips below, please contact a service technician, but most are things that the weekend warrior can tackle with ease.

    The following list shows the most common reasons why a high-efficiency oven does not work, in order of likelihood. Details of each item are described on the following pages:

    1. Bad thermostat
    2. The oven switch is off
    3. Clogged oven filter
    4. Faulty high limit switch
    5. Electronic ignition: Faulty hot surface igniter
    6. Electronic ignition: faulty flame sensor
    7. Defective pressure switch
    8. Clogged condensate line to the floor drain
    9. Broken furnace flue pipe
  • 02 of 10

    Bad thermostat

    The thermostat that controls your high efficiency stove is the first place that is checked. Make sure it is working properly and calling for heat. You probably have one digital thermostat, if you have a high efficiency oven.

    Possible problems could be:

    For more information, see the Troubleshooting a Cooker Thermostat guide.

  • 03 of 10

    The oven switch is off

    One of the most common (and embarrassing) reasons the oven won't run is because it was accidentally turned off. There is usually a switch on the side of the stove. Make sure the switch is in the ON position.

  • 04 of 10

    Oven filter clogged

    Believe it or not, running your oven with a severely clogged oven filter often can do more damage than just circulating dirty air around your home. It can also cause the furnace to overheat and often turn a safety switch - called a high temperature limit switch - on and off, ultimately causing the limit switch to fail.

    Check your filter, which can be either a fiberglass or paper media oven filter, or a high efficiency pleated paper media oven filter, and replace if necessary.

    After replacing the clogged oven filter, turn the oven off for 10 minutes and then turn the oven switch back on. This should reset the oven electronics in the computer controlled ignition module.

  • 05 of 10

    Faulty high limit switch

    Note: If you've gone any further at this point or in this tutorial, you'll need to remove the front of the oven cover. Therefore, make sure that the power supply to the furnace is switched off at the corresponding junction in the main switchboard when the front cover of the furnace is removed.

    The high-temperature limit switch is a safety device that monitors the inside temperature of the furnace and switches off the gas valve to the burner if the temperature limits are exceeded. As soon as the temperature has dropped to the lower limit of the switch, the switch lets the gas valve start up again so that the burner can work again.

    As mentioned on the previous page, the high temperature limit switch can be damaged if it trips frequently due to overheating and low airflow from a severely clogged air filter. A heavily soiled air filter causes low airflow and heat build-up in the vicinity of the combustion chamber, which means that the switch is switched on and off frequently. This will eventually result in the switch failing completely from frequent overheating or getting stuck in the off or "idle" position.

    You can test the switch by using a multimeter to check for continuity:

    1. Set the multimeter to ohms (resistance).
    2. Disconnect and write down the wires leading to each switch terminal.
    3. Place a probe on each of the two switch ports on the faceplate of the switch on the outside of the oven.
    4. If the resistance is 0 ohms then the switch is good, if the resistance is infinite then the switch is bad.
    5. The exchange is easy, simply unscrew the circuit board and replace it with the appropriate replacement part.
  • 06 of 10

    Electronic ignition: Faulty detonator close to the surface

    Your highly efficient kiln most likely uses a special electronic ignition device called a "Hot Surface Ignitor" (HSI) that may be cracked or broken.

    The HSI is usually made of a material like silicon nitride or silicon carbide (more fragile), and when electricity flows through the igniter it gets hot and glows red when 120 volts is applied - similar to an incandescent lamp. The hot surface igniter is placed in the gas stream entering the burners to ignite the fuel gas.

    Under normal conditions, the HSI should last three to five years. However, it will eventually crack and will need to be replaced - faster if the oils from your skin get onto the item through improper handling. These hot surface igniters cost anywhere from $ 25 to $ 50 depending on your furnace model.

    These, too, are easy to replace and are usually attached with a screw or clip. Remove the connector and cables and replace them with the appropriate replacement part. Be careful not to get any oil from your hand onto the filament.

  • 07 of 10

    Electronic ignition: faulty flame sensor

    The KIS is supplemented by the electronic ignition system Flame sensor, with which the correct burner operation is determined. As soon as a correct flame is detected by the flame sensor, the HSI is switched off.

    You should note that on some furnace designs, the HSI will also act as a local flame sensor instead of having a remote sensor rod in the burner flame as the above photo shows.

    The flame sensor can sometimes fail due to corrosion; at other times it just dies like any other piece of hard-use equipment.

    Fitting a detachable flame sensor is an easy repair. See "Replacing an Electronic Flame Sensor" for more information.

    You can also try removing and cleaning the flame sensor using just emery cloth or fine steel wool like # 0000.

  • 08 of 10

    Faulty pressure switch

    The furnace pressure switch is another device to check. The pressure switch is a safety device located near the air supply motor that will prevent the oven from operating if proper vent air pressures are not detected.

    Sometimes it stays open or may fail because the exhaust vent is improperly vented, clogged steam traps, clogged switch lines, or other reasons.

    To test the switch, see the "Troubleshooting an Oven Pressure Switch" tutorial.

    Also check to see if there is a clogged hose connection at the draft outlet or cracked or broken hoses from the pressure switch to the draft outlet or condensate collection chamber, which could result in a tripped switch (fault).

  • 09 of 10

    Clogged condensate line to the floor drain

    A seemingly remote problem is a clogged condensate drain line (see photo). A blocked line can cause the pressure switch to fail as the pressure switch detects the accumulation of condensate in the furnace drain pan. The furnace only works when the condensate drain is free and the condensate flows freely.

  • 10 of 10

    Prohibited exhaust pipe

    Finally, another seemingly distant problem that can indirectly get the stove working can be a clogged or clogged smoke flue pipe. A blocked exhaust gas line can also trigger the pressure switch.

    Make sure the pipe is properly sloped and clear of any obstruction.