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Dirty Flame Sensor Problem

It really is typical this seasonal time of year to note that your furnace is switching on and off two or three times for very brief runs. Then subsequent to the three attempts, the furnace shuts down for about an hour or two. After this wait period, the furnace attempts to start-up again. So why is my furnace not staying on? Maybe or maybe not your flame sensor may perhaps be the problem. Do I have an unsatisfactory flame sensor? Maybe you have a dirty flame sensor. This is very common for furnaces which may have not had a optimization or regular maintenance in the previous Two to five years.

What exactly ought I do regarding a dirty flame sensor?

Get a service technician clean and check your flame sensor. It might require replacing or only a cleaning, depending upon the problem. Typically either one of these solutions will likely be a relatively cost effective repair. Cleaning and checking the flame sensor should really be a regular element of a yearly maintenance tune up. Call Alexander Heating and Air for a tune up or acquire an annual service contract and feel confident of how your furnace is in great shape.

Warning: most furnace repairs involve high voltage and flammable gas. It is strongly advised you don’t perform this yourself. Have a skilled HVAC technician check and clean your flame sensor.

Just what is a flame Sensor and are they all necessary in my furnace?

The flame sensor is one among the many safety features inside of a gas furnace. There are some being checked right before the gas is allowed to burn and some right after the gas is burning. Those that are checked right after the gas is burning are available to safeguard you and your home from dangerous conditions while your gas is burning. The flame sensor is just one of those safety measures. The flame sensor is constructed out of metals that will create an electrical current if in the presence of a flame. It is usually meant to shut the product down when not enough burning fuel is detected from the last burner in the gang of burners inside the furnace. A constant flame from the last burner would indicate a reliable burning environment and also that the whole set of burners are getting approximately the very same amount of fuel and air. If no flame is there, then any one of the burners inside the group could possibly be burning fuel in an unsafe way. Therefore the system checks for the flame and closes the fuel valve when no flame is detected. Any system can have a false reading, so the control board usually tries to light the burners two more times. If these three times the system delivers the same message that the flame sensor isn’t detecting a flame, the whole furnace is shut down via the control board either for a couple of hours or completely until reset by a service technician. This is called a lockout condition.

What triggers flame sensors to malfunction?

You can find two possible challenges with flame sensors. A dirty flame sensor could be the most likely problem. At this point it is essential to understand that burning fuels do produce trace amounts of water when burning. And whenever water contacts most metals, the metals usually rust. This is also true with flame sensors. The metal end of a flame sensor can rust after a while. The rust accumulates and prevents the flame sensor from producing the current that tells the control board which it detects the flame. The other possible concern is that the flame sensor is now bad. This is usually a cracked insulator or perhaps short in the electrical components. Replacement is suggested for a bad flame sensor.

If you think you may have a problem with your furnace,

call The HVAC Guy at Alexander Heating and Air Conditioning.

For Quick,  Honest and Affordable  heating system services.

1-919-886-HVAC (4822)

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10 thoughts on “Dirty Flame Sensor Problem

  1. Julio gaitan

    My rheem furnace malfunctions about every 2 weeks . it will all of the sudden blow only cold air . I will manually switch off the furnace and switch it back on and this is what it does. It does everything normal up to the igniter working no flame so it pauses a couple of seconds and igniter turns on but again no flame but this time the blower turns on and throws cold air , I’ve noticed that after turning off the power and turning it on after an hour or two then it works normally , do you have any advice on how yo fix the problem

  2. Julie

    Hate to ask but extremely frustrated, I’m a renter and my landlords thankfully have a protection plan on my furnace however; at LEAST once a year parts need replaced which I’ve been told are now obsolete, today alone I’ve had tech here 2 and now will need to wait until am due to furnace keeps trying to turn on but sometimes either just instantly shuts off or is running but no air (warm or cold ) is happening, sometimes it literally clicks every 1/2 second. Heard them say could be getting dirty gas? I don’t know what that exactly means but with a child I don’t like the sound of anything dirty trying to push through our furnace, they cleaned sensor but within 6 hours I’m back to same clicking issue and no heat, what does dirty gas mean and/or is there something I can/should do? Please help

    1. thehvacguy Post author

      Hate to say but just not enough information to give you a decent answer. It could be any one of several things as the symptoms are all the same. But dirty gas? That sounds very far fetched. There are traps and filters that are put in the gas pipes to prevent that. As far as safety concerns about dirty gas, nothing to worry. It will only affect the valves and cause them to malfunction. Not a safety issue. More than likely it is an internal issue and I say this because you said the furnace is obsolete and parts unavailable. That would only tell me that the furnace is over 20 years old. In which case there are numerous items in your furnace that can cause the same symptoms. replacement is the only real solution.

  3. Mary Justen

    My flame sensor has been cleaned 4 times & I want the problem resolved.
    My repairman is saying that it might need a new circuit board (about $500).
    Is this likely or would just replacing the sensor fix the problem?
    Any help will be appreciated.

    1. thehvacguy Post author

      Has he checked the micro amps DC on the flame sensor? If it is pulling 4-5 mA then the flame sensor is not the problem. It could be something else. The circuit board is expensive. But I would need to know more, like what is the error code the board is detecting?

      1. Brandon R.

        I am having a heating problem myself, I have done some research trying to trouble shoot this myself. I pulled my flame sensor out to find the ceramic was broken and the rod would spin freely in the ceramic collar. I replaced it and still the same result. I did test the Micro amps and would read 1.8-3 micro amps for a second or 2 then it jumps to 5.0-5.5 and shuts off. It then repeats 3 more times and then the lock out occurs. I have also check continuity of many wires ONE at a time and putting them back where I found them ONE at a time. Everything is checking out. I am concerned that it is the circuit board since everything else seems to be working.
        In case you want to know the exhaust fan for the gas spins up every time it prepairs to light and continues till the furnace does its lock out. The cold air works, the main squirrel fan for the furnace vibrates as if it is out of balance (I feel I need to pull it out and clean it). I have a clean filter that I replace on the first of every month.

        I have a Carrier furnace 58pav070-12 it is about 16 years old, the circuit board is 1012-940-j.
        When I did apartment maintenance this would be the time I call a service tech out, I do not have it in my budget yet to call a service tech and it is getting colder. If you could point what to look at next I am all ears.

      2. thehvacguy Post author

        The circuit board should be blinking a specific sequence of blinks which will identify the issue the board is reading. Count the blinks then check it against the chart on the inside door to the furnace. This will give you direction on where the issue may be. If the sensor is correct, then the board or wiring may need to be replaced.

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