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Problem: The heater comes on, the gas lights, the furnace warms up, the blower starts then abruptly the gas cuts off.

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Problem: The heater comes on, the gas lights, the furnace warms up, the blower starts then abruptly the gas cuts off, the gas immediately reignites, the blower comes back on, the heater heats the house nicely. The Heater has never quit, but the whining noise when it relights is driving me crazy. I’ve replaced the ignitor and flame sensor with parts from Arnold in the last two weeks. The flame sensor helped in that the heater now occasionally runs normally, no second lighting of the gas. I’m very handy and have a professional Volt-Amp meter. I’m stumped.

Answer and Possible Solution: Thanks so much for your business and interest in our website! This sounds like you have a furnace short cycling problem. We have a really good YouTube Video below that shows why gas furnaces short cycle. We have this question asked many times and the question is “Why does my furnace keep shutting off before the desired temperature on the thermostat is reached?” My suggestions would b to test the limit, pressure switch and rollout switches to make sure they are staying closed when the burners kick out. If one of these opens then this would cause the erratic operation of the gas going off and on. If these safety controls all check out OK, then I would suggest taping your furnace door shut and make sure you are getting a constant 24 to 28 volts between the W and C (com) wires coming from the thermostat. If the voltage drops out when the gas shuts off then you have a thermostat or a thermostat wiring problem (short in wires). If you are getting a whining noise I would look at the gas orfices and burners to make sure they are not dirty or partially stopped up. This could also be caused by too much or too little gas pressure. Most of the time it is too much gas pressure. This could also be the problem of the gas shutting off if the flame sensor is not engulfed in a nice blue flame when the burners immediately ignite. If there is too much gas pressure, especially when the furnace is cold the burners will not light properly and the flame sensor might not sense the flame right and cut the burners off. You might need a new furnace flame sensor. Please click here if you are interested in seeing the furnace flame sensors we sell.  Please send me you furnace’s model number if you would like for me to find out which flame sensor part number or part your furnace uses. Our email address is: arnoldservice@gmail.com Best of luck in finding the problem. I hope you have a blessed day. Thank you so very much for your business!

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19 thoughts on “Problem: The heater comes on, the gas lights, the furnace warms up, the blower starts then abruptly the gas cuts off.

  1. Typo correction on ‘my symptoms:’
    my symptoms:
    furnace comes on, flames comes on, and then furnace turns off and blower kicks in and continues, OR blower kicks in for only 5s and furnace turns off while blower continues. Either case blower stops after 2 mins, and immediately when blower stops the furnace comes on again. Then this cycle simply repeats.

    1. Hi Michael! You will need to test with a voltmeter to see what is cutting the furnace off. If this is a flame sensing problem or a control board problem then this can be hard to troubleshoot. What you can do is make sure that you are getting 24 volts constantly with no interruptions between the W and C (com) terminals on your control board. If the connection between W and C is interrupted then you probably have a thermostat problem. Make sure the batteries in your thermostat are good. Make sure all your safety controls like the pressure switch, limit, and rollouts are all staying closed when the burners go off unexpectantly. I would like to suggest that you clean your flame sensor and make sure all wire connections are good and tight. We have a post about a similar problem you are having on the following page: https://arnoldservice.com/problem-your-furnace-main-burner-ignites-the-main-burner-stays-on-for-8-to-10-seconds-then-shuts-right-back-off/ If everything checks out OK then you might need a new control board to solve your problem. I hope you can find something soon that will help you solve the problem. Steve

    2. It’s also possible if unit has older thermostat that heat anticipator is set wrong and causing short cycling. Reset to amperage of low voltage heat amperage. Normally 3-7amps.

      1. Yes! Very good advice. Yes, I have seen anticipators on old thermostats cause short cycling problems. Thanks so much for your comment! Steve

  2. Hi. I have a Kingsman fireplace that heats up, comes to temp. like it should. After a minute or so , it will reignite then go out several times until it finally settles down. Any info would be appreciated. Thanks.

    1. Hi Glenn! I am very sorry, but I do not know anything about Kingsman fireplaces, but it does sound like you are having a flame sensing problem. About all that I could suggest that you do would be to check all connections to make sure they are good and tight. Also, clean the pilot and flame sensor if the fireplace has a flame sensor. Some of the fireplaces have a millivolt pilot generator. If the pilot flame is not really hot on the millivolt pilot generator the pilot will not produce enough voltage to keep the gas valve open and this could be the problem. Here is a really good Youtube video on How Millivolt pilots work: https://www.youtube.com/watch?reload=9&v=riaN_j5tmX4 I hope this helps you find and fix the problem soon! Steve

  3. What would cause the burner to momentarily shut off and then re-ignite during the heating cycle? After the burner ignites and the blower starts, the burner shuts off after about 1 minute or so and then re-ignites within 5-10 seconds. Sometimes this happens several times before the burners stay lit and the heating cycle completes. The furnace does not shut off until the thermostat is satisfied. Replaced the flame sensor and checked the voltage & ground all of which is ok. This happens mostly after the furnace has set idle for several hours (like overnight when the thermostat is set at a lower temperature) and then is running when the thermostat temp is raised in the morning to begin heating the house. It may do this 2-3 times during each warming cycle until the house temperature has evened out and the heating cycles are further apart. The only way I know this is happening is if I’m standing near the furnace, which is in the attached garage, when it is running. Otherwise you would not notice any issues with the furnace operation or house temperature while inside the house. Could this be a control board issue?

    1. Hi Kraig! There could be one of several things that could cause the furnace to cut off in the mid of a cycle. The hard thing is being there to test with a voltmeter when the problem occurs. This could be your thermostat that has low batteries and is cutting the 24 volts off between the W and C (common) wire. Make sure you are getting a constant 24 to 28 volts between W and C from your thermostat. A pressure switch could be opening up. Make sure your pressure switch is staying closed all the time when the draft inducer is running. Make sure that your limit is staying closed. Make sure all wire connections are tight especially any ground wires. This sounds like you are having a flame sensing issue. Make sure that your flame sensor is sitting in a nice blue flame. You might need to clean your burners. If all this checks out OK then I would think that you have a control board problem. I hope you can easily find and fix the problem. Steve

      1. Thanks for the suggestions Steve. The furnace is only a year old so everything is in top shape. I did replace the flame sensor just in case but it didn’t help. The ground connections check out as do the pressure switches. I am now suspecting a flaky control board as well since all of the other components seem ok. As I mentioned the furnace heats the house just fine; it’s just that this intermittent burner problem is troublesome. The furnace never shuts down while the burners stabilize, it just isn’t normal for burners to shut off and then re-ignite. This never happens during the initial ignition, only after the blower comes on and then goes away after the furnace has gone through several heating cycles. I’ll try a new control board as all components are still under warranty. Thanks again for considering my question.

      2. Yes, if the limit and pressure switch are staying closed when the gas cuts off then I guess your only option is to try a new control board. I am glad to hear it is under warranty. I hope you get it fixed soon! Steve

  4. Have an old moncrief furance. As soon as the blower starts it shuts the burner down. Replaced the fan limit switch nothing changed.

    1. Hi Tom! I really do not have any other advice on what the problem could be other than what is listed in this post. Sorry that I can not give you any more advice. Steve

  5. Hi Steve,
    On our 7 year old Goodman 95% furnace, when the blower comes on, the gas flame shuts, while the blower continues to run, blowing cold air. Any thoughts?
    Regards, Norbert

    1. Hi! I would like to suggest that you try and clean the flame sensor. I would also check to make sure that the pressure switch is staying closed the whole time the draft inducer is on. We have a post about cleaning the flame sensor on the following page: https://arnoldservice.com/problem-your-furnace-main-burner-ignites-the-main-burner-stays-on-for-8-to-10-seconds-then-shuts-right-back-off/ I hope you can easily find and fix the problem. Steve

  6. i lose pilot and burner flames after blower starts

    1. Hi Jim! I would like to suggest that you check all your safety controls like the pressure switch, rollout switches and limits to make sure they are staying closed when the flames go out. Some control is cutting the gas valve off when the blower comes on and you will need to find out which control is doing this. I would suggest making sure all connections are good and tight. We have lots of furnace troubleshooting advice on the following page: https://arnoldservice.com/gas-electric-furnace-troubleshooting-simplified-2/ I would suggest going through the troubleshooting flow chart to see what is wrong: https://arnoldservice.com/wp-content/uploads/2014/12/furnace-troubleshooting-flow-chart.pdf We also have lots of troubleshooting questions and answers on the following page: https://arnoldservice.com/furnace-troubleshooting-questions-answers-index/ If you have any specific questions please let me know. Thanks! I hope you can easily find and fix the problem. Steve

  7. Please feel free to comment if you have any other recommendations on what might cause this problem with the gas cutting out when the blower comes on.

    1. If its a high effency unit check for water buildup in pvc vent,drain blocked or ice buildup if draining outside.safety switch will shut burner if it detects any blockage.I kn
      ow happened to me twice!!!!!

      1. Hi Michael! Thanks so much for taking your time to share how you fixed your furnace! God bless you. Steve

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