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  1. #1
    Join Date
    Feb 2008
    Location
    Kent, Ohio
    Posts
    10

    Exclamation Pilot light keeps shutting off

    Very sorry for the long post but since this is a complex problem I wanted to be thorough in my description


    I have an older HEIL EG100-1 Natural Gas forced air furnace in the garage in a house I just bought about a month ago. This furnace was rarely used (from what I can tell) by the previous homeowner. The furnace employs an oldschool standing pilot light with thermocouple right beside it.

    Here's the problem:

    The pilot light goes off after one heating cycle.

    Here's the order in which it all goes down...

    1. I light the pilot with the red button depressed
    2. The pilot lights and heats up the thermocouple
    3. I let go of the red button and the pilot stays lit until I call for heat from the thermostat
    4. The burners kick on and after the plenom gets hot, the blower blows the hot air out
    5. The thermostat heats to the temp I have set it at sending a signal to gas valve to shut the burners off
    6. The burners go out but the blower is still running
    7. The pilot light goes out by itself (happens at random times but usually after the burners are shut down by the thermostat control)

    I don't know why this pilot is going out by itself.

    I have changed the thermocouple and since the unit kicks on after lighting the pilot, I assume that this brand new thermocouple is functioning correctly.

    I have also used a multimeter to verify that the thermostat is functioning correctly. It is and 24 volts are supplied to the gas valve when called for.

    Possible reasons I can think of for the pilot valve to go out:

    1. I have cleaned the end of the pilot valve and replaced the thermocouple. The pilot flame looks large enough and the flame hits the end of the thermocouple directly.

    2. There are no drafts around where the pilot is located to blow it out.

    3. Gas is being supplied to the pilot as well as burners because it kicks on initially.

    4. Thermostat is functioning correctly (verified with multimeter) but shouldn't have any effect on pilot light anyway.

    5. Just for good measure, I've replaced the dirty air filter with a new one.


    Do I need to get another gas valve? These things are incredibly expensive from what Ive researched. Is there any way to remove and clean the Gas valve? This furnace has not been used for a while and I suspect some spider nests or other debris in the gas valve itself.

    Any suggestions before it gets wicked cold would be greatly appreciated

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Pilot light keeps shutting off

    Assuming itís the correct thermocouple there could be a problem with the gas valve or external drafts.

    As the thermocouple heats up, it produces a small amount of electricity and when it gets hot enough from the pilot sends a signal to open the gas valve by using a solenoid operated by a 24 volt transformer.
    As long as the heat is enough and constant this will keep the valve open to maintain the pilot light to stay lit.

    A natural gas flame should be a bright blue with the tip of the flame having just a tinge of yellow.
    The flame should be strong enough to hit the thermocouple tip about 1/2 inch from the tip end.

    A yellow flame is caused by lack of air and incomplete combustion. It can be caused by a dirty pilot tube tip

    A split flame is caused by dirt in the pilot tube. Take a needle or small nail and gently clean the tube

    If the flame is weak or shaky looking, check to see that a breeze or draft is not blowing on it.
    Anything like a back draft or blower disturbance of the pilot flame can make the pilot go offÖ.. check the pilot flame with the burner off and the blower on, see if it flutters.

    A hole in the heat exchanger can cause blower disturbance since the blower will run for awhile after the burners shut off.

    Observe the pilot flame when the burner goes off, see if it might suck out.

    When it comes to a gas furnace I donít feel this is really a DIY job to change gas valves unless you are very competent and should be left to a HVAC technician.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Oct 2009
    Posts
    1

    Default Re: Pilot light keeps shutting off

    I'm having similar problems to the original poster, but the reply doesn't seem to have the right answer for me.

    I light the pilot, then the thermostat calls for the furnace to heat up. The burners kick on, and the blowers kicks on. After they get to the desired temp, and you can hear the audible "click" of the burner valves shutting off, the blower will blow the rest of the hot air out. While that is happening there is a second "Click" that blows the pilot out.

    What could be causing this? The furnace is a Coleman Evcon Presidential and we live in a mobile home.

  4. #4
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Pilot light keeps shutting off

    To the first post, as Canuck said because it is intermitant it sounds like there is a crack or hole in the heat exchanger that's blowing the pilot out or dirt in your pilot tube. The pilot tube should be taken off and cleaned, blown out with nitrogen. With that being said the blower in your furnace should run for a short time after the Heat cycle to cool the Heat Exchanger. If this did not happen the heat from the Heat Exchanger would cause the furnace to go off on High Limit.
    To the second post, does it happen all the time? If it does not happen all the time it could be a downdraft or your thermocouple or your gas valve.

    Any work done on Gas Furnaces or any Gas Appliance should be done by a properly trained person in the HVAC field or the Gas Co. I live in MA. and about a year ago a person in Scituate called the Gas Co. due to no heat but couldn't wait. He blew his Girlfriends house up with him in it, unfortunately he was killed. Good Luck!!!

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,557

    Default Re: Pilot light keeps shutting off

    Another thing that can cause this problem is an improperly installed flue pipe.Most newer furnaces only require a 3 or 4 inch flue. Running that size flue into a large chimney does not provide enough up draft and when the heat cuts off you will get a sudden down draft of cold air from the chimney that will blow the pilot out.

    Sidarian,
    The second click suggests that the unit may have an oxygen depletion sensor and is shutting off the gas to the pilot. This is usually caused by a dirty OD unit and can usually be cured by blowing out the pilot light orifice. Pick up a can of air sold most computer stores for cleaning computers and leave the pilot off long enough to cool down. Insert the tube of the caned air in the end of the pilot tube and give it a couple of blasts then relight.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: Pilot light keeps shutting off

    You should remove your pilot tube before blowing it out, leaving it in place will only push the crud back towards the gas valve and cause more problems or the crud will work it's way back to the opening and you'll be back where you started.

    Any work done on Gas Furnaces or any Gas Appliance should be done by a properly trained person in the HVAC field or the Gas Co. I live in MA. and about a year ago a person in Scituate called the Gas Co. due to no heat but couldn't wait. He blew his Girlfriends house up with him in it, unfortunately he was killed. Good Luck!!!

  7. #7
    Join Date
    Sep 2013
    Posts
    1

    Default Re: Pilot light keeps shutting off

    I hope someone is still reading this thread.

    I have a old forced air gas furnace.

    My pilot light, lights fine, stays lit fine as long as the burner do not start. Once the burner starts and completes a cycle the pilot light goes out with the burners. It appears that gas is shut off to the pilot light the same time that gas is shut off to the burners. Meaning the flame dies gradually as does burners.

    Fixes I have tried:
    1. replaced thermocoupler twice.
    2. blew out pilot light gas supply tube from the gas valve side (compressed air).
    3. assured that pilot light is striking the thermocoupler mid-length and that the flame is blue.

    I am afraid that Combination Gas Valves needs replacing.... any advice or thoughts are welcome...

  8. #8
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: Pilot light keeps shutting off

    Quote Originally Posted by ppyept View Post
    I hope someone is still reading this thread.

    I have a old forced air gas furnace.

    My pilot light, lights fine, stays lit fine as long as the burner do not start. Once the burner starts and completes a cycle the pilot light goes out with the burners. It appears that gas is shut off to the pilot light the same time that gas is shut off to the burners. Meaning the flame dies gradually as does burners.

    Fixes I have tried:
    1. replaced thermocoupler twice.
    2. blew out pilot light gas supply tube from the gas valve side (compressed air).
    3. assured that pilot light is striking the thermocoupler mid-length and that the flame is blue.

    I am afraid that Combination Gas Valves needs replacing.... any advice or thoughts are welcome...
    This is an old post, you could have started a new post...by anyway:
    If I were fixing your heater (I assume it's the furnace), I'd start with your gas valve. Unfortunately, replacing a gas valve is not a DIY project. Call a plumber.

  9. #9
    Join Date
    Jan 2008
    Posts
    1,096

    Default Re: Pilot light keeps shutting off

    In a mechanical gas valve, if the new thermocouple doesn't fix it then it might be the regulator, and these are not intended to be serviceable outside of the factory that made them- you replace the whole unit as needed. You and your fire insurance company both want to have a licensed HVAC person take care of this for you, this is not in the normal range of DIY like a thermocouple is- any mistakes here can be deadly!

    Phil

  10. #10
    Join Date
    Oct 2013
    Posts
    1

    Default Re: Pilot light keeps shutting off

    Hi There, I have the identical issue you mention below, have you sorted the problem out. What was the solution. Did you have the gas valve changed.

    Thanks for responding.


    Quote Originally Posted by ppyept View Post
    I hope someone is still reading this thread.

    I have a old forced air gas furnace.

    My pilot light, lights fine, stays lit fine as long as the burner do not start. Once the burner starts and completes a cycle the pilot light goes out with the burners. It appears that gas is shut off to the pilot light the same time that gas is shut off to the burners. Meaning the flame dies gradually as does burners.

    Fixes I have tried:
    1. replaced thermocoupler twice.
    2. blew out pilot light gas supply tube from the gas valve side (compressed air).
    3. assured that pilot light is striking the thermocoupler mid-length and that the flame is blue.

    I am afraid that Combination Gas Valves needs replacing.... any advice or thoughts are welcome...

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