GP51MP-24B-045-1 Hot Surface Ignitor replacement

Discussion in 'HVAC Heating & Cooling' started by Onkar Sharma, Nov 4, 2017.

  1. Onkar Sharma

    Onkar Sharma Member

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    Nov 4, 2017
    Location:
    Massachusetts
    Hi All,
    Let me start by saying that I am very new to this.
    I just bought my house and woke up to a cold home. I am good with tools but am just figuring out the furnace.

    There is no ignition in the furnace. It looks like the signal from thermostat is reaching the furnace and the furnace does try to start and quickly errors out. From the flashing lights on the furnace logic board it looks like the ignitor needs to be replaced. I am trying to get the burner box cover off. I removed the 4 screws on the front cover but it is still stuck very tight. Is there a reason for the cover to be glued to the box? Should I just keep yanking at it or there is a trick I am missing?

    Sorry for the silly question but any help will be appreciated. Also I did unplug the HVAC and closed the gas line. Is there any other safety step I am missing?
     
  2. Stuff

    Stuff Well-Known Member

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    Mar 7, 2013
    Location:
    Pennsylvania
    I never heard of one being glued shut. Heat issues would make any glue ineffective. Sometimes rust will hold things in place but more likely there is another screw.
     
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  4. Onkar Sharma

    Onkar Sharma Member

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    Location:
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    Thanks.
    Makes sense except I see only 4 screws. Online video talks about only 4 screws.
    Here's the picture of my HVAC burner box cover

    Let me know what you think. Meanwhile I will try again tonight
     

    Attached Files:

  5. Stuff

    Stuff Well-Known Member

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    Yes, that cover should just pop right off. Did you use a multi-meter (ohmmeter) to check the ignitor?
     
  6. Onkar Sharma

    Onkar Sharma Member

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    I will tonight. I will retry taking the cover off
     
  7. Onkar Sharma

    Onkar Sharma Member

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    It is the same video I saw. That cover came off so easily for him. I think I broke a nail or two trying to pry it off. Am going to go there soon. Will keep you posted.
     
  8. Onkar Sharma

    Onkar Sharma Member

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    Checked igniter. It is reading 14ohms. The expected resistance should be between 10-20 ohms. Now I am at a loss.
    The two lights ds1 and ds2 are flashing fast alternatively.
    How do I check ground?
     
  9. Stuff

    Stuff Well-Known Member

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  10. Onkar Sharma

    Onkar Sharma Member

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  11. Onkar Sharma

    Onkar Sharma Member

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    It is fast flashing.
    I will try to measure the ground today and let you know tonight.
     
  12. Onkar Sharma

    Onkar Sharma Member

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    Nov 4, 2017
    Location:
    Massachusetts
    Hi Stuff,
    So the measurements are:
    1. Hot and Chassis- 125V
    2.Line and neutral- 125V
    3. Ohms between neutral and ground- ~1 ohms (sometimes read as much as 2.7-2.9)

    I have a new igniter. Ohms is 15.1.

    I am thinking logic board. Let me know what you think. I still have not been able to pull the darn burner cover off. I will keep trying.
     
  13. Onkar Sharma

    Onkar Sharma Member

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    Attached Files:

  14. Stuff

    Stuff Well-Known Member

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    Ohms between neutral and ground should be a fraction of an ohm and should not fluctuate. Try measuring again with the breaker in the electrical panel off.
     
  15. Onkar Sharma

    Onkar Sharma Member

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    I measured again more carefully. This time it was around 0.2-0.3 ohms.
    Let me know.
     
  16. Stuff

    Stuff Well-Known Member

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    Check the connectors that feed the ignitor. Disconnect and reconnect the 4 pin white connector on the board. Otherwise may need a new board.
     
  17. Onkar Sharma

    Onkar Sharma Member

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    Location:
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    OK. Thanks for all the help. I will check the ignition connection later tonight after I put my son to sleep.
    I tried to look up the board number. I am coming up with 83M00. Where is it written on the board?
    Should I just order the original (it is a white Rogers) or go with alternate part (21D83M-843)?

    I will update soon
     
  18. Onkar Sharma

    Onkar Sharma Member

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    Another problem is that I measured the voltage at the furnace to be 28 v.
    At the thermostat it drops down to 16v. I will look for any wire splitting, but I know nothing about how this house is wired.

    Kindly advise.
     
  19. Stuff

    Stuff Well-Known Member

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    Original should be 69M1501 - number printed on white sticker on IC (Integrated Circuit). The 83M00 looks to be a newer equivalent Lennox version. Also is W.R. 50A66-743 which is same as 21D83M-843 but without the extra adapters and parts that you wouldn't need.

    Voltage drop at thermostat would be independent of your issue. Disconnect the thermostat and see if the voltage goes up. Thin wires, distance, and load all play a part.

    Still might be something else but replacing the board is the next logical step.
     
  20. Onkar Sharma

    Onkar Sharma Member

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    Thank you very much.

    Considering that it is going to be considerably colder over the next 2 days, I ordered 21D83M-843, more expensive but was available with 2 day shipping.The other one was cheaper by 40 dollars but was coming in on Tuesday.
     
  21. Stuff

    Stuff Well-Known Member

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    One more test. Unlikely but still something to check. Disconnect and measure resistance of ignitor leads to ground. Should be close to infinity.
     
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