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York Furnace intermittently blows cold air

OllieW
OllieW Member Posts: 6
edited December 2020 in Gas Heating
Hi brilliant people,
I have a mystery case with my furnace and I hope you could help me solve it.

Long story short. I have York furnace TG8S 80% AFUE that has been used for 5 years. A few weeks ago, it started intermittently fail to ignite and blow cold air. It happens at least once per day. If I turn down the thermostat so the furnace stops, and turn the temp back up again, it would work completely normal again for a few hours.

When it stops working, the furnace gave me error code 7, which is "flame could not be established during three trials for ignition. Check that the gas valve switch is in the ON position. Check for low or no gas pressure., faulty gas valve, dirty or faulty flame sensor, faulty hot surface ignitor, loose wires, or a burner problem."

When it's faulty, I noticed that my induced will come on, the hot surface ignitor lights up, the gas valve opens and gas comes out (I can smell it), but no flames are established. Then it retries three times, and eventually fails and starts to blow unheated air. HOWEVER, it's working the majority of the time and the ignition processed could be completed just fine...

I have checked loose wires, everything is connecting well. So I'm really out of ideas. Thank you for reading my story and I'm looking forward to getting some ideas from you! Thanks!

Comments

  • PC7060
    PC7060 Member Posts: 1,443
    Sounds like you have a bad igniter. Easy item to replace. 
  • OllieW
    OllieW Member Posts: 6
    edited December 2020
    Thank you for the thought. I ordered a new igniter and installed it. It would ignite okay but the fan would not turn on following that... Maybe the model of the new ignitor doesn't match. Any other thoughts in addition to the igniter problem?
  • mattmia2
    mattmia2 Member Posts: 10,930
    something dirty or clogged in the burner so the passages that direct the gas toward the igniter are clogged. Igniter got moved to the wrong position somehow. Some problem with the draft so the gas isn't making it to the igniter or it isn't getting mixed with air when it gets there. Clogged orifices or a problem with a regulator or gas supply or the valve so it isn't getting enough gas to light properly. If you don't see something clogged with the small passages and pinholes in the burner it is probably time to find someone who is good with checking and adjusting combustion and draft.
  • HVACNUT
    HVACNUT Member Posts: 6,331
    @PC7060, when was the last time you saw an intermittent HSI failure? Unless is was a weak ground or molex connection, but that wouldn't necessarily need a new igniter. 
    The OP needs a pro on site.
    PC7060
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,477
    Agree with @HVACNUT If the igniter glows it's not defective. The op smells gas when it doesn't light.
    Dirty burners or hx dirty or flue could be an issue.
    Time for a pro
  • JUGHNE
    JUGHNE Member Posts: 11,276
    I have seen defective HSI's just barely glow, not enough to light.
    Or low voltage from the board.

    IMO, if you remove the furnace burner door and turn off the lights you should see the glow across the room.

    Does it glow that much?

    If so you still need a Pro, clean flame sensor while in there also.
  • OllieW
    OllieW Member Posts: 6
    Thank you guys so much for the thoughtful input!
    I'll be honest, I had a pro came over, and he just told me that I need a new furnace (again my furnace is 5 years and still works mostly okay). Then the furnace installation people came over and were nice enough to take a look, and said I don't need new furnace, and they think it's the rollout switch/pressor switch problem. But my ignitor light up so it's probably not the pressure switch and the flame is bright blue when it lights up so I doubt it's the rollout switch...
    Is it time for me to find a third pro to take a look...? (Cry laugh face)
  • mattmia2
    mattmia2 Member Posts: 10,930
    Yeah, you need to find someone that knows what they are doing. is there anyone near you in "find a contractor"?
  • mattmia2
    mattmia2 Member Posts: 10,930
    there is a remote possibility that a cracked heat exchanger could cause this, but it most likely would only cayuse this particular problem if the blower was running when it tried to light
  • HVACNUT
    HVACNUT Member Posts: 6,331
    Different manufacturers use different circuit boards and some go through a different sequence. 
    The 120v circuit will energize the inducer fan, then igniter. 
    The 24v circuit will make sure all is safe before energizing the gas valve. 
    The 120v circuit doesn't even know there is a gas valve, it's just doing what its told so the igniter can still receive power even if a safety is open.

  • mattmia2
    mattmia2 Member Posts: 10,930
    Probably should put a voltmeter on the gas valve to make sure it is staying energized when it fails to light but you smell gas. There could be a problem with the valve or regulator or orifices such that you get some gas but not enough to light properly as well.(has anyone cleaned the burner yet?)
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,477
    Should pull and clean the burners and check the draft. HS ignitors are usually good or bad but I suppose anything is possible.

    I have seen roof top units (Trane) with HSI where the job had 208 three phase and no one changed the transformer taps from 240 so the ignitor was getting 90-100 volts and was marginal

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