York Stellar Erratic Starting

Discussion in 'HVAC' started by bazza, Dec 9, 2008.

  1. Dec 9, 2008 #1

    bazza

    bazza

    bazza

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    I have a York Stellar gas furnace around 16 years old - model P3UCD16N07601A with an annoying starting problem - unfortunately it is intermittent. This is how the scenario usually goes when there is a problem. I call for heat, the system responds exactly as it should; it then runs for around 5 minutes then closes down. The (small) inducer fan continues to blow and the system goes into the re-try mode. Sometimes this will work and it reignites and continues to run until the temp has been reached but other times it does not and the inducer fan runs constantly. (I think it tries to reignite twice). If I then switch off the power and try again later it will sometimes work as required – but not always. I read the manufacturer diagnostics which seemed to indicate that the White Rodger ignition unit had to be replaced which I have done. Unfortunately the problem persists. The diagnostics that came with the new igniter appear to indicate a sensor or limit switch problem. I just don’t know where to start with this - any ideas.
     
  2. Dec 9, 2008 #2

    glennjanie

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    Welcome Bazza:
    Hey, its a bad time to have frunace trouble. You could start by looking at the inside of the cover panels for a wiring ladder; they usually have the ladder and a regular diagram. You can look at the ladder and track where the power goes and what it does at that point. Its an easy way to find limit switches and other small accessories. Then you can look at the wiring diagram to find the physical part's location.
    With the age of the unit, I would check the heat exchanger for leaks. The economic life of a furnace is generally around 12 to 20 years. If the heat exchanger is leaking, it may be time for a new furnace because of the expense. Heat exchangers are not cheap at all and usually break the 'economic' limit. Limit switches and iginters are within the limit.
    Glenn
     
  3. Dec 10, 2008 #3

    bacardi547

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    Bazza :
    Sounds to me like if you have a fairly simple problem. Inside the burner assembely there is a pilot light that only will come on on a call for heat . somewhere attached to that or attached to the burner itself will be a small metal rod this is what tells the ignition control module that there is a flame present . This rod can either be a straight rod or bent in an L shape but either way it will be in the pilot flame or the burner flame . after years of running this gets soot on it coating it from the heat and will cause your system to ignite then realizing that the temperature is not hot enough the unit will shut down. with a piece of 120 gritt sand paper brind the rod back to a silver look instead of the black . be sure to install it just as it was before you removed it . if you are uncomfortable with touching any of the gas components then try it while everything is still in place. hope that helped.
    brian
    p.s. I said in place I hope you realize with the unit saftley shut off.
     
    Last edited: Dec 10, 2008
  4. Dec 11, 2008 #4

    bazza

    bazza

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    Thanks Bacardi and Glen - I shall investigate this weekend and let you know the outcome
     
  5. Dec 15, 2008 #5

    bazza

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    Bacardi / Glen

    Well I followed your advice at the weekend - I have the original documents and wiring diagram etc so located sensors and limit switches - externally they all look OK as does the cleaned up flame/heat sensor. The furnace still continues to start but not reliably as it will often run for 5 minutes then the gas valve closes and the reignition will not work as the gas valve remains closed. if I then leave it to cool down it will sometimes start OK but not always. The trouble shooting diagram says I should test the limit switches (how do you do that ?) Do you think I should just replace the limit switch -and flame sensor. Could not see a manufacturer name or part number - any advice on where I should go to get replacements. The problem appears to be a simple component failure - that is difficult to track down. Can I provide any other information that might help to diagnose the problem.
     
  6. Dec 15, 2008 #6

    glennjanie

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    Hello Bazza:
    Limit switches and flame detectors are inexpensive parts that can be easily changed out. You could just keep changing parts unti it works.
    Glenn
     
  7. Dec 15, 2008 #7

    Jabber

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    I have a very similiar problem. I just talked to am HVAC friend and he suggested that I call the gas company. Here is my problem:

    Furnace turns on when there is a call for heat. Electric ignitor glows brightly, gas comes on. Ignites the gas, but it shuts off within a few seconds. Ignitor glows again, gas comes on, ignites for a few seconds and then shuts off. Does this about 3-4 times. It will do this mainly in the morning when the system is cold(er). We have an auto thermostat. However, if I force it to shut down and try to re-initiate the call for heat a few times, it will eventually light up.

    After describing the problem to my friend, he suggested I call the gas company and have them check the regulator. Maybe the system is not getting the right amount of gas, is sensing that, and shutting itself off..

    Don't know if this helps, but maybe it is a solution to your problem...
     
  8. Dec 15, 2008 #8

    glennjanie

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    Hello Bazza:
    Be forewarned, if you call the gas company with a complaint they will come out, shut off and seal your meter and tell you to call a Plumber to make the gas line right. They will not come back until the Plumber certifies there is no leak or problem with the gas.
    Glenn
     
  9. Dec 16, 2008 #9

    bazza

    bazza

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    Glenn / Jabber
    Thanks for the further advice however I have decided to pursue replacement of the flame sensor and limit switch, will let you know if this cures the problem.
     
  10. Dec 24, 2008 #10

    johnceberhardt

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    Mine does the same thing. Look at the pictures in my thread. Little blower always runs, igniter wire glows, ignites gas (nice flames), runs about 5 minutes, heats up the limit switch until it exceeds 200* and shuts the gas valve down-restarts cycle. I think it's the blower motor but i haven't had time to swap that yet. I connected the blower up to 120v and it doesn't seem to blow enough air volume through the ducts to keep the limit switch from tripping. It works but now well enough. No obstructions anywhere and the gas pressure is good. I think I just need a cheap motor now.

    And oooh it's soooo cold here. Never got above zero the whole last weekend. at least it's in the 20's now.

    My trane failed yesterday and had to mess with that on top of all this other stuff.

    JCE
     
  11. Dec 24, 2008 #11

    johnceberhardt

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    P.S. my old carrier weathermaker hasn't failed at all. I think i'll go give it a hug.
     
  12. Nov 27, 2010 #12

    Tiger81269

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    BAZZA,

    What ended up being the solution?
    My York just started doing the same thing a few weeks ago since turning it on and servicing the air filter. Since then it has worked a few times since I've been home (I travel a lot for work). But now that I've been home for a week it hasn't worked properly.
    Thanks for the coming reply.
     
  13. Dec 23, 2010 #13

    Dtodd

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    I am also having same intermittent problem with my York 15 year old York. Vent fan comes on, gas valve opens, spark igniter heats up, burners do not light all the way across, gas valve closes. Most of the time will stay lit on the 2nd cycle. If not, I have to turn off power. Works fine when power is turned back on. Heating contractor has changed control module, flame sensor, and burners.
    Voltages are all good, vacuum & vacuum switches are good. Contractor now wants to change out the gas valve?? Any thoughts would be appreciated.
     
  14. Dec 24, 2010 #14

    Tiger81269

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    My problem turned out to be a pluged water drain on the bottom half of the unit. Service Tech came and unbolted the lower electrical box, swung it out of the way to reveal a black box that a water tube ran into. It was full of water. He cleaned it out and removed the blockage. Furnace works great now.
     
  15. Dec 25, 2010 #15

    Dtodd

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    Had already checked the water drain as well as the vent fan intake and exhaust pipe for obstructions. Also checked the heat exchanger for cracks. and checked for carbon monoxide in the vent pipe.
    Service has now changed the gas valve as well but still having problem and are pretty much at a loss.
    York tech support has not returned phone calls.
     
  16. Dec 26, 2010 #16

    paul52446m

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  17. Jan 5, 2011 #17

    Dtodd

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    Thanks paul52446m.
    The gas valve & the electronic board have both been changed out.
    When it fails the gas valve stays open less than a second and the burner(s) nearest the flame sensor don't light.
    I am getting 23.7 volts to the gas valve & 24.2 v at the transformer
    I'm wondering if one of the vacuum switches is acting up.
    HVAC contractor said he checked them but since they have now been here 5 times now I don't have much faith in them.
    I have tried removing the vent fan intake pipe letting the furnace draw basement air thinking that if the vent fan was weak it would help, but that makes no difference.
    The vent intake & exhaust are 5' longer than max recommended but it ran for 15 years with no issue. Thought about up sizing from 2" to 3" but now sure if that would help.
    Will let you know when the problem gets solved.
     
  18. Jan 5, 2011 #18

    paul52446m

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    You said something there that i don't like. Your 24 volt is getting low. Some co. use transformers that just large enough to do the job. A 24 volt
    transformer should start out about 27 volts. This voltage can change by the amount of line volt power you have. Is your furnace on its own circuit?
    Check the incoming power to the furnace. It should be at least 118 volts.
    If it is not then go to you main electrical and test your mains. You are paying for 120 volts and when the voltage drops the amps go up and you pay more for your power. Depending on the power use in your area the voltage can go up and down. So leave a tester in one of your outlets and check it at different times. If you don't have at least 118volts, call your power co. and have them bump it up . That only takes a few min. they can adjust it at you transformer on the pole.
    The lower the line volt power the lower your 24 volt power.
    If your line volt power is up then you might have to get a larger 120/24 volt transformer.
    Transformers have a VA rating on them. Lets say you have a 30VA transformer. To find out how much amperage that will handle you divide the voltage into the VA, so 30Va divided by 24 volts is 1.25 amps.
    Now if your control are drawing 1.75 amps then you 24 volt power will drop too low. Doing service work i have called the power co. many times.
    If you can't get the voltage up or you are drawing more amps then your transformer can handle then you would have to go to a larger VA rated transformer. I have seen people run phone wire for a thermostat and that drops 24 volt power real fast.. Later Paul
     
  19. Jan 6, 2011 #19

    Dtodd

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    Paul,
    Think you might be on to it.
    I see my battery backup on computer had kicked on today although the furnace didn't completely fail.
    I just read 26.7 volts at transformer with vent blower off, dropped to 25.8 with vent blower on and 24.8 with both furnace & vent blower on. Was reading 24 v at gas valve. My house voltage was 120.4 but I was only getting 94.4 volts at the fan limit once the vent fan kicks on, the blower fan did not drop the voltage any further. Getting 120.4 volts back at fan limit as soon as vent fan kicks off - and with the blower fan is still running.
    Vent fan motor casing felt hot so I put a thermometer on it which read 120F with the motor running.
    Beginning to suspect the motor could be the culprit.
    I'll see if I can find an AC amp probe at work so I can get a reading on it.
    Furnace is on isolated 20a circuit with only a light wall style switch between it and the fuse panel (at which I am getting 120.4 volts also). I will try bypassing the switch to see if that effects the voltage drop.
    Thanks again for the help!
    Dave
     
  20. Jan 6, 2011 #20

    paul52446m

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    You might want to go to a larger VA transformer A larger Va will not drop the 24 volt as bad. A24 volt transformer feed with 120 volts usually starts out 27 volts. Can you see a Va rating on your transformer?
    At the furnace check the 24volt going to your thermostat and then the power coming back from the stat. How much drop to you have there?
    Later Paul
     

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