York Stellar Plus won’t ignite

Discussion in 'HVAC' started by rodge, Nov 1, 2008.

  1. Nov 1, 2008 #1

    rodge

    rodge

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    Natural gas furnace, 12 years old, small, only heats 2 rooms,
    Sticker says model # M3UF024SA for cooling, P2UDD06N03B01D for furnace, can’t find it anywhere.
    Situation:
    When heat is switched on motor starts running, pressure switch (the one on the right with 2 wires) closes (multimeter reads 0V), but hot surface igniter won’t ignite.
    Disconnected the igniter and there is no voltage coming in to igniter contacts.
    Igniter itself looks OK, not broken, a little charred, ordered new one just in case.
    No diagnostic LED here, like our other unit York Diamond 80 has.
    Question:
    What could be the problem, what can I test further myself ?

    photo with upper part door open:
    P1020401.jpg
     
  2. Nov 1, 2008 #2

    kok328

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    For a 12yr old unit, this one looks really clean.
    After the pressure switch is made, the flame sensor/ignitor should be energized.
    What is the second pressure switch hooked to?
    It appears this is not a standing pilot system but, rather an electronic ignition system. Does the ignitor glow red/orange after the pressure switch is made? Does the system just shut down after ignition failure?
     
  3. Nov 1, 2008 #3

    rodge

    rodge

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    Ignator looks like this
    http://www.theignitorstore.com/thumbnail/product/64297/640/480

    If electronic means no pilot light, then it's electronic.
    Normally it should glow, but does nothing.
    Somethere I read(not about my model), that there should be 115 v coming to ignator. I disconnected the plug and tested and it reads 0.
    So the problem between pressure switch and ignator, but what?
    The other pressure switch has 3 contacts I dont know what it is for.
    I saw video on youtube
    [ame]http://www.youtube.com/watch?v=P3-Ki-eEWo8&feature=related[/ame]
    how to test pressure switch. they talk about 2 contacts, that's what I have on the right side and it closes(reads 0).
     
  4. Nov 1, 2008 #4

    kok328

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    A really stupid question but, are the gas valves on?
    I can see for sure but, it appears that the pressure switch on the right is tied to the pressure switch on the left, at least on the clear tubing. The pressure switch on the right is tubed to the inducer motor. I guess we need to see whats going on with the pressure switch on the right. Where do these 3 wires go? Is the ignitor connected to the circuit board?
     
  5. Nov 1, 2008 #5

    rodge

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    Gas is on; blue switch inside and red outside.
    Pressure switches not connected with each other.
    LEFT one(with 3 wires) connected by tube to inducer motor.
    Tube from the RIGHT switch(with 2 wires) splits in 2: to top gas chamber and to gas valve(with blue gas switch).
    What does it mean and how to test them?

    Will check that pipes for inducer and exhaust are clean, they are not meshed on outside.
    Could it be the reason for not lighting up?
     
  6. Nov 2, 2008 #6

    kok328

    kok328

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    Sorry, I typed it all wrong. It appears that the pressure switch on the left is tubed to the inducer motor and the other pressure switch on the right. At this point (and I'm not sure why) it appears that York has on pressure switch for the ignitor and one pressure switch for the gas valve?
    If the inducer motor is running and maintaining rpm to the satisfaction of the pressure switch then blockage in the exhaust would be irrelevant. I'm sure you already did but, start looking for loose connections, check your ignitor for continuity. If you see any relays, give them a sharp tap while the unit is still in the startup cycle.
     
  7. Nov 2, 2008 #7

    kok328

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    Another thought, check for any reset buttons and check for continuity on any limit switches.
     
  8. Nov 2, 2008 #8

    rodge

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    There is what I suspect is a limit switch, round with 3 tabs, has too many wires connected, how to check it ?
    Checked pipes – clean.
    This unit is heating/cooling and cooling is fine, I had to say it earlier - might mean less tests.
    Found the control board in lower compartment with diagnostic LED.
    Hoped to see it blinking but it’s off all the time, not a blink.

    Situation remains:
    On call for heat, inducer motor starts and runs and nothing else happens. I let it run for 5 min – nothing, runs until switched off by furnace switch.
    My goal it to find the part needing replacement( pressure switch , control board, ???).
    I will risk replacing myself anything under hundred bucks.

    Right pressure switch has NC and C terminals wired.
    Left pressure switch that’s tubed to inducer has NC, NO and C terminals wired.
    Tubes clean, no cracks.
    How to test their electricals?
    What would be the sing of bad control board?
     
  9. Nov 3, 2008 #9

    kok328

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    test for continuity on the limit switches and the same for the pressure switches but, test them when the inducer motor is running.
    As far as the control board, when all else fails, replace the board but, I don't think we're at that point just yet. I have a feeling it's something really stupid and we'll both be kicking ourselves in the butt when it comes to light.
     
  10. Nov 3, 2008 #10

    rodge

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    sure feels like something stupid (disconnected wire), before the pressure switches.
    Found troubleshotting manual for control boardhttp://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/Cat_06_pg0278_281.pdf
    Going through chart 1(page 2)
    with inducer running there is 25v between C and R on tranformer,
    but there is 0V between TR and TH on control board.

    Board has no power! Doesn't mean the board is bad.

    here is from left to right board, transformer, limit switch.
    FFF.jpg

    Does something look strange?
     
  11. Nov 3, 2008 #11

    kok328

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    Pic 1 is the ignition control module, is there a green printed circuit board present?
    Pic 2 is the terminal block for the T-stat, I can't see the transformer but, on a York anything goes. I think the transformer and T-stat terminal block are one unit. When calling for heat, you should have 24VAC across R&C, C&W, and possibly C&G, check these. If no power across R&C then either you don't have primary power or the transformer is bad. No power across C&W, the T-stat is bad (keeping in mind this York thing, could still be the transformer w/no power to W).
    Pic 3 is the tempature limit switch set at a low of 85 and a high of 165. You should see volatge from chassis ground to line and load if the switch hasn't cut out. I believe this controls the fan blower motor.
    According to the troubleshooting guide, you have a bad 24V limit switch bad. I think (verify), the limit switch is 120VAC. Look for a little silver can like button about the size of six dimes stacked together, with two wire leads coming off it. Most likely located in or around the burn box.
    Also in the troubleshooting guide in the lower left corner of page one, there is a diagram that show a 24V limit switch that cuts power to terminal TH of the control module. Find this switch and test it for continuity across the leads.
    What are the results of the ignition control module test from the troubleshooting guide?

    At this point the only thing we know for sure is that I have no idea of what I'm talking about.

    P.S.- You didn't hear this from me but, as long as your monitoring the burn box and only doing this as a temporary test, you can jumper out the limit switch and see what other problems might exists.
    And man do I mean temporary, like just once to see if the system fires. Be absolutely prepare to pull the jumper off if the burn box is malfunctioning or you'll burn down your house. It could be that this switch just died or there is truly a problem with excessive temps or flame rollout in the burn box.
     
  12. Nov 4, 2008 #12

    rodge

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    You were right on!
    The switch! First I didn’t see anything in the burn chamber, then looked in our main unit York Diamond 80 and saw the cylinder switch!
    In this small broken unit same wires just seem to go to the ceiling of the burn chamber, but there was a switch there and looks bad.
    Sure there is no 120V there, will replace it.
    [​IMG]
    [​IMG]

    Thank you soo much, but please stick around. I’m not that brave to jump the switch and see what else is wrong. It very well might be.

    Replaced pix in previous posts with links as to not to use much space and keep the thread open( and someone else might find it useful).
    You right that on pic 2 in the previous post is terminal block for the T-stat. It's glued to the transformer and together they look like this: P1020418.jpg
     
  13. Nov 4, 2008 #13

    kok328

    kok328

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    Sorry, the limit switch shown is not what I'm used to seeing but, is none the less the correct item in which we set out to find.
    Test this switch for continuity and this will tell us if it is good or bad.
    The switch should yield continuity if it is good.
     
  14. Nov 4, 2008 #14

    rodge

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    the switch/fuse has no continuity, needs to be replaced.
    I searched for exact same one, found info but no place to buy it.
    It opens at 152 degrees C or 306 F.
    I think it was not supposed to be there. Is is held by 1 screw, but there are 2 screw holes in the place I found it; looks like cylinder switch was there originally.
    I will replace it with cylinderhttp://www.heatingandcoolingwarehouse.com/v/vspfiles/photos/02527747016-2T.jpg
    It's better as it has reset button.
    Only concern - the cylinder opens at 320 F.
    What do you think?
     
  15. Nov 4, 2008 #15

    kok328

    kok328

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    replacing a 306F switch w/a 320F switch, I don't think I could sleep at night. It seems that the orignal switch has been replaced (probably the one I described) and the OEM F rating is long gone. I know, your saying heck, it's only 14F difference but, if the original was say 290F, then we could have a problem, now we're off by 30F, which more than double the original offset.
    If you can, try to find the proper switch (keep in mind that someone replaced the original w/a close enough switch). If the F rating of the replacement switch is too low, you'll just burn them up. If the F rating is too high, you could risk burning down your house. Try googling the unit or call a local H&C company or a York dealer and see if they can determine the proper F rating for a replacement switch. Once you know the proper F rating for the switch, try Graingers.com they seem to have just about everything under the sun and don't require a contractors license, account or problem finding them.
     
  16. Nov 8, 2008 #16

    kok328

    kok328

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    It appears that Rodge either didn't like my last answer, got his heat working, blew himself up or all of the above.
     
  17. Nov 9, 2008 #17

    Square Eye

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    Maybe he called a local pro?
     
  18. Nov 9, 2008 #18

    kok328

    kok328

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    Yea, that would fall under the "got his heat working" catagorey. Lord knows, I wasn't getting him anywhere.
     
  19. Nov 9, 2008 #19

    rodge

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    You helped a lot and it's much appreciated , especially as problem still stands.
    I was just distracted by other things.

    Bought 320F switch. Using it temporary to fix this unit. If fixed, I’ll find the right one for perm and keep 320F as a spare for our main unit.
    The broken unit heats/cools sun room on main floor and den in the basement and both rooms are part of open floor plan and served well(though not directly) by the main unit.
    Fixing this small unit not critical now, but to have it ready for colder weather and in case the main unit breaks is very important.
    I really want to fix it, not replace, because the cooling half is working great.
    And the pro will sure insist on replacing it. There is no info on this model anywhere anymore.
    Anyway, putting the new switch in hasn’t change anything. Will do some poking around today and post results.
    Please check this thread
     
  20. Nov 9, 2008 #20

    rodge

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    Some history:
    At the end of last heating season this unit would ignite burners and after a short while the flame would go out.
    I left it at that till new season, and when decided to take a look – it won’t ignite at all.
    With the help from kok328 found bad high limit switch.
    Now, seeing the high limit switch in really deteriorated state it explains for me last season problem – switch opened at lower temps and finally opened for good.

    But replacing the switch, did nothing to fix other(new this season) problem: unit doesn’t even try to ignite.
    Ignition control board LED should blink once at the beginning indicating ready – it doesn’t.
    Pressure switch is open.
    I disconnected pressure switch tube from inducer and sucked in for a moment with power on and heard the switch click and control board LED blinked!
    Do I have bad inducer?
    It makes noise, warms to the touch and blows air out white PVC pipe outside.
    Tube to the switch is not damaged. Some other tubes connected to it look greasy on inside. Here is picture. [​IMG]
     

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