York Furnace - blower motor only sometimes turning on

jeremyp969December 20, 2011

My furnace is about 11 years old and to this point has worked perfectly. This summer the A/C ran fine(I live in VA so it runs a lot) and then when the cold weather came I turned on the heat.

When the thermostat turns on the heat I can hear the furnace start up, the exhaust fan turns on, the gas ignites and it burns for a minute or so but the blower motor never turns on and it shuts off. I then get a code for the limit switch opening...which makes sense because the blower motor doesn't turn on.

If I leave it alone for a while it will cool down after about 5 minutes and try again, and will usually then work correctly. Sometimes it works fine the first try, sometimes it takes 2 or 3.

If on the thermostat I change the fan from "Auto" to "On" the blower motor turns on just fine. I'm a relative novice with HVAC but am learning...Can anyone suggest some diagnostics I can do?

Thanks!

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heatseeker

Okay novice start at the capacitor-good luck- keep being optimistic positiveness is contagious.

    Bookmark   December 21, 2011 at 9:17AM
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harlemhvacguy

You don't list your york mdl# but 11 years old would mean the blower function is controlled in heat by the control board. You most likely have some bad contacts on the heat blower motor relay on control board. Not repairable. you will have to change control board....

    Bookmark   December 21, 2011 at 10:26AM
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heatseeker

Pretty good guess all the way from harlem, How did you determine a bad controller.

    Bookmark   December 21, 2011 at 11:46AM
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harlemhvacguy

because fan runs in fan on(according to him) . ran just fine in a/c according to him the only common thing that doesn't run is low speed fan for heat. low speed fan is turned on by different relay on control board than high speed fan (which works according to poster). can't be cap because cap doesn't work sometimes and not others. can be low on capacitance and overheating motor but it still would not run ok some of the time as stated. best i could do with info given.

    Bookmark   December 21, 2011 at 9:53PM
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jeremyp969

Thanks for the suggestions all....not what I wanted to hear for the bad control board. Is there anything I can do to prove it's a bad control board without buying a new one and trying it?

    Bookmark   December 23, 2011 at 9:44AM
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Eric2612

I have the exact same situation, only my heating system is Gibson.

Was it the control board? If you don't mind my asking, do you remember the approximate cost?

    Bookmark   December 26, 2012 at 1:52PM
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