Blower motor not kicking on???

Discussion in 'HVAC Heating & Cooling' started by walds11, Apr 10, 2010.

  1. walds11

    walds11 New Member

    Messages:
    61
    Location:
    Philly, PA
    I had my central AC on for most of the week due to the warm weather. It cooled down a bit, so I turned the heat on my thermostat this morning. The furnace kicks on, but then kicks off after about 30 seconds. I hear a click and then nothing. The blower is not turning on. It did that a few times so far this morning. The pilot is on. What's wrong? It was working fine before I turned on the AC earlier in the week. Help!
  2. walds11

    walds11 New Member

    Messages:
    61
    Location:
    Philly, PA
    Update: I switched thermostat from auto to fan on and it's working. What now?
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    From your description, it appears the fan/limit switch is not working, but there could be other reasons that only proper testing could diagnose.
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,239
    Location:
    Land of Cheese
    On most furnaces made in the last 10-15 years you can remove the front coverto find guidelines for reading the trouble codes from the LEDs on the main circuit board. Since you mentioned pilot light, I am guessing the furnace is older than that.
  5. walds11

    walds11 New Member

    Messages:
    61
    Location:
    Philly, PA
    What's it take to fix the fan/limit switch?

    The furnace is about 18-19 years old. I did not mention a pilot light, I mean't there is a flame down there.

    York Model #PUUGD20N10501A, Serial #EGYM089448.

    It's working now. Go figure.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    If the fan/limit switch is defective, you replace it.
  7. walds11

    walds11 New Member

    Messages:
    61
    Location:
    Philly, PA
    What's that run, both parts and labor?
  8. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The part would be 5 to 10 bucks. Service call..$100. The knowledge and training to find out what is really wrong.....priceless.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    As Jimbo said, the first part of ANY repair is finding out EXACTLY what the problem is, not guessing even when the symptoms give a good indication of what the problem is. Once that is done, then the cost of the repair can usually be approximated. Even then, conditions could be such that accessing the part and installing the new one could be more laborious than anticipated. The starter on my Dodge minivan went bad, so I bought a new one. Normally removing two bolts would take care of the installation, however on this vehicle, they had a strut in front of the bolt so the motor had to be loosened and raised up. The starter went back in the box, used a large pair of Channelock pliers to start the car, drove it to PepBoys, gave them the starter and told them to put it in.
  10. walds11

    walds11 New Member

    Messages:
    61
    Location:
    Philly, PA
    I understand, but wanted to see if I could get a quick idea or quick fix since it is the weekend and no way I am paying for an emergency call.
  11. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego

    We are very sympathetic to that. If either now or going forward you would like to be able to work on this furnace, you need a wiring diagram. Your unit is fairly basic, compared to newer models. You have a pilot light. if the thermostat calls for heat, the pilot tells the gas valve it is ok to open. The burner turns on. Since there would be cold air in the ducts initially, which would just be uncomfortable, the burner runs for a minute or two, and when a temp sensor somewhere in the upper area of the heat exchanger or near the outlet duct, reaches the desired temp and closes its contacts, signaling the blower to turn on. Same thing happens in reverse when the thermostat feels that the room is warm enough....the blower will continue to run for a few minutes, taking advantage of all the residual heat even after the blower turns off. Somewhere in the picture is also a high limit safety switch, door safety switches, and contactors to operate the blower, and a 24 volt transformer for control voltage. That is about the whole picture, and the wiring diagram is fairly simple. You might find that diagram printed on the inside of a cover somewhere. ( Just don't ever run the furnace for long with any covers off...CO backdraft).

    I don't have my York website log on password at home. I will check tomorrow, but I don't think they have old wiring diagrams available on the web.
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