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Ducane central unit issue

Hope someone can help me out. Ive got a two ton residential Ducane central air unit, about ten years old give or take, and the condenser fan went. I replaced the fan, worked great, then new fan would shut down for a bit while compressor continued to run, then would come back on. I then replaced the capacitor, same thing. Then compressor popped off the hi pressure valve(if its got one)..and now ive got an empty system, and no cold air...any ideas?


  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    You probably either don't have the right fan motor or fan blade or a combination of both. The fan motor may be overloaded and tripping on thermal.
    JUGHNE Member Posts: 10,801
    Everything Harvey said......motor and blade must match the original.

    Also must run in the right direction, If rotation is wrong it may seem to be doing its job but not moving enough air.
    Also how clean is the coil for air to be sucked thru it. Best to back wash the coil with water in reverse direction of air flow.
    Power must be shut off at AC disconnect!!.....not just T-stat.

    Do you know if gas charge actually was released? It would have been an oily mess somewhere. There may be a high pressure switch which would shut compressor down until pressure subsided.
    EBEBRATT-Ed Member Posts: 13,834
    What @Harvey Ramer & @JUGHNE said.

    I ran into this years ago. If you can't get an exact replacement motor make sure that the replacement motor has at least the same or higher amp draw as the motor it replaced.

    You can't trust ANY OEM to rate their motors correctly, they cheat. Foud this out the hard way.

    As Harvey said and I agree it sounds like the motor is tripping thermal overload.

    If you install a motor check the amp draw with it running. Be sure to have all the covers in place
  • newagedawn
    newagedawn Member Posts: 586
    could be the fan runs off a pressure switch, and id bet it does, it was probably runing not runing when you lost refrigerant, if all the refrigerant leaked out , you have a leak somewhere, i like to check the Schroeder first they are infamous for leaking, a way to check is fill the system to 100 psi with nitrogen, make sure the system is indeed empty of refrigerant and go around with soapy water
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • Big Ed_4
    Big Ed_4 Member Posts: 2,377
    Hmmm ....was the fan wired directly to the contactor and capacitor or was there an control in-between ? Like an low ambient switch ..
    I have enough experience to know , that I dont know it all
  • unclejohn
    unclejohn Member Posts: 1,833
    Did you hear the pop off of the valve. It does not have a relief to atmosphere valve. It may have a internal relief that gets real loud and blows hot gas onto the motor winding sensor which will keep the compressor off for 3 to 5 hours until it cools down.