How to troubleshoot this ac?

Discussion in 'HVAC' started by farmerjohn1324, Feb 23, 2018.

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  1. Mar 9, 2018 #21

    kok328

    kok328

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    Graingers can hook you up.
    You’ll need the rating or just take the old one with you and they might test it for you too.
     
  2. Mar 11, 2018 #22

    farmerjohn1324

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    Where do I buy a multimeter with long terminals like that? The terminals on the ones from HD/Lowe's are so short, I can't even trust that they're working in this application.
     
  3. Mar 11, 2018 #23

    slownsteady

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    Is the motor free to spin? Nothing fell in or is resting against a moving part? Just a couple of simple things to check.:rolleyes:
     
  4. Mar 11, 2018 #24

    farmerjohn1324

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    It spun freely. My multimeter told me zero for the capacitor, so I'm guessing that's it unless my meter is not good enough.

    Do you know where I can get one with long terminals?
     
  5. Mar 11, 2018 #25

    kok328

    kok328

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    Zero what? Chances are the meter you have is not capable of reading a capacitor.
    Graingers can hook you up with the appropriate meter too.
    but at this point far cheaper to gamble on a new capacitor.
     
  6. Mar 19, 2018 #26

    farmerjohn1324

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    Replaced the capacitor. Still doesn't work.

    I noticed something I didn't notice before. The blower motor can be spun by hand only when the power is off. As soon as I try to send power to the motor, it locks up and can't be spun.

    Does this mean I 100% need a new motor? Where do I find one?

    And why would all this have started when I changed the filter? I replaced an old, dirty one with a brand new one of the same size and brand.
     
  7. Mar 20, 2018 #27

    farmerjohn1324

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  8. Mar 20, 2018 #28

    kok328

    kok328

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    Yes the motor is toast and it had nothing to do with the filter change it was purely coincidental.
    No, you do not need a puller to change the motor.
    You managed to get the blower and housing out of the unit, that is good.
    Now you need to loosen the set screw on the hub of the blower wheel with a long handled allen wrench.
    Then remove the 3 motor frame bolts from the housing.
    From there you can separate the motor from the wheel and housing and will be able to see the "nameplate" info on the motor to order a new one.
    Again, Graingers has your back. The only reason I recommend them is that they will sell to you without a contractor's license, can locate just about anything and is a common name when I don't know what suppliers are around your locale.
     
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  9. Mar 20, 2018 #29

    farmerjohn1324

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    Thank you.

    I pulled this screw out with an adjustable wrench. Is this the set screw you're talking about? I took out the 3 motor frame bolts also.

    I still can't get the motor detached from the wheel. There's a piece I can turn independently of the wheel (red arrow in picture) if I hold the wheel still, but this doesn't cause the motor to come loose, even after turning it with a wrench for several minutes in either direction.
     

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  10. Mar 21, 2018 #30

    farmerjohn1324

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    Doing some research. Pretty sure I need a hub puller for this.
     
  11. Mar 21, 2018 #31

    lou-in-usa

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    Pull the capacitor out, it's usually strapped to the blower housing. Look at how many microfarads and volts it's rated at or take it to an electronics store. Or look on eBay, just make sure you get a replacement with the same values. Thief melting frost on the a coil could have damaged the capacitor, rusted the shaft at the bearing on the motor and caused it to seize, or otherwise damage the blower.

    Before you put it all back together, consider doing a thorough cleaning of the a coil. If you ran it any length of time without a filter, or that was a normal practice from a previous owner, then putting a filter in now, won't help the fact that you're coil fins are clogged with garbage and causing a lack of airflow and therefore causing your coil to freeze up.
     
  12. Mar 21, 2018 #32

    farmerjohn1324

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    Okay.

    I already tried changing the capacitor. Didn't help.

    How do I clean the evaporator coils? I had planned to clean the blower wheel also if I can get it off.
     
  13. Mar 21, 2018 #33

    lou-in-usa

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    If your blower is not spinning when you switch the thermostat to "Fan On", then that is your first priority, because cleaning the coils won't make the blower spin! If you know how to use a voltmeter, you can see if you have line voltage (~120 VAC), across the wires connecting to the fan motor, but you have to know which wires you should be seeing voltage on, and that depends on you being able to understand a wiring diagram that may be inside your cabinet, or maybe one you can find a schematic online; blower motors can be single or multi-speed, and you have to know what color wire you should expect voltage on. Maybe someone else here can help with that. Also note that induction motors almost never burn-up, and you if your motor did, you'd probably detect the acrid smell of burned/melted wiring insulation. What typically happens, is the bearings wear to the point where the rotor becomes off-center enough that the magnetic phasing that would normally start the motor spinning, can't because it's uneven. Another thing, if your squirrel-cage is so rusted onto the motor shaft that you need a puller to remove it, I'd bet the bearing part of the shaft is also rusted and ruined the bearings, and it doesn't take much for the rotor to be too far off center to prevent the motor from starting.

    If you have no voltage to the motor, and you don't hear a relay click when you switch on the fan, then I'd bet your water, got to the fan relay or some other electronic component, in which case you should call a professional.
     
  14. Mar 22, 2018 #34

    kok328

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    Yes, that is the set screw I was referring to. Try a little liquid penetrating oil on the shaft and hub. If you've loosened everything up, you should be able to use a hammer and drive the shaft out of the hub. Be careful not to distort the yolk on the fan hub. I've never had to use a puller on these before.
     
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  15. Mar 26, 2018 #35

    farmerjohn1324

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    Does anyone know how to hook these wires up?

    7 wires total. The ground is obvious, as are the 2 for the capacitor.

    That leaves me with a black, blue, red, and white. I believe that the black, blue, and red are all hot wires, and the white is a neutral.

    From the wiring diagram, it looks like I might be supposed to pick one of the hot wires, and cap the other two? What do I connect the "chosen" hot wire to? I believe this fan is only one speed, so which do I pick?
     

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  16. Mar 27, 2018 #36

    farmerjohn1324

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    Okay I Googled it.

    The white goes to neutral, obviously.

    And I'm supposed to pick ONE of the hot wires, and cap the rest. Generally, I pick the highest speed.

    And it only makes sense that the previous wiring had a yellow neutral and blue hot.

    Not really sure where to attach the ground wire to, but maybe it will become obvious when I get it back in.
     
  17. Mar 28, 2018 #37

    farmerjohn1324

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    I have a few questions about the disconnects.

    Can I crimp them with these wire cutters, or do I need a special crimping tool? The wires pictured are from the old motor. The old motor had more plastic insulation than the new disconnects that I bought. Do I need to buy additional insulation to attach the these new female disconnects?

    Also, I can't quite figure out how to reattach the neutral (yellow) wire to the unit. It had two yellow wires (one from motor, one from elsewhere) going to a connector within the unit. (Pic attached of connection before it was disassembled). Now I'm looking at all these same parts, and can't figure out how to connect two female disconnects to the same terminal.
     

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  18. Apr 14, 2018 #38

    farmerjohn1324

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    Is there any way to know which of the secondary voltage wires from the old transformer (red or brown) is the Common "C" wire, and which is the "R" wire?

    The new transformer does not come with wires attached, but labels terminals "R" and "C."

    If there's any clue, the two terminals on the circuit panel they were connected to are labeled "C" and "T" but I don't want to assume anything and guess wrong. The brown was connected to the "C" and the red to "T."
     

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  19. Apr 14, 2018 #39

    farmerjohn1324

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    What is going on here? I needed 18 gauge wire for the 24V transformer wires. I bought 18-2 wire, sold as "thermostat wire" and cut off the sheathing. The 18 gauge wires that were inside (red in the picture) are WAY smaller than the 18 gauge wires that I see elsewhere. The red and white thermostat wire fit in the 22 gauge space in my wire cutters.
     

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  20. Apr 15, 2018 #40

    kok328

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    Yes, you can crimp with the wire cutters.
    No, you don't need different connectors but, a better brand would have been nice.
    To connect two females to one male, you need the adapter piece that was under the yellow wires.
     

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