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Need to replace HVAC motor

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  • Need to replace HVAC motor

    Is this the type of component that can be bought "locally"? One of our AC units was making a lot of noise and so it was switched off. When I got home and checked it out I found the fan to be very stiff. I could turn it by hand but I could definitely not spin it. When the thermostat is switched to COOL the fan does not run and the unit gets HOT! So I have decided that the problem is with the motor and would like to replace it. It doesn't seem like a tricky job so, at this point, I am reluctant to shell out extra money to have someone replace the fan. The tricky part could be getting the part. I could order it online and have it delivered if necessary but if I can get it locally for a couple of bucks more I don't mind supporting local business.

    From the motor housing:
    1PH A.O. <--- don't know what this means but I understand all the other numbers.

    The motor has a 5" diameter and is attached to the housing via 4 bolts in a square pattern with a diagonal of 4 5/8"

    We have 3 units in total and the one that is busted is the one that we don't need to really use as much unless we have guests (which we do as of yesterday).

    The capacitor is 5MFD 370VAC. (is that millifarads by the way?)

    Cheers, Max

    EDIT: by the way, when I say locally I understand that depends on where local is. I should have said can you typically buy this sort of item locally. Local for me is MA by the way.

  • #2
    Hey Max!

    Yes that part should be EASILY obtainable from any HVAC Supplier or a shop that specializes in electric motor rewinding / rebuilding / or new equipment... Check your local phone directory for one of those shops and take the old one with you so they can easily match up what you have to the equivalent or even something better (more efficient.. better power factor etc.) unless of course you go to a motor shop and its cheaper to have it re-built rather than replaced... Check out all your options.

    Oh Ya.. " MfD" on a capacitor stands for Microfarads.. not Millifarads

    Good luck!


    • #3
      Thanks Rewired. I thought milli sounded a little on the large side.

      I did another test just now. My earlier report of "I could definitely not spin it" is not 100% true. It can spin but only for about a second after I let it go. When I had my wife switch the thermo to COOL again the fan moved a tiny little bit (only a couple of degrees) and the outside of the unit got HOT real quick. I guess that's why you need a fan. Am I correct in saying that if the unit is getting hot, the fan SHOULD be spinning? That makes sense but since I don't know HVAC that well I can't be 100%.

      Cheers, Max


      • #4
        That appears to be a very common condenser fan motor but before you begin looking for a replacement there is some additional information you should look for.

        Name of Manufacturer

        Model Number

        Frame Number (The frame number refers to a precise set of industry standards that define the diameter, length, type of mount and other dimensional specifications. (Those dimensions will remain constant regardless of what company made the motor.)

        Rotation- defines the direction of rotation when facing the shaft end of the motor. You motor should have an index on the data plate that says either CW or CCW for Clockwise or Counter-clockwise rotation. (Some motors are listed as REV for reversible but that is very unlikely on a condenser fan motor.)

        The capacitor you have is a 5MFD which means Micro-Farad, it could also be indicted as 5uF. (The small letter u indicates the latin prefix Micro) Whenever you replace a motor it is best to replace the capacitor at the same time.

        Check the SHAFT Diameter and length. Shaft diameter and lenght is critical because the fan blades will mount directly on the shaft and their position in reference to any sheet metal shrouds in the condensing unit are critical.

        From the type of mount you describe it sounds like it is bolting directly to the mount plate by the motor housing bolts. Sometimes it is necessary to remove the bolts one at a time and reverse them end for end through the motor to get the excess end of the bolt on the mount end. It is a very simple process of removing a bolt and sliding it through the motor housing from the opposite end and tighening it in place again, then move to the next bolt.

        You should be able to find a replacement motor at any local HVAC supply house, or Mill Supply. (Graingers and Johnstone are a couple national suppliers that are quite common in massachusetts.)

        The motors are interchangeable between different manufacturers as long as all the specifictaions are the same but I would hesitate to buy a generic name. Try to find one of the well established trade names, GE, Marathon, Dayton Electric etc.

        It is always a good practice to replace the capacitor when changing a motor to insure the capacitor is matched to the new motor.

        When installing the new motor check the position of the blades on the shaft carefully to insure the blades are properly aligned in the fan shroud. MAKE SURE THE SET SCREW ON THE FAN MOUNT IS REALLY TIGHT.


        • #5
          I'm looking forward to when you get time to write a detailed response LP. Serious, man, great response and I am MOST appreciative.

          The info I gave before was just the basics but I do have all the other info noted as well. The manufacturer is / was Magnetek Universal Electric. I have the serial number and model number too. One other piece of info that I found interesting but don't understand is this:

          #20 non-det oil every 6 mo. max amb 40o C.

          So I have to do "something" with some oil every 6 months and the maximum ambient temp should be 40 degerees C (or 104). Heck, Boston is THAT hot. Still, I don't know what the "something" is.

          Thanks, Max


          • #6
            #20 non-det oil every 6 mo. max amb 40o C.

            That is indicating that the motor bearings should be oiled every 6 months with SAE 20 weight Non-Detergent Oil and the motor is designed to operate in a maximum ambient temperature of 40 deg.C.

            As you pointed out, the 40DegC converts to 105degF.

            Having formerly lived in the W.Springfield, Holyoke, Chicoppee area I am quite familiar with summers in Massachusetts. It is possible to get the occassional 100 to 105degF day, but for the most part typical summer ambient temps would be closer to the high 90's so that motor is fine.

            Allow me to offer you a little tip here as well...

            When you get your new motor get some stainless steel non-insulated SPADE connectors to attach to the wires on your new motor to make the electrical connections. The stainless steel connectors cost a few pennies more, but you dont have to worry about corroded connections causing voltage losses.


            • #7
              In the electronics industry, the prefix small m usually is milli, large M is mega. Capacitors usually use u for micro.'

              In the electric motor trade, you usually see Large M used for Micro...farads, although they sometimes use UF.


              • #8
       shows the label from the old motor.


                • #9
                  Anybody got any (more) tips on picking this up? I just came back from my local Johnstone's and they were unable to help me based on the label (img link above). I'm sure that I can just pop in a direct replacement even if it's not exactly the same specifications but I do know that some specs must be an exact match such as the bolt pattern. I'll try some online places and see what mileage I get there.

                  Edit: Contacted Grainger and they said the same as Johnstone, that is they can't help. I think the problem is the lack of information on the motor. Johnstone's suggested contacting the manufacturer of the AC unit and see what they say.


                  • #10
                    Here's the label from the unit.



                    • #11
                      w.w. grainger is a good source for replacement motors.


                      • #12
                        Thanks, HayZee. Any idea what information I can give them? I've contacted both Johnstone and Grainger and given them all the info I have (links above) but no success yet.


                        • #13
                          Forget the info there take the motor in with you and Ill bet they will match it for you. Both of them Grainger or johnson


                          My mistakes dont define me they inform me.
                          My mistakes dont define me they inform me.


                          • #14
                            I'll try that Imeduc. Both of them are close enough to me and I have the motor off anyway.

                            Thanks, Max


                            • #15
                              Find a local electric motor co or a/c supplier - hate to say it because I own a A/C co., but most of your local hvac distributors will have and sell you one too.

                              Have you changed your filter this month?

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