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Thread: AC condensor fan motor

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    Methodical is offline New Member
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    AC condensor fan motor

    Hello all. New to the forum and need some help with a AC condensor fan issue.

    Today I came home and heard some weird noise coming from the side of the house and when I checked I noticed the AC condensor fan was not spinning but everything else sounded as if it was working. It was not that hot at the fan plus when I went in the house to turn the unit off it was pretty cool in the house. So it appears to maybe just happened or at least stop running for a short period of time. The unit was working perfectly fine this morning before I left for work.

    What should I do to determine if the fan is the only problem? If it's the motor are there any special steps needed to be taken to replace the motor? It doesn't look to be too daunting of a task plus I am mechanically inclined. HELP!!!

    Note: I did a search and noticed that some responses stated to maybe replace the capacitor along with the motor. Should the capacitor be replaced also.


    Spec info: Comfortmaker condensor (just over 10yrs old) ; Model No. K55HXPSS7299 Motor PN: HQ1082641EM (1.3 amp, 208-230v, rpm 1075); Maker of motor IEmerson.

    I did some research and got this info. The unit is a Permanent split capacitor (K), stator lamination is 5.5" (55), motor includes an integral thermal protector of the automatic reset type and motor protector combination (HX) that is recognized for locked-rotor and no load no-air-over running-heating protection. Don't know what all this really means but some added info that may help.


    I appreciate any help.
    Last edited by Methodical; 08-04-2008 at 06:32 PM.

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    HayZee518's Avatar
    HayZee518 is offline Deity
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    the motor is internally protected against overloads by an integral thermal protector. this is a thermal overload device that is embedded within the windings. stator laminations means how the iron punchings are arranged that make up the motor stator, this is what the windings are wound upon. the motor is of the induction type. its rotor is one piece made up of iron punchings laminated together with aluminum shorting bars on each end. locked rotor means the current that the motor is exposed to when the rotor is not turning as in frozen bearings. for troubleshooting a motor you'll need an analog meter and a clamp around ammeter. use the meter on its highest voltage adjustment and read the voltage on the line side of its contactor. when its running or trying to run use the ammeter around one conductor to direct read its current. compare that to its nameplate reading. the control circuit is probably 24 volt, so all the coils in the motor circuit will be running at 24 volts. there may be a control fuse on the secondary of the control transformer, this steps down the 120 volt to 24 volt for control.

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    Methodical is offline New Member
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    update

    Update: I turned the motor a little and turned the AC on and the fan worked all day (8/5) but stopped working again tonight (8/5).

    How does the capacitor affect the fan motors operation? I'm thinking that maybe the capacitor is acting up.

    Also, would it help to put oil in the motor? If so what kind of oil?

    I'm leaning towards just replacing the motor. Where is the capacitor located? There's a box near the condensor that has markings that say "not a fuse box" if I recall correctly. Is this the location of the capacitor?

    Does anyone have a link that shows how the system works so that I can better understand.

    Again thanks
    Last edited by Methodical; 08-06-2008 at 01:03 AM.

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    HayZee518's Avatar
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    a permanent split phase motor has a capacitor mounted outside the motor in an oval cylindrical metal housing with a cap on it. a capacitor is used to offset one winding to get the magnetic field to lag the starting current. a motor functions - the rotor is trying to chase the revolving magnetic field - playing a sort of "catch-up." there are two types of capacitor motors. one is capacitor start, the other is capacitor run. in the case of capacitor start there is a centrifugal start switch underneath one end bell of the motor. a system of flyballs spin outwards when the motor is up to speed. it opens a contact in series with the start capacitor. capacitor run, the cap is in the circuit all the time. the thing you noticed "not a fuse box" may be the motor overcurrent relay box. it is a current sensitive relay that cuts out the motor if an overload is present. if there are motor lubrication holes, look for yellow or red plastic caps on each end bell, apply a light machine oil. don't use wd-40 - it has a solvent -
    Last edited by HayZee518; 08-06-2008 at 05:30 AM.

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    Methodical is offline New Member
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    Cool. Thanks for the info. Will be hard at work starting this evening

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    Methodical is offline New Member
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    Another update: Yesterday I open up the outside unit and checked the fan. The fan spins freely with no noticable wobble. I did not have a analog meter to test the capacitor. But I believe it's still good because the compressor kicks on just the fan is not spinning (or it barely spins). I determined that it is a dual capacitor and is rated as follows: 35+3/440v.

    Now I ordered (no one locally seems to have this motor or if they do have they are not willing to sell to me - only contractors) the motor that Emerson crossreference to the OEM part number but the new motor is to be used with a single capacitor rated at 5mfd/370v but the sytem currently runs with a dual capacitor.

    What do I do now?

    Will I have to get another smaller capacitor just for the compressor or can I use the dual capacitor in the unit now?

    If I use the existing dual capacitor how will that affect the new motor?


    Oh and I determined that the box outside the house is a breaker. I just pulled the jumper out.

    Please help.

    Thanks

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    HayZee518's Avatar
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    if the oem company sent you a single cap motor as a replacement use it! you don't have to "re-invent the wheel" so to speak. you don't use a meter for testing the capacitor. you use a well insulated screwdriver. use this procedure and don't vary from it. with power on start the unit, then shut it off. remove ALL power to the unit. MAKE SURE YOU DON'T HAVE ANY POWER GOING TO THE UNIT! IF YOU DON'T YOU KIN GET KILLED! Remove the metal cap on the capacitor and short out from the common terminal to either or both other terminals. If the capacitor is good you're gonna get a nice fat spark! If you get a spark on both terminals to the common terminal the cap is assumed to be good. no spark the cap is shot.

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    Your condensing unit has two capacitors because both the fan motor and the compressor motor are PSC motors.

    In your case they are using a 35/3 ufd dual capacitor. When facing the label side of the capacitor the terminal on the left side is a 35ufd capacitor for the compressor and the terminal on the right side is a 3mfd cap for the fan motor. The center terminal is common for both capacitors.

    You can use a universal replacement motor.

    I am attaching an illustration on universal replacement motors and capacitors.

    When selecting a universal motor you must make sure the shaft is the same diameter and the same length or longer (you can cut some off later if necessary)

    You must have the correct rotation: check the data plate on your old motor for rotations..CW=clockwise CCW=counter clockwise REV=reversible
    (most universal replacement motors are reversible.)

    Check the horsepower..this is critical because if you new motor is undersized it will overheat from mechanical load. If its oversized it will overheat from electrical load.

    Check the rated RPM on the old motor. RPM is critical because the fan blades are HP rated to a specified RPM. If your new motor is too fast it will overload mechanically and if too slow it will overload electrically. (Most universal replacement motors are multi-speed motors. During installation you select the proper wire to line 1 on the contactor to proved the required RPM. The other RPM wires are then cut short and capped off.

    The exact capacitance requirement varies greatly from one size of motor to another but it may also vary from one motor manufacturer to another. It is always best policy to install a new capacitor matched to your new motor.
    Attached Thumbnails Attached Thumbnails AC condensor fan motor-ac-run-capacitors.jpg   AC condensor fan motor-plumbing-152.jpg   AC condensor fan motor-univwersal-fan-motor.jpg  

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    Methodical is offline New Member
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    Thanks for the info. I will report back soon.

    Update: I purchased a 5mfd/370 capacitor and connected the brown wire from the motor to one terminal and a jumper wire between the existing capacitor and the new capacitor. The fan kicked on and the AC is working fine now. So the motor side of the capacitor was bad.

    Additional ?s:

    Although the motor requires a 3mfd/370v capacitor will the 5fmd/370v capacitor damage the motor?

    Should I purchase a new capacitor for the compressor since the motor side of the capacitor is bad?

    Thanks everyone for the help and insight. Much obliged.
    Last edited by Methodical; 08-07-2008 at 07:43 PM. Reason: to provide update on AC

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    Methodical is offline New Member
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    Fan stopped again

    Another update: Well the motor stopped again this morning. As long as its running its fine but when it stops it does not come back on. What I noticed is when I initially spun the fan (thru the top vents) with a screw driver it would not spin as easy - turned ac on and nothing. But after a couple minutes of messing with it, it spun pretty easily (could get one full turn) - turned the AC on and now the fan is on again. So to me it seems to be the motor is on its way out so I will change the motor and go from there. Sigh.

    Thanks for your ears.

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