Replaced capacitor but my furnace fan started making a humming sound today, so I pulled the front panels off. When I looked inside there was a fair amount of dust and stuff so I took a shop vac to it. When I got to the squirrel cage I noticed that the motor was hot & smell something burning. I can turn it by hand, but when the blower is supposed to come on, it just hums. If I rotate the fan by hand it will start but it's noisy and not up to speed. I'm guessing it needs a motor, but could it be something else? If it is the motor, where can I find one? It's an old GE 1/3 hp, 4.8 amp, 115v, dual rotation shaft. Any ideas where to look for a motor?
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Tom P's answer is generally correct: The motor start capacitor is usually not the problem. However, in some cases, particularly on older furnaces, where there were capacitors of certain make and production run will prematurely fail. This happened in March on a mobile home HVAC unit where both the blower fan and condenser fan motor capacitors failed open circuit. Both caps were of the same Mfg, and production lot.
Here is a suggestion (for you or an electrically inclined friend): Locate a substitute motor capacitor having similar Mfd (or MF) and Voltage ratings. Remove power from the unit. Reach into the blower squirrel cage and spin it to verify that the shaft is not frozen. Pull the wires from the existing capacitor noting color and location. Connect the wires to the substitute capacitor and secure it place. Apply power and turn on the blower. A no start? Motor replacement time.
Replace the capacitor inside the control panel on the outside unit. The top of the capacitor may be puffed up. The fan motor may also be going bad. Change the capacitor first. It will have to be changed anyway if the motor is bad.
Hello, if the compressor is running then it is either a bad capacitor or bad fan motor, an easy way. To check is try to spin the fan blade with a thin object, if this gets the motor going the capacitor is bad if not the motor is shot.
It is probably a capacitor problem. Check inside the outside unit. you will see a round cylinder with three groups of terminals on top. If the top of it is dome shaped it probably needs to be replaced. You can check it if you have a microfared tester. However if it is poofed out it probably is bad. If this is not the problem you will probably have to replace the fan motor.
If the humming is your compressor running (feel the large copper line going into the unit, it should feel cold aftter a few minutes of run time) then the fan motor or the capacitor or both need to be replaced, check for voltage to the fan motor when the unit is "humming" if it has voltage and will not start replace the fan motor and the capacitor. hope this helps.
FOR QUESTION 1: They do run independantly. What will happen when your compressor is running but your outdoor fan does not, the pressures in the system will go really high and compressor will overload. That outdoor fan is used to disipate all the heat that is transferred from the inside to the outdoor unit.
FOR QUESTION 2: If you hear humming it can be 2 things. FIrst one is that that capacitor went bad. Dependiing if its a dual run capacitor(which helps both compressor and fan motor) or they both have individual capacitors. The second would be a bad fan motor. OPen your service panel outside to the AC. Find your capacitor for you fan motor. if there are 2 , locate the one that goes to your fan motor. Check it out(if its blown physically youll will notice it like really bubbled, like swollen) then change itout. Or you will have a dual run capacitor that runs both compressor and fan motor. It will have the terminals marked (Fan, Common, Herm) Bsically check your capacitor mfd(micro fared rating, it will say on the capacitor what its rated) Get a multi meter and put in the "MFD' selection. Before you check any capacitor you have to discharge the the voltage charge it has. Use an insulated handle screwdriver and just place the metel part across the capacitor leads. Basicall short them out. Then proceed with checks...hope this helps( remember to always pull the disconnect out from the box outside to cut power)
check the capacitor of your condenser fan,if busted replace,although thats the common causes of hummimg motor,it can't start,consider also after replacing capacitor still hum,check the motor start winding,and the supply from the source of relay in control panel.have a nice day
a very subtle hum or buzz is normal and is the transformer that creates 24 volt control voltage continually. some are noisier than others . sometimes a tap or bending of the transformer will tweak the metal enough to make it quieter. they can also get loud if incoming voltage is not correct. incoming 120 volts on a furnace is not usually a problem but the transformers are usually wired to the available incoming 230 voltage or 208 voltage if it is a heat pump or electric heat. If it is powered by 230 or 208 volts as most heat pumps are ,then you need to verify which you have and connect the appropriate leads from the trans former to power . it tells you on the side of the transformer which to connect to 230 and which to connect to 208. tape or cap off any unused leads.since you have not mentioned any performance problems i assume the fan does come on when called for and that it is not the loud hum you hear. switching the fan switch at stat to on should bring the fan on right away. if it doesn't then you may hear a loud hum and then youll need to check the fan motor and capacitor. but it sounds like a noisey transformer from here.