How to check a fan motor start capacitor?

It probably is the capacitor but no guarantees as the insulation of the motor windings could have broken down or there might be another fault. Proper checking with an insulation tester is advisable.

If the capacitor is merely a start capacitor and not a start/run capacitor the motor should perhaps hum a little when switched on and then run normally if the fan blades are given a vigorous turn by hand.
There are several ways of arranging the motor circuit and some knowledge of these would be useful. You could have the capacitor tested by a local motor expert.

Capacitors bought as spare parts from appliance manufacturers tend to be very expensive. Capacitors are usually bought in by such manufacturers and replacements can be sourced much cheaper direct if the type and values and the maker's detail are present on the capacitor case, otherwise you will need the services of a motor specialist to determine the values for you if the information isn't available elsewhere.

Sounds like a bad motor. I don't know if your blower motor has an external starting capacitor and / or a running capacitor. If There is a starting capacitor and it's faulty , that would prevent the motor starting and turning.

the answer to your problem is most likely the motor start capacitor. A AC motor can run in both directions. The start capacitor is used to cause the current to lag behined the voltage which determines the direction the motor will turn. Its posible the start and run capacitors are in one can. so changing one will change the other. However look for a wiring diagram. Do not asume that both capacitors are wired in properly. They may be fighting one another causeing premature failure.

The motor may have a capacitor that has failed. Start Capacitors and/or motor winding "shades" are used to determine the direction of rotation, if the capacitor is checked and is defective replace it, if the capacitor is tested and is functional the fan motor may need to be replaced. it is helpful to include the model and serial number of the unit to ensure the wiring diagram is correct for your fan.

The problem you're facing here could quite possibly be more than just replacing a motor. You could have circuit damage which may be the reason that the furnace quit working. You can try testing the fan that is currently installed. Make sure it is working first before buying new parts. Determine the required voltage for your fan and supply that voltage to it momentarily. Do this while the fan is completely isolated from your furnace (unplug any leads from it to the furnace controllerboard) You may want to get assistance when working with electrical current so you don't accidentally cause harm to yourself and/or your furnace.

try to help the fan start with a screwdriver. If it starts, you likely need to replace the capacitor. However, sometimes this does not work and you will still need to replace the motor. If the motor is bad in one spot it may work and not start when it stops on the bad spot.

Two possible problems here.
1. you have a bad condenser fan motor. average cost $140.00 for the part plus installation if you can't do it. just buy the motor you most likely will be able to use the existing fan blades.
2. you have a bad run capacitor on that fan. avg cost $5.00 - $35.00 plus installation
In my opinion if you're handy and safe with electicity save some money, if not have it done.
check out grainger.com for the parts they're very reasonable. for the fan you'll need to get specs from the defective unit like amp. voltage rpm. its all on the unit itself. for the run capacitor you'll need the same. all the info u need is on the parts. search the site for run capacitor or condenser fan motor.
good luck hope this helps

if the AC is coming on with no air output the problem is that although the compressor is running - the fan motor is not.

This can be because of a 'switch' malfunction, a wire burnt into, a bad fan capacitor or a bad motor.

Of the four possibilities the easiest two to identify are the 'wire that has burnt into,' and a bad fan capacitor. A wire that is burnt into is obvious and so is (sometimes) a bad fan capacitor. A fan capacitor which btw - is a little module (usually gray or silver in color) with wires attached to it. I would check all my wires to it and to the fan motor and anywhere else I could in the unit. Also examine the fan capacitor itself - looking for burnt damage or a 'bulge' in the module which are direct symptoms of a bad fan capacitor.

If it's the capacitor you can remove it making sure you mark your wires in such a way you can connect them up after acquiring a new capacitor.

You can buy capacitors at any Air Conditining Supply house - and they will run about $15-$25 or less.

A bad motor is usually indicated by the motor 'not starting/running' and/or 'the motor being hot to the touch' - there's not much that can be done these days if the motor is bad but replace it. And unless you're really mechanicaly inclined and have plenty of specility tools I would not attempt it. A Service Tech is the best bet here, and you're looking at a repair bill of around $150-$250.

A 'switch' problem is really not that likely but for a nominal fee (usually around $35-$50 you can buy a switch and change out the old one. Like I said this is not likely the problem and I would probably not do this on a hunch.

good luck!

It most likely has a faulty capacitor not allowing it to start. Remove the light kit or the cap where the light kit mounts, the speed and reversing switch will be in there along with a capacitor. You should be able to buy a replacement capacitor at most home improvement stores.

If you have power to the fan and the fan won't come on, then its bad. You don't have to do another check. You will know if the capacitor is bad by turning the power on to the unit and taking a stick to start the fan. If the fan starts running after manually spinning, then the cap is bad. If not, the motor is bad.