My furnace was starting and then shutting off About a month ago which I was able to figure out(with internet help of course:) ) was do to a faulty capacitor. I replaced the capacitor and everything worked fine up until now. It has started doing the same thing again. If I spin the motor it will kick on and run but won't work on its own. Any idea what would make a capacitor go out so soon? Is there any way to figure out how to keep the fan going or bypass the capacitor? Thanks in advance... Tim

Have you tested the capacitor to see if that's what bad it could be a dead spot on the motor.

Have you tested the capacitor to see if that's what bad it could be a dead spot on the motor.

I haven't tested this capacitor but the first one that went out a month ago was tested and was bad. I had another person thinking along those lines also until I told them that the first one tested bad. I guess it could still be a bad spot on the motor but would it start on its own as long as it was not on that spot? I started and stopped it several times and every time I have to push start the motor. Thanks for the response... Tim

Do you have the right size capacitor for the motor? You can go up 10% for a run but you can't go lower on a run capacitor. If they won't last you will have to replace the motor.

Do you have the right size capacitor for the motor? You can go up 10% for a run but you can't go lower on a run capacitor. If they won't last you will have to replace the motor.

I'm pretty sure it's the right one. I replaced the motor and capacitor a couple of years ago. When this one went out I took it with me and had the guy at the parts counter test it and give me one just like it to replace it with. Will the motor wear down the capacitor if something's wrong with it? As I said above, the motor is only about two years old. I don't know if this matters but I went from a 1/2 horse motor to a 3/4 horse motor when I replaced it. A neighbor of mine at the time said that the motor would spin faster and put out more air flow. As it turns out the a-coil was completely clogged which is why It would not blow through the vents. Since then I have had the compressor and a-coil replaced. I'm able to work on these things with advice but am by no means any kind of tech.

If all else fails,, and you`re not sure,, the tag/sticker on the side of the motor tell the size of capacitor that is needed for the motor, I know it's a pain to pull it out to look-see but then you will be sure

= Is there any way to figure out how to keep the fan going or bypass the capacitor?
No. You cannot 'bypass' the capacitor and it MUST be the correct one. Someone posted that you can go up 10% but it's actually 6% increase, but never decrease. Not only does the microfarad rating have to match but so does the voltage. Example: 10 microfards @ 370VAC.


I don't know if this matters but I went from a 1/2 horse motor to a 3/4 horse motor when I replaced it. A neighbor of mine at the time said that the motor would spin faster and put out more air flow.
Going from a 1/2 horse to a 3/4 horse does not always meaning an increase in RPM. You can have, for example, a 1/2 horse motor running at 1075 RPM and likewise you can have a 3/4 horse motor running at that same 1075 RPM. Unless you put in a motor with a higher RPM rating then air flow will most likely not be affected. On that note, if you did replace your motor with one of a higher RPM rating then chances are that is your main problem. That blower wheel is designed in such a way that if you put it on a motor putting out more revolutions then that motor will overamp. This can cause internal damage to the motor and possibly the capacitor.
For what it is worth and t has been said 100 times on here, higher blower speeds does not necessarily equate out to improved heating/cooling. In act the exact opposite is usually the case. I sugest that you find a reputable service company in your area and have them install the correct motor and cap, either aftermarket or OEM.