Slow starting indoor fan

Hi all - I have an indoor fan motor for my gas furnace that is around 15 years old and last night I noticed that when the heater kicks in that the fan motor was making a humming noise like it was straining to start. If I gave the squirrel cage a push it started running fine. After I did some checking I found that the fan was wired to the high speed lead. I re-wired the motor to the medium speed and it seems to be working. I cycled it about 6 times and it started every time. When I got up this am my wife said the fan was making the "noise" again. I cycled the fan several times and so far today it has started with out a hitch.

Now for the questions. Would the start capacitor cause this condition? Is the fan motor on it's last leg? Anything I could check with a vom meter?

Does the squirrel cage rotate freely or is there some resistance. The problem could be the motor or the capacitor. If you have to change out the motor, it is a good idea to change the capacitor at the same time. With that in mind I would not hesitate to go ahead and get the capacitor and throw that at the problem. If you are getting some resistance when you spin the squirrel cage, your motor will probably seize up very soon. I would check on the availability of both the replacement motor and capacitor now. If either of them fail soon, you'll want to be able to get your hands on a replacement quickly.

I had a similar experience. My motor gave an early warning sign like yours. It stopped one day and I gave the squirrel cage a spin by hand and everything started working again. The next day at 4am, the motor seized up for good. I called a local HVAC repair company that also sells parts over the counter and got a replacement motor and capacitor. The heat was back on by 10am.