Ancient furnace motor won't start

[Thefamilyman]

I have an old furnace from what appears to be the 70's. The blower motor quit working. The motor was simply humming and very warm so I changed the motor out with a US Motors brand motor. The wiring schematic on the motor was less than stellar. In lieu of stating hot/black wire etc it said "ungrounded line". I took that to mean hot wire and hooked it up accordingly.

The new motor is doing the same thing (Simply humming.) Any ideas? It's 48 degrees in my house!

 

[Wuzzat?]

If it uses a run/start capacitor that may be the problem. Can you carefully start the motor spinning by hand?

 

[user 4883]

You should have gotten a new capacitor with the new motor. If not, replace the old capacitor per the specs for the new motor.

 

[Thefamilyman]

It's my assumption that the capacitor is attached to the motor which I replaced. There is nothing beside the motor which mounts directly on top of the squirrel cage. Tomorrow I plan to check the current leading to the motor, and then check the motor itself by attaching a cut off heavy duty extention cord to it. Past that, I am out of ideas.

 

[joechuckg]

Rescue motors don't come with capacitors. You have to buy it seperatley it should say on the motor box what size cap the motor will need two brown wires

 

[user 4883]

joechuckg; you are correct. It used to be that 99% of the replacement motors came with capacitors but, not to save on cost, they no longer include them with the motors. Can't tell you how many times I've recently purchased a new motor only to find out I forgot to order that cap with it.