Having more than one motor lead energized at once can damage the motor - it's unlikely that's the issue though.

If the bearing starts to fail, the motor can draw excessive current and overheat.

You already ruled out the capacitor.

In all likelyhood, the motor needs to be replaced.

 

Thanks for taking the time to reply. I had a horrible feeling it could be the motor itself. So the fact that it's overheating but still working at the temp set on the thermostat can still mean a bad motor? As a total novice it was my guess (as you see from my first post) that a bad motor wouldn't do anything at all except maybe overheat. I take it that's not necessarily the case? :confused1:

 

As the bearings gets tighter, the motor draws more and more current to maintain rpm until it starts to overheat.

You can see if it has oiling ports. Normally there as little plastic caps you remove and add a few drops of electric motor oil. You may be able to extend it's life.

https://www.3inone.com/products/motor-oil/

Do make sure only one tap is being energized. easiest to test with a clamp meter.

you should only have one line, one speed tap wire and the capacitor wires with current flowing, the speeds not energized should have no current.

 

Ok, here's a photo of what I have back there. Does tie in with what you're saying I should have? (I'm not sure what the speed tap wire is, sorry) Again, forgive the noob questions, I'm just finding my way around this and appreciate the help you're giving.

EDIT Here's a link to the photo in case I'm not allowed to post pics yet

http://oi68.tinypic.com/2ezgzkp.jpg

 

i can't see anything , no pic or video off of link.

 

Strange. How about now?

https://tinyurl.com/y98gdr7b

 

I see a pic with the capacitor now.

If you spin the wheel by hand, how much force does it require?

 

Thanks for persevering with me. Spinning the wheel takes no effort at all and the blades will spin for some time with no sound.

 

I still suspect the motor is bad. With a good cap, that's the only real possibility i see unless it was miswired or something. (though it if was, should have burned out by now)

How many wires are going to the motor and connected?

I wonder if it's wired for one speed or it uses a different speed depending on the mode.

See if you can find a schematic on blower access panel - post a clear picture if possible.

 

Ok, the only wires coming from the motor are these. A green (ground?), the black & red wires on the side of the motor, plus a brown and an orange leading to one side of the capacitor. There's one more orange wire leading from the other side of the cap into the panel on the front. There are no other wires around the motor and nothing is disconnected.

https://tinyurl.com/y9uakbrg

As for schematics, unfortunately the below is the sum total of everything on & around the furnace :sad:

https://tinyurl.com/yccoehhr

 

That extra orange wire coming from the cap to the front panel, is it connected to anything? It looks like it was a 4 wire motor was installed in a 3 wire application. It's common, but usually you'd disconnect that extra orange wire. It's probably not the problem though, as it would have stopped working long ago.

If you plan on changing it yourself, order a new motor online. The old motor will likely keep going for a little while longer, but I wouldn't give it the whole season.

Cheers!

 

possible the motor was changed and they put the wrong hp, but it doesn't look like a new.

still leaning towards it being bad.

 

Probably the winding insulation is wearing out, and causing the over heating. Not uncommon for a motor to run and over heat, but yet spin freely by hand.