Lennox Model G23Q3/4-100-2 Furnace Blower Motor Problems

[clattin]

Late last night, I heard a "humming" coming from my furnace so I took the covers off and the blower motor wasn't spinning and was just getting a humming sound from it and got a pretty good nose full of a hot ozone smell, So I shut the furnace off at the switch for the rest of the night.

Started troubleshooting this morning and based on some research, thought for sure it was going to be a bad capacitor.  I could freely spin the fan blades (and no wobble in them or grinding sound) and when it would hum I could get the blower to start spinning by using a wood dowel to give it a "jump". So I discharged the capacitor and checked it with my multimeter and got about 7.6 microfarad (7.5 microfarad capacitor).  So, I thought, well its not that.  I then checked the resistance on the leads to the blower motor itself (GE 5KCP39MGR590BS 1/2 HP) and got 2.0 ohms and 4.0 ohms between white-red and white-black.  So I just turned the fan on again and it seemed to work fine.  So I left it switched on and activated the furnace and it went back to the humming noise and no blower.

Thoughts?

FYI: in the last month I installed a furnace mounted humidifier on the outlet duct (not the cold air return).  Could the new humidity maybe be causing a problem with the blower motor?  Again, no grinding noise and the fan spins freely manually.  Maybe the motor needs to be oiled??

Thank you!

Chris

[A & G Enterprises]

i would check the motor amps when the motor is hot i suspect a bad motor or capacitor when its runs for a while and it heats up

[clattin]

Ok, so after the furnace has run properly after several minutes and gets warmed up and shuts down.  Then when the thermostat called for heat again, the motor started humming and not spinning and the leads to the motor are pulling about 15 amps.  

 

So, bad motor?

[clattin]

Must be the motor.....put a brand new capacitor on and still a no go.

 

Chris