The furnace blower motor makes a loud hum when the blower starts up. This happens in AC or Heat modes. I have replaced the run capacitor, which made no difference. Once it starts up, it runs relatively noiselessly (just the moving air noise of a normal blower).

My question is: I now have a spare capacitor and both caps have multiple 1/4" tab terminals on each pole. Can I stack two capacitors and will this stop the hum.

The cap is 7.5uf/370v, as called out in the manual.

G24M 3/4-100A-2 is the Lennox model number.