I purchased a Dayton 4M205G fan motor to replace the original motor in my Armstrong AC. I also purchased a new capacitor. The original A.O.Smith motor had 3 wires. The new Dayton, and the replacement from A.O.Smith, both have 4 wires (plus the rotation and ground wires). Do both brown and brown/white wires go to the same contact on the capacitor? Does the old capacitor completely replace the existing capacitor with all existing wires connected the same as they are currently?

I'm not sure if this will work or not but someone else asked the same question on another web site. He decided he knew what he had to do.

Replacing condenser fan, wiring questions (with picture) - DoItYourself.com Community Forums

I figured it out. The new capacitor is needed along with the old capacitor. The extra wire (brown/white) is the hot wire to the capacitor. Both brown wires attach to the new capacitor on separate terminals. Make sure that you secure the new capacitor in place.

If Perito reads this, please post it to the other help site.