Just replaced 3 wire fan motor with 4 wire fan motor and additional capacitor. The original motor had the brown and purple wires connected to the original capacitor. For the new motor, I have the two brown wires connected to the new added capacitor, the black wire is connected to the same wire as the previous black wire was, and the white wire is connected to the original capacitor. With all this completed, fan is turning slow. What should I do now?

Just replaced 3 wire fan motor with 4 wire fan motor and additional capacitor. The original motor had the brown and purple wires connected to the original capacitor. For the new motor, I have the two brown wires connected to the new added capacitor, the black wire is connected to the same wire as the previous black wire was, and the white wire is connected to the original capacitor. With all this completed, fan is turning slow. What should I do now?

white wire is connected to the original capacitor

Wire exactly as shown on the diagram that came with the new motor. Your brown wires are OK I believe but the other two wires go directly to the load side of the contactor that also activates the 220 volts for the compressor.

Make sure the motor is turning the correct/same rotation as the old one.

Wow, moved white wire to other post on capacitor and now fan is turning a proper speed.
Thank you, Hvac1000, for prompt response!!

Glad you got it running correctly. Stay cool.