Check for resistance between No.2 and No.3 terminals in each switch position.

Switch  | Connector terminal  | Resistance (±5%)  | 
Volume Down  | 2 - 3  | 6.81 kΩ  | 
Volume Up  | 2 – 3  | 4.61 kΩ  | 
Mute Off  | 2 - 3  | 3.11 kΩ  | 
Mode  | 2 - 3  | 2.11 kΩ  | 
Seek Down  | 2 - 3  | 1.11 kΩ  | 
Seek Up  | 2 - 3  | 430 Ω  |