JOHN DEERE S120 Mower Electric Pto Clicking

PTO Engagement Switch

The internal copper contacts of the pull-knob switch often develop carbon buildup or 'pitting' from repetitive arcing. This creates high electrical resistance that allows enough voltage to trigger the clutch solenoid but insufficient current (amperage) to maintain the magnetic bond, resulting in rapid cycling or clicking.

Electric PTO Clutch

Electromechanical failure occurs when the internal coil windings develop a partial short or when the air gap between the armature and the rotor exceeds the specified tolerance due to friction wear. If the gap is too wide, the magnetic flux cannot reliably pull the plate in, causing it to strike the rotor and bounce back, creating a metallic clicking sound.

12V 300CCA Battery

The PTO clutch is the highest electrical load on the engine's charging system. If the battery has high internal resistance or a failing cell, it may hold enough surface charge to run the fuel solenoid but will suffer a terminal voltage drop when the PTO is engaged, causing the clutch solenoid to chatter as it enters a rapid 'engage-collapse' cycle.

SKU: TY25878