Genuine Kohler Regulator Rectifier 20 to 30 amp, FW W/O, 25-403-39-S - 2540339-S.

Replaces: 2540305S, 2540305-S, 25-403-05-S, 2540308S, 2540308-S, 25-403-08-S, 2540320S, 2540320-S, 25-403-20-S, 2540321S, 2540321-S, 25-403-21-S, 2540329S, 2540329-S, 25-403-29-S, 2540332S, 2540332-S, 25-403-32-S

This latest rectifier-regulator, has a ground lug and built-in over-voltage protection that is self-resetting. The over-voltage protection prevents possible damage to other electrical components if an engine is jump-started. This regulator is especially recommended for use on EFI engines, except on Walker mowers where there is insufficient clearance for it to be used. When replacing an earlier regulator, like part number 2540305S, just use the new regulator. To replace an older regulator, which has short wire coming out of regulator use kit 24755144S, which includes the new regulator and the necessary conversion pieces.
 

The protective circuit in the new regulator works much like a circuit breaker. If excessive voltage is detected, the protective circuit breaks/opens the charging circuit (B+ output) to prevent the elevated voltage from reaching other components. Excessive voltage can be due to spikes caused by attaching or disconnecting jumper cables, or by loose battery terminal connections. It can also result from a defective battery that is not capable of holding a charge.

Important Service Notes
Once the circuit has been tripped, the circuit will discontinue charging for approximately 20 seconds. After 20 seconds the regulator will resume charging. If the over-voltage condition has not been corrected, the circuit will discontinue charging for another 20 seconds. This condition will repeat until the overcharge condition is corrected. Stop the engine. With the engine off, test voltage across the battery terminals. If it is below 12 volts, use an auxiliary charger to charge the battery.
When the battery has been charged, start the engine and test to confirm that charging output has been restored. Allow the engine to run for several minutes and test again. If the battery is defective, the B+ circuit will trip repeatedly until the faulty battery is replaced.