 Turn off the main water supply to prevent water flow during repair.  Remove the bathtub spout or diverter handle by unscrewing or pulling it off carefully.  Disassemble the diverter valve to access internal parts such as the gate, rubber seal, spring, or valve stem.  Inspect all components for wear, damage, or mineral buildup; clean parts using a brush, file, or vinegar soak to remove debris and grime.  Replace damaged or worn parts like rubber seals or diverter gates if necessary.  Reassemble the diverter valve and tighten screws or nuts securely without over- tightening.  Turn on the water supply and test the diverter for proper water flow and absence of leaks.  Adjust the diverter position if needed to ensure smooth switching between tub and shower flow.