Starter motor problem

On several occasions over the last few months, Patience's starter motor has failed to engage and turn over the engine.  Rather than the engine roaring into life, only a rather unsatisfactory click emanated from the starter motor solenoid when the ignition key was turned fully clockwise.

This was diagnosed as either a low battery, loose battery contacts, a fault with the solenoid or the motor itself.  The first cause was eliminated by checking the battery state of charge, which was fine. The second cause was also eliminated by checking that all the battery connections were tight and in good order - they were.  I then disconnected the cables from the solenoid (photo 1) and removed the solenoid from the starter motor.  There was a slight looseness in one of the the electrical connection studs on the top of the solenoid (photo 2) which was corrected by carefully tightening the lower of the two nuts on the stud (not shown in photo 2 but just visible in photo 1). Unfortunately, it's not possible to take the solenoid apart, as it appears to be a factory sealed unit, so it wasn't possible to check the condition of the internal contacts.

Solenoid in place on the starter motor

Solenoid removed, showing electrical connection studs

After cleaning the studs and spade connectors, the solenoid was replaced on the starter motor and the electrical connections restored.  Although I hesitate to claim that the problem has gone away, to date it does seem to have done the trick.