opelbits· Detritus Maximus
There is also the possibility that after all these years the wiper motors need to be 'overhauled'. This would mean having the stator and such turned and cleaned, new brushes, new wiring/terminals, etc. All of these parts can get corroded, worn, or dirty and cause a reduction in performance. A good electric motor shop can do much of the work, usually for a decent price.