Intermitent wiper always on

[Dead Parrot]

Very likely most 35 year old modules are failing the same way. Probably a bad capacitor that is part of the timing circuit. Take one of the dead ones apart and see if any capacitors are showing signs of leakage or bulging.

Also check for burn marks on the circuit board. Possible the wiper motor is drawing too much current. Enough to burn out the board, not enough to blow the fuse.