Punto wiper motor stuck on

Fiat punto '52 plate.
Hi all. My son came home this afternoon with the cry of Da-ad. The wiper
motor was running continuously with the ignition on. I check Haynes and
there are three relays - one in the switch, one in the fusebox and one at
the motor. I swapped the fusebox one for another, but it made no difference.
I dismantled the wiper switch assembly on the steering column and found a
nice little printed circuit board with a relay soldered on. I did not
investigate the motor.
As a temporary measure I have fitted a switch onto the motor supply wire
which isolated the power until I figure out a more permanent solution.
Am I right in thinking that the fault is caused by a sticking relay?

Any help would be appreciated.
Thanks
Davy M.