My wiper comes on whenever it likes.
It randomly wipes whenever it wants. I
believe there may be something wrong with
the turn signal switch arm
It could be a loose connection somewhere on the switch on the turn signal arm. Or somewhere else on the circuit. Buy a circuit tester and hunt the culprit down if you are doing the work yourself. Basic knowledge of electrical theories helps.
Search Mercedes-Benz 190-Class Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Mercedes-Benz 190-Class Experts