The front wiper I'll assume until you answer Fred's question.

Wiper motor does indeed have a mind of its own, although it is a low-tech mind, made up of cam and contacts. The usual progression is to blame the relay, 'cuz it is simple to change and not too expensive, then to try a stalk switch, 'cuz it's easy to change and only slightly more expensive, and then to replace the wiper motor, which gets even more expensive and requiring of some contortions to disconnect.

Why not have a try at the simple first: remove the cover on the wiper gear box and clean up the copper contacts. Worth a try, and will cost you $0. That's where the park brains are.

Notes on 240 Volvo Windscreen Wipers
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Art Benstein near Baltimore

To err is human, to moo bovine.