Possibly. Was the old motor completely dead? If not, I'd just plug it in temporarily to see if it does the same thing. That way you can narrow the fault down a little. There's a permanent live to the motor and a park switch so that the wipers park after you switch them off at the steering column stalk. That can go wrong and could result in continuous wiping if its contacts aren't separating. Yes, wiper relays go wrong and have a limited life They're more than just a relay, there's a printed circuit board in there too so as to organise the intermittent function So they're somewhat more vulnerable than a bog standard relay. I've never formally tested my wiper relay, I've just got another one and plugged it in, which is a bit lazy of me I suppose. But with readily available small components it's not worth spending days repairing them.