Rear wiper playing up

[titch]

The rear wiper on my 2001 hdi has just started to play up. Got in it this morning put it on to clear the rear screen and nothing, i had a quick look at lunch time, and it seems if you open and then close the boot lid it starts working again. Then on the way home i went to put it on and it wouldn't work again, so pulled over and hit the boot lid in the area of the wiper and it worked again and has been ok since.

Going to have a look tomorrow if the weather is ok and check the plugs on the motor, Is there any common faults to look for, or is it time for a new rear wiper motor??

Cheers Titch