Defender Wolf wipers won’t stop

[Adamm]

Hi all. This is my first post as I feel I am chasing my tail with a wiper issue on my 1998 wolf. The problem is, with the intermittent relay in, the wipers get to the park position and either slow or blow the fuse. They won’t stop unless the fuse is blown or ignition is off regardless of whether the relay is in or out. I have replaced the control stalk and relay however the problem is still present. Having read lots of posts regarding the motor park switch I had the motor tested with a view to getting it reconditioned however they found no issues on the test rig, the motor parked fine. Does anyone have experience of this as I am doubting the parts I have exchanged ? If not this then the vehicle wiring. I am not sure if the park switch common should be switching an earth or supply and this would be helpful to know so I can test the only wire which runs from the motor park switch to the relay, brown/light green. 

Any help would be most welcome. Many thanks