hi i had same problem .the problem is on the motor itself if you remove the black casing around the wiper motor you will see a white curcular disc which will release quite easily.just be carfull not to dammage the wires on the face of the disc.once this is removed you should see 3 or 4 copperfingers that connect to a metal disc which will probably be coverd with dirty dry grease remove all the old grease and replace with new.
i had to slightly bend the copper fingers out slightly to make good contact ,replace all parts and jobs done .this might not work straight away as copper fingers may need to re grove through new grease.