This may just be luck on my part but, if you have a similar problem, it is worth checking before replacing anything.
The rear wiper wasn't wiping intermittently - it was wiping constantly on the intermittent setting - and would park wherever it was switched off. As my rear window is out I decided to remove the motor assembly - the motor and wheelbox are off a Porsche 928 btw - which is on a steel frame held by two allen screws visible behind the tailgate, and two 11mm bolts (actually they are very big screws!) by the partition window. You have to remove the trim panel first, if you still have one, held in place by 4 screws and some adhesive along the rear edge.
The motor intermittent function is controlled by a timer relay, behind the driver's side kick panel. This seemed to click OK when the intermittent setting was first turned on, but before I could tell if it was fully working I needed to get the motor parking correctly. I removed the wheelbox cover and on the inside of the cover are three sprung wiper contacts which rub against the drive wheel. This has a metal surface, with nylon non-contact areas to control intermittency and parking. In my case, the wheelbox was pretty full of grease all over the surface where the wiper contacts rubbed. I placed the cover back on and tested resistance between the three wiper contacts - there was none, despite the inner contact sitting on a nylon surface. So I removed the grease from the surface and the wiper contacts - and cleaned everything electrical up. I refitted the cover and now there was resistance on the inner wiper contact. Wired it all back up, rested it (mechanism upwards!) on a small stool I had put in the boot, and switched on. Everything now works as it should with the timer relay ticking to initiate an intermittent wipe, and the wiper parking correctly.
Incidentally, I'm going to photograph the trim panel and send it to someone who may be able to 3d print it as these are fairly flimsy and, unless you're lucky, unobtainable. Is anybody interested?
For all those wiring gremlins we love, this is the place to discuss them.
Moderator: Board Moderators
1 post • Page 1 of 1