When i bought my Xantia`99 estate, the rear wiper try to make some moves.. for a minute or two and die and that is why i decide to open it anyway and found problems and their solutions.
1. take the unit out
2. put 12V direct to the white whire and ground to the black one
that will remove any unknown factors because give 12V straight to the motor. In my case even that did not make the motor to work properly
3. Open: with small 3.3mm(for M4) or 4.2mm(for M5) make holes trough that pins that lock the top cover. After that in the holes which come in the body make M4 or M5 thread because the bolt heads are small enough to fit nice. M6 will do the job also, but the bolt head is quite big for that places.
4. Inside:
remove the plastic wheel:
and check its tracks and connecting contact pins soldiered on the main body.
Use the hummer and gently hit on the wiper axis(from the wiper`s side) to go little out. Then use WD40 or bike oil spry to clean the bearing, and really well the metal teeth. In my case there was full of rust and that make all that movement really hard for the motor. When you feel it move absolute easy, check how is the gap or back lash in the worm gear axis. There is small inside hexagon nut to adjust it. Add grease and fit all together back.
5. Control relay: Remove the blue plastic cover with small screw driver, but carefully to not brake it
and check for broken points:
If that is OK, carefully remove the spring which keep the coper plate in the induction coil, then take out that plate and clean the contacts inside:
After that refit the plate, and add little grease on the corners that plate is moving( that U-shaped part), and move that thick coper wire which is soldiered somehow to stay in the middle of the plate.
Make final test on place before to close. For me that safe me from buying new motor for now, hope will hep to someone else!
Good luck
