The rear wiper in my 2007 Audi A6 Avant (wagon) has been having intermittent problems. The wiper will stop randomly and other times won’t work at all. It has had the largest problems when in the sprayer mode. After some research online it appears that there is a sprayer tube that runs through the motor spindle and it is common for that tube to crack. Not wanting to spend $300 for a new wiper motor assembly I decided to give it a go and try to repair it. The wiper motor is operated on a CANBUS line, so there is an internal PCB that controls the behavior of the wiper arm. The intermittent failures and sporadic operation led me to believe that there was an internal water leak that was shorting out the PCB.
Upon removing the interior trim piece of the rear lift gate I saw water stains on the plastic. This supports the hypothesis that the motor was leaking internally when spraying.
With the motor removed it was clear that something wasn’t right. There was rust on the exterior of the assembly:
After removing the Torx screws and removing the cover I was presented with a huge mess of rust and old grease:
Tracing the electrical leads back I found that the expected PCB was hidden under a separate cover. I removed the plastic and found the board with what I believe to be a CAN controller. It is an International Rectifier 98-0344, but by the lack of an available datasheet online I believe it to be a proprietary device. That means that you could not easily swap the chip where it to have been damaged. Anyway, the board was covered in rust and mineral deposits; there had clearly been washer fluid leaking onto it.
After removing the spindle and gear arm assembly I discovered that the tube was not broken as I had expected. This meant that the leak was coming from somewhere else, but it also meant that I could easily salvage this motor.
Unfortunately the gears were also extremely rusted, so they would need a lot of elbow grease.
Next step was to remove the motor from the gearbox. It wasn’t in bad condition, and just required cleaning off the worm gear. While I was at it, I removed the plastic piece that holds the brushes and cleaned off the carbon deposits. No sense in leaving anything un-done since I was already in there.
With everything else removed the big gear became accessible. The plastic wasn’t damaged and it also only required some quick cleaning.
I used MG Chemicals Safety Wash II to do the cleaning. This worked well for most components with some added help from a toothbrush, but wasn’t going to work on the spindle and gears. For that I ended up using a ton of PB Blaster to make a bath and soaking the rusted components for about an hour. After that I removed them and got to work with a steel brush. The brush was helping, but wasn’t working as well as I wanted nor was it getting in between the gear teeth. To take care of the rest of it I pulled out the Dremel with a 462 Rubber Polishing Cone Point tip. This made short work of the rust and was able to get into all of the gear teeth. The final result wasn’t shiny, but it was a heck of a lot better and had quite a bit less resistance to movement.
I forgot to take a picture of everything all cleaned up prior to assembly, but I got things put back together and added generous amounts of wheel bearing grease to keep everything well lubricated. I also added some rubber sealant on the joint where the spindle tube meets the hose connector on the back plate. This is my guess as to where the leak was coming from. Here is the final result:
Once the motor was re-installed I gave it a test. Both wiping modes appear to be working correctly again, and the motor is a heck of a lot quieter than it used to be. I have no idea if it will leak again, but even if it does I should have gained some extra time before having to lay out the money for a new motor. Heck, I’ll probably tear it apart again if it fails before doing a full replacement. Time will tell if it’s a permanent fix or not.