Clues

I thought I'd revive this thread as my washer fluid low warning light was on for a week even though the reservoir was full. Yes, I've been an avid fan of Rain-x for several years... and yes, I am very disappointed that their new formulation causes this fault.

I ordered a new sensor for $5 on Amazon (URO Parts 7M0 919 376). Others say you can successfully clean the sensor, but I figured for $5 I'd rather just swap in a new one.

The process is fairly straight forward.
-Remove front passenger wheel
-Remove the tire/fender liner. There are several torx screws and two bolts (10mm I think) that hold the liner in place.
-The reservoir sits between the wheel well and the passenger compartment. I initially tried to do the swap without removing the reservoir from the car but it's a tight space and I was unsure how the sensor was seated - so I opted to remove the reservoir to better see what I was doing.
-The reservoir is held in place by two torx bolts. You'll need a ratchet with torx bits because there is not enough room to get a torx screwdriver into the fender area.
-Once both bolts are removed, the reservoir will slide down and out of the fender area.
- Remove slowly as it's attached at a few points:
-the fill hole at the top is attached to a flex tube. Just pull it out.
-the sensor is attached to a harness. Squeeze the sides and pull to remove.
-the pump snaps into the molded space of the reservoir - once you pull it up and out from the molded space, you will break the grommet seal for the pump and the washer fluid will come gushing out. Have a bucket ready. It is a small hole so the fastest way to empty the reservoir is to put your finger over the pump hole and the turn the reservoir upside down over the bucket and let it drain from the larger fill hole.

-Use a plastic door panel remover tool to pry the old sensor away from the rubber washer/grommet. A srcewdriver is tempting but if you tear the rubber, you'll need to go buy a new one...

Reinstall in reverse.

The old sensor was covered in an oily gel. I washed the metal prongs with vinegar and a brillo pad and will keep it just in case....

efett

Had the same problem with my Q7 and when it was in for service the tech pulled the sensor and wiped it off with rubbing alcohol. The light hasn't come back on and haven't used anything but generic blue fluid since.