Of all the little doodads on my 2005 XK8, the rain sensing wipers are among my favorite. Really like how they adjust their speed for the intensity of the rain. Lately, though, they turn on sometimes when I go over a bump. I assume the sensor is a bit loose, but am not sure how to get at it. Any hints would be appreciated. Having to turn the wipers on manually is just exhausting. Thanks!

 

Another reason may be that when the wipers "park" in the horizontal position on the windscreen the motor is stopping too close to the park switch and going over the bump allows the wiper motor to contact the park circuit.
This is the circuit that allows the wiper to "finish" wiping the screen until it parks. It's the feature that makes the wipers finish wiping even though you only blipped the wiper switch.
I would look for a mechanical problem such as the wipers hanging up on the base of the windscreen. They might not be "parking" correctly.
Good luck.

 

No, the sensor is partially away from the glass. you can seee the sensor and how well attached or not from outside the windshield. You need a new disc and it must be totally clean sensor and glass with no air bubbles when you attach it. Pop the covers off around the rear view mirror to access and youll see it. remove it from glass and connector, clean and reattach

 

This is the part number for the adhesive disc: LJD3850AA

 

Thank you Brutal and Steve, I have been experiencing this same thing, and just figured it was something I had to bear in order to have the great auto sensing feature of the wipers, also one of MY favorites!

 

Thanks, guys! I knew I came to the right place.

 

I checked through the windshield like Brutal said to see if there are bubbles, and sure enough, it isn't well attached. I have the new disc. I managed to get the plastic covers off, but I can't figure out how to remove the mirror mount or anything else to get to the disc. I don't want to break anything experimenting. Any advice or instructions?

 

Gus shows how to remove the mirror here: JagRepair.com - Jaguar Repair Information Resource

 

I finished replacing the adhesive disc. Here is how I did this, not saying all of these steps are needed or correct, but just my steps.

First, I removed the lights/garage door buttons console. It just pulls almost straight down, starting at the front near the windshield first. Then disconnect the left and right electrical plugs. Note, When reinstalling, there is a plastic tab at the back (back means toward the back of the car), fit this in first, then push the unit up into place. Quite simple, just be aware of that plastic tab when removing.

Next, I removed the plastic cover that fits around the base of the mirror against the windshield. I am not sure this cover really needs to be removed, knowing what I know now, but not sure either way. This cover is two pieces. I just squeezed the top piece with my fingers on one side and thumb on the other and pulled up. Did the same for the bottom piece, but pulled down. It is not difficult to figure out. There are electrical connections in the bottom piece, I didn't unplug these.

Now what stumped me was how to get the mirror off of the mount. The mount is glued to the glass. It is about 1/4 inch thick. It is round. Imagine a circle and a clock face. The bottom half between 3 o'clock and 9 o'clock has a grove machined around the outer perimeter. The mirror base has a flat surface the size and shape that matches this mount, with a spring metal prong on each side again at 3 o'clock and 9 o'clock, and these prongs protrude an 1/8 of an inch further than the flat surface of the mirror base. These prongs fit into the grooves on the mount. Knowing this, it should be easy to imagine that the mirror unit just slides straight down at the same angle of the windshield. The spring prongs hold the mirror onto the mount and slide in the grove. Just gently slide the unit down, like I said, at the same angle as the windshield. It is tight, but will move. Be careful not to twist the mirror, just push down gently. Also, be sure to try to slide it at the same angle as the windshield, otherwise you could crack the windshield.

With the mirror removed, you will see the mount that is glued to the windshield. In the center of it there is the rain sensor. It is under this where the adhesive disc is located. The disc holds the sensor in place. At 12 o'clock is the electrical connector, which of course needs to be unplugged. I used a small flat blade screw driver under the area where the connector is located and gently/slowly preyed the sensor away from the windshield starting at the 12 o'clock position. I got it up enough to get my finger tip under enough to continue to pull the sensor away slowly, take your time and be gentle. Don't break the plastic where the electrical connector is. Once removed, the adhesive disc was left on the windshield, and was very stuck. I used the same small screw driver and slowly pulled it away from the windshield.

Once completely removed, I cleaned the glass where the pad was with rubbing alcohol.

Now, this is where I made a mistake. The new adhesive pad has a thin plastic sheet on each side to protect it during shipping. Mine had a red color plastic sheet, and yellow on the other side. I thought the red side seemed much stickier, and it seemed logical that the red should be applied to the windshield. But getting that red plastic off is not easy and I feared I would deform the shape of the disc, as the disc is a very pliable rubber like material - think of a gummy bear sitting in the sun for an hour and glue sprayed onto it. So, I peeled off the opposite side, stuck it to the back of the sensor, and then was able to peel the red plastic sheet off, and stuck the sensor onto the windshield. The trouble with this is that the area on the sensor where the disc is fitted is slightly recessed, so, there isn't much thickness left to the disc as it is applied to the windshield. This means that getting really solid adhesion to the windshield less likely, as you just can't put enough pressure on it. I looked at the disc from the top side and saw a couple of bubbles.

Fortunately, I bought 2 discs, they were very inexpensive. So I put the remaining new disc in the freezer, pulled the disc I just applied off the windshield and cleaned up the glass again. After a few mins in the freezer the disc was hardened enough so that I could peel the red plastic sheet off without deforming the shape. I also used scissors and cut the yellow plastic sheet around the disc. I was able to apply the disc to the windshield now and used my thumb to apply pressure ensuring good adhesion. But placing the disc is the exact correct location is tricky, it must be placed exactly right so that it fits into that recessed are on the sensor, and this all is inside that mount. Be careful not to push too hard though so as to not crack the windshield. I then used pliers to grab the yellow sheet off, applied the sensor, and reinstalled the mirror and covers.

 

Great writeup. Thanks! I'll be doing mine soon.