LCM3 vs, LCM4

[Rev Engineer]

Here is a copy of the post I made to bimmerforums.com

I've made some progress on this. I purchased a new prism+adhesive from automotivedesigngroup.com. Cost was about $30 shipped. Despite the kit coming with some good installation tips, I was not able to apply it without getting bubbles. A waste of $30 bucks. Bummer!

I noticed that the adhesive that comes with the prism is 3M VHB clear tape. My local Home Depot sells a small roll of 1 inch wide VHB for $5.

3M 1 in. x 1.66 yds. Clear Mounting Tape-4010 at The Home Depot

1 inch wide is narrow compared to the width of the prism, but the opening on the glass silkscreen is only about 1 inch. So centering the tape on the prism should be good-enough.

The stuff is very hard to apply without getting bubbles! After 3 attempts, I still had a couple small bubbles, but I went ahead and tried it anyways. At first I still had an initialization with 255 readings, but after messing around it for awhile, I finally noticed some normal readings and the dang things appears to be working as spraying some water on the windshield activities the wipers.

I'm not sure how much the bubbles are affecting the performance, but without coming up with a new technique to apply it, I'm not confident I can even do it without bubbles! Fortunately, the little roll that Home Depot sells is long enough for several tries.

A few more notes.. The kit from automotivedesigngroup comes with a small capsule/applicator of 3M Primer 94. This is supposed to be used with the VHB tape with glass applications. However, the VHB tape is very sticky and I don't foresee the RLS sensor coming off the windshield without it. It was hard enough removing it when I was going through all my application attempts.

Rubbing alcohol works very well for loosening/cleaning the VHB for re-applications attempts.

The installations tips from automotivedesigngroup says to use indirect heat (like a light bulb) to help heat the adhesive to help it stick/flow. They suggest NOT using a heat gun as this might allow dust particles to stick to the VHB. Cleanliness is stressed. After dealing with air bubbles so many times, I gave up on caring about cleanliness.. So, I used a heat gun to heat it which seems like it might have helped with the bubbles.

Lastly, it would be great if someone could figure out a good way to apply it without bubbles. I have enough tape left over to try it a few more times, but I'll wait to see if anyone else cane figure out a good technique. It's easy to apply it to one surface without bubbles, but getting two surfaces stuck together without bubbles is hard..

As a side-note, the VHB tape is 20mil thick and is sort of like a gel. Very similar to the factory adhesive.