Cleaning GPS Signal Receiver Rubber Seal on Mercedes R129

On our Mercedes R129, the third brake light isn't the only spot in the boot lid where a failing seal can result in water ingress. It is fitted with a satnav, meaning the boot lid also houses the GPS signal receiver:

Every time we opened the boot after rain there would be some droplets of water rolling down from underneath the signal receiver, so we were wondering if it was contributing to the water problem as well.

To remove the GPS signal receiver, you need to take off the boot lid liner. If not sure how, I have described it in this post. Once the boot lid liner has been removed, what we saw was this:

Not entirely sure that this is how it looked fresh out of the factory - this looks like one of the previous R129 owners may have already tried to gain access by all means possible. You can see that it is held in place by one screw. Be very careful when unscrewing it and don't pull it out too hard, as there are several tiny sealing rings on it and they can fly all over the place - good luck finding and gathering them together if it happens. Once the screw is out, carefully wiggle the GPS signal receiver free. The cable is quite long, so there is no need to unplug it:

Amazing how much dirt can get underneath! We washed it off and applied some Carlube Silicone on the rubber seal to protect it. It's cheap, just a couple of pounds and does a great job on the rubber bits in the R129. The seal was quite hard, but rubbing in the silicone made it nice and bendy again.

Now reattach carefully and you're done!