I know a lot of people who have had condensation/water in the rear bumper light clusters.
Here is a solution that I have now tried on my 3.2GT. Apologies to those who have tried this already. These lights are in direct line of the rear wheels and have unprotected electrics which can give odd faults like 'rear lights not working' or 'bulb failure', when in fact the connections are just wet. Hardly surprising really and a bad design asking for trouble. Personally I hate looking at misted lamps, which will happen when only the slightest drop of moisture gets in.
Here is a 'cure', but I hesitate to use the word!
First my bumper was removed for painting after a buffoon drove into me. So I took the opportunity to remove the light clusters. Unplug the wires - we'll return to this.
You can't open the lights up. Clean up as best you can to remove grime and polish the glass, remove the rubber plug carefully at the opposite end to the bulb. It does nothing and is used to blank off a hole that might have been used for another bulb. You may find water behind it anyway, I did! Then leave to dry near a radiator for several days (yes really). If you can't wait use a hair dryer down the bulb holes and all over the glass - especially around the edges where you will see tiny moisture bubbles. Its essential you are sure there is no moisture left because otherwise you will seal it in
Be persistent and very sure there is nothing left because mist will come back to
haunt you otherwise. Then squeeze glass seal silicon into the unused bulb hole and around the old rubber plug and replace. It will seal. Then very carefully seal the bonded edge seam around the glass (plastic) filling the groove and overlapping by just 2mm or so. No more because it will show when you refit if its all over the place. Use masking tape and a craft knife to get a steady line and clean off carefully when wet. Its silicon so repels waters if used properly. Bit sticky though.
Let it dry off properly and refit into bumper. Another reason not to use too much is because you don't want to make it difficult to remove the lights if you have to paint the bumper anytime.
Squeeze a little silicon sealant into the outer ends of the electric plugs around the wires before fitting, but be tidy. That prevents water going into it. Also refit electrics into the plug housing using grease around the sides to prevent water going down the sides of the plastic plug. Don't put anything on the connections themselves or you'll lose continuity! Yes I know its obvious.
One word of advice - don't overdue the sealant, 'cos its very sticky stuff - and be careful when handling the lights 'cos the brackets are not strong. GOOD LUCK.
So far so good - will let you know if it holds up. But I have clear light at last.