Our 2007 Dodge Caliber had a taillight that would get foggy looking. We could see water on the inside of the taillight, that couldn't be good for the electrical connectors. I took the light out once (two black plastics "screws" inside the trunk area -then remove the three bulbs from their sockets), emptied it, dried it and looked for cracks. I couldn't find any, so I put it back int the car.
Same problem of condensation inside the lens, after the next rain. I figured I had little to loose if I caulked the taillight.
First, I made the assembly was fully dry. I used a hair dryer through the bulb holes to get all the condensation out of the taillight. I used 100% silicone bathroom caulk. A good quality sealant, that could be used to seal much tougher things.
Here is the taillight removed (shown from the back side). See the two tabs where the screws held it in.
Start a silicone bead in the upper part of the Caliber taillight assembly. I filled the channel completely, between the read lens and the black plastic back assembly.
Continue sealing around the whole outside of the tail light lens assembly.
Work around the outside putting a thin bead silicone between the red and black plastic tail light lens parts.
Just use your finger to smooth it out. I let it dry overnight and then put the taillights back on the Dodge Caliber. This saved the expensive prospect of replacing an otherwise good taillight, due to some hairline crack that wasn't even visible to the human eye.
If you see water in your Caliber's taillight, hopefully you can just drain it, dry it, and seal it like I did.
I used 100% DAP clear silicone caulk to seal my tail light assembly. It's been 6 months since I did this and the Dodge Caliber's tail light assembly hasn't been foggy or had any water in it since.