Can anyone suggest an easy way to trouble shoot the 3rd brakelight. It seems to not work, the other brake lights work. I assume it is disconnected since the tint job, where is the best place to check, under the trunk liner or take apart the assembly inside the car ?? It is LED so it burning out it not likely....I dont like to take it in to dealer unless necessary...TIA

 

There are two ways to approach it:

1) Take off the rear deck trim and access the brake lamp wiring there.
2) Pull back the rear quarter trim and access it from underneath.

You may want to take a voltmeter and check to see if it's getting any juice or not. There may be a possibility that the tint shop didn't take the extra step to cover up the unit when they were spray soaking the film with solution.