How do I change the third brake light bulb. The inside trim cover looks like it comes off but I do not want to damage it not knowing where the fasteners are.

pry the plastic trim off from inside the back window.

If some of the lights work then you probably don't need to change the light assembly. My first guess would be a burnt out fuse. Look for the fuse box and remove the cover. Usually on the inside of the cover it will have a diagram for all the fuses and you can find the one for the brake lights. Some vehicles have relays that are fried and these may be under the hood. Just look for a black box which contains electrical relays and other fuses. The last thing I can think of is a switch that is right above the brake pedal. When you apply the brake a small plastic or metal extends and this is what makes your brake light come on. www.lightdeal.co.uk

You have to remove the trim panel from the lift gate to get to them.

some of these are done from the trunk, open trunk and look for socket if its closed in then just go inside car and gentle pry rear cover off third brake light housing, once cover is off you can change bulb and more more required then remove housing.

If you do not know what you are doing you should go to a mechanic. A simple slip with a screw driver can cost a lot of money.

Trace the wiring as it comes from the laft and right brake light. May have to remove the brake light covers. Sounds like a crimped or shorted wire leading to the brake lights, possibly a loose or broken ground wire. One of the wires leading from the fuse block to the rear oif the vehicle could also have been damaged if the door sills have been removed by someone earlier to install things like speaker wires, etc. Also check to see if you have tail lights and directional signals.

When you replaced the bulbs did you get bulbs with double filiments - one acts as the tail lights, the other serves as the brake lights (both inside the same bulb). Compare the ID numbers on the bulbs with those which are required for this vehicle, but you should clearly see two different filiments inside of the bulbs when viewed from the side.

Look on the inside of the liftgate and you'll spot a plastic trim panel/piece directly behind the High Mount brake light. Gently pry this piece off and you'll have access to the bulb and socket.

open the trunk and look up along the top of the bumper and you should see two screws / nuts that secure the light assembly.

3 clips total. 2 on outside of light unit, to get to these you have to remove central trim from over boot latch, side trims and carpets, toolkit out, seats folded down, luggage blind removed, small trim piece inside wheel well removed (2 bolts 1 nut), then you can get up behind the light unit, gently clip the 2 outside (red) clips out till the light unit becomes free. to get to the third there is a black plastic trim piece clipped to the light unit where the boot comes down and meets it, this covers the third clip, gently pop it off and you will reveal the third clip and the nut needed to be removed to release it.

The trim inside your car behind the light removes after taking some clips out with a flat head screw driver, then you can get to the bulb harness and bulb