2012 Volvo S60 third brake light help!! | SwedeSpeed

Just to follow up this post, since it was a top hit on Google – had the exact same issue, the root cause was cracked solder joint on one of the two terminals where the power plugs into the circuit board for the brake light module.

To identify, I hooked up a little 12v test lead (using some spare socket pins and breakout wires) to the module and observed it flickering on and off when the wires were moved. Note that the centremost wire is positive and outside is negative – in the picture below, that’s right side is positive, left side is negative. There’s no protection diode so don’t get it wrong. If unsure, the board itself has positive marked.

The board is held in place by 5 clips, the plug itself and two each side in the outermost cutouts, top and bottom. Remove the board and clear diffuser from the black plastic holder, then remove the black plastic plug from the board (it just slides off once unclipped). Once you have access, resolder the two pins. You will likely need to remove the old solder and use fresh to get a good connection. See linked photos. Photo of the board is before repair, showing the dried and cracked solder joint.

Obviously you will also need to know how to drop the headliner down, I recommend undoing both the front and back handles to stop it creasing behind the front handles. The C pillar curtain airbag covers will also need to be removed and an earth lead disconnect from the left side – it is taped to a clip I couldn’t remove, so I cut the tape and then zip ties afterwards.

The 3 rectangular clips at the back below the light itself need to be rotated 90 degrees to disconnect – the rear two hold the liner and light to the roof, the middle the light to the liner.

Once the liner is dropped down, the brake light can be unplugged by reaching up from the left-hand side and pressing the little tab on the headliner side upwards – the cable itself is glued to the headliner so you can’t easily pull it down otherwise.

Here’s a few photos to help understand how the light is unclipped from the headliner.