(From my thread on xfalcon)...
So - the Process. 1. Get Diagnostic Panel out. No pictures of this part, but to summarise : a. put downward pressure on the panel cover, and pull out at the bottom. Then unclip the cover from the top. b. Undo the 3 screws holding the panel in. The Manual says these are torx, however mine were phillips. c. Remove the unit, and unplug the connector. 1a. if your going for a quick fix, simply bridge the two Green/Red stripe wires here with a quickcrimp. The brake light warning will come on when the brakes are on, however the brakes will work. 1b. Lets do the fix in the unit. 2. Undo the 5 screws holding the cover panel on and remove the cover panel 3. Undo the 2 screws holding the Switch frame on and remove the frame 4. Undo the two screws at the back where the connector is (no pic sorry) 5. Gently pull the assembly out. It may be quite tight. I used a screwdriver to gently lever the PCB stands (black plastic things) at each end. I also pushed gently at the connector. 6. The issue is this resistor load pack just above the connector. mine has a brown mark on it where it has failed. 7. There are two Large pads there that can be used to bridge the circuit. Clean the coating off the pad - I used a knife 8. Join the Pads. Ive used some solid 240v power cable here.... 9. Finished product. 9a. I didnt think to do this, however you should probably remove the brake Fail lamp. In this picture, its the top left lamp in the cluster of 5. Just remove the holder 10. Reassemble the unit. 11. Reinstall. 12. Enjoy working brake lights. Remember to rewire the trailer connector if you have one.