Hi,
I have a problem with the drivers side brake light...
When the pedal is depressed the brake light does not come on, both the passenger side and above the rear window come on.
However if a friend was to depress the pedal while I try and adjust the unit that holds the bulbs the brake light comes on...I only have to loosen the unit by 1 inch and it comes on.
It would appear that there's a wiring/short issue but I dont know how to detect it.

Please could you help?