anyone seen this:
lights on and apply the brakes the left brake light does not light and the tail light goes off (that part may be normal). the light bulb is good of course

 

I just fixed something similar yesterday. Running lights would not work, and brake lights didn’t work when headlights on or when in reverse. Turned out to be water in tail light causing corrosion, cleaned it all up and all lights work correctly. Not sure about just one side failing but it could be something corroded in the tail lamp assembly as all of those lights share a ground wire. For my issue both sides had the same problems, but only the right rear light assembly was corroded.

 

turned to be a flakey connection between the bulb and the fixture

 

Not to hijack this thread, but I have a vaguely similar condition, with left and right brake lights behaving differently, and it's not a bad bulb.

Will look for and attempt to remove any corrosion or similar issues, and see if that fixes it.

 

Inside the back hatch area of your Disco 2 on the passenger side is a plastic vented cover on the corner vertical pillar.

Pop it out and look inside.

I had a small electronics box in there that had a ground screw holding it on to the frame, except that it had come loose. I got really odd behavior from my taillights and brake lights until I found and screwed that ground screw back tightly onto that box.

 

Studying the problem more closely, I see evidence of some wiring work having been done on this light before. I suspect the two live wires leading to the bulb (not the ground wire) may have been reversed. Will check this out.

 

here is what im seeing....

(WORKING running light) REAR RIGHT PLUG with headlights and ignition on:

BLACK TO PURPLE GREEN = 0 v
BLACK TO WHITE GREEN = 0.1 V
BLACK TO RED ORANGE = 13v

(NON WORKING running light) REAR LEFT PLUG

B TO PG = 0v
B to RG = 0.6v
B to Black Red = .6v


maybe a short to ground? or is there some other reason im not seeing?