I am having some odd trouble with my brake light/blinkers/reverse lights and have searched this forum but haven’t found an answer to my exact problem.  This is on a 1985 BRAT GL 4spd non-turbo EA81 car.  The symptoms are as follows:

-Press brake pedal-  stop light lamp and RH turn indicator light up solid on dash.  The taillights and stoplights do illuminate but the reverse lights do as well with the brake applied. 

-When I remove the RH tail/stoplight bulb- the conflict goes away and everything works as it should (with the exception of the bulb that was removed)

-Also, when I turn on the emergency flashers, nothing happens.  No lights on dash or on exterior and no clicking from the flasher module. 

-Both turn signals function normally when I move the blinker switch to either side (which leads me to believe that the flasher module is good).

Could the flasher module still be faulty despite it working properly with the turn signals?  Any help is greatly appreciated!

Check the grounds on the lights.

I checked all the grounds on the sockets as well as the ground in the right rear panel in the bed.  All good.

Inspected the 2 connectors that connect the rear harness in the FWD bed panel on the RH side.  The connector was crumbling apart so I took each wire and spliced them individually with no change in symptoms.  Inspected all the wiring under the dash and it all looks fine visually.  Disconnected the steering column blinker switch and the turn light indicator still lights up with the brake pedal.  disconnected the black flasher module and this also did not affect the brake light/turn signal relationship.  

Sounds like someone had modified the wiring some time ago, or you have wire damage from rats etc. 

You’d be best to trace ALL wiring from the back of your brat to the front to find out where the issue is. It sounds like someone had tapped a power wire for the indicator and reverse light from the brake light. This circuit is broke when the globe is removed. This had me thinking the issue can’t be too far away from the tail light. 

Got a trailer plug fitted? Look into this too as it could be the source of the issue, not uncommon for someone to bugger that job up. 

Cheers 

Bennie

i like the mud/moisture in trailer socket theory. I also seen if the filament has broken at one end, fallen across the other in a dual filament bulb you get all sorts of crazy stuff. I also found after my own fiddling with radio and other things, similar weird problems. I fixed it only by installing those blue diodes you sometimes find in the wiring looms. Used about five or six in total before fixed.