This relay/switch/??? is mounted on the rear cab panel of my '85 Brat. It's near the floor at the drive shaft tunnel area and is normally hidden by the interior plastic trim panel.

 

What is it?

 

That looks like the stop light checker - perhaps they moved them there in '85.... I could swear they were behind a panel in the bed though. Anyway it looks very much like it.

 

GD

Yep, it's the Stop lamp Checker Relay. Both BRATs I've had the trim panel off of had the relay there, an '82 and an '86.

Mine didn't have that there. But I'm in Australia and mine was an 89.