Maybe there's a Ford mechanic somewhere that can point me in the right
I have one of those graphic display modules that were popular in the
late eighties and early nineties in the console. When I use the right
turn signal, hazards or brakes the "brake light" led indicator lights
up, even though I have verified that the rear brake light is working.
The bulb is a dual element that is used as the tail lamp and the
brake/turn/stop lamp sharing a common ground. If the ground were bad I
think the "tail lamp" indicator would also light up on the graphic
display due to an interruption in the normal flow of electrons. I've
ruled that out.
The graphic display has "rh brake light ref" and a "rh brake light
sense" inputs. Not sure what these mean, but probably "reference" and
"sensor". I have verified with a test light that the "rh brake light
sense" input is getting the same signal as the hot wire going back to
the brake light. The signal originates in the multifunction switch on
the steering column. I don't think the "rh brake light sense" wire
should be getting this signal if the light is working.
Looking at the electrical schematic, there are two splices off of the
hot orange/blue wire going back to the tail lamp, one going to the "rh
brake light ref" input and the other going to the "rh brake light
sense" input on the graphic display. In between the two splices is
shown to be a "resistance wire" spec'd to be 0.248 ohms. How this
circuit is supposed to work is really a mystery to me.
Just wondering how these two splices and resistance wire work with the
brake light hot wire and graphic display inputs, or simply, how the
electrons are supposed to flow.
I pulled another graphic display from the junk yard and plugged it into
my car and the same symptoms appear.