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That certainly looks like a factory-fitted plug, but it's not the 3-pin type I'm used seeing to on Mk1s. What year is the car?
The type on my '93 car has 3 wires; a pair of chunky wires for power, red and black, and a thin violet wire. When a demister is plugged in (either a hard top or glass windowed soft top) the purple wire gets linked to the black (ground) wire, and of course the red and the black get linked to the two terminals on the window element.
The purple wire runs forward to the dash, to the demister switch. Now that it's grounded at the rear shelf, that allows the switch to ground a wire coming from the coil of a power relay in the boot (under the trim panel below the boot latch). That switches on the relay and supplies power to the red wire on the rear shelf.
I was told many years ago some cars have a yellow wire instead of violet but I haven't seen one.
What wire colours do you have on that 4-pin?
The type on my '93 car has 3 wires; a pair of chunky wires for power, red and black, and a thin violet wire. When a demister is plugged in (either a hard top or glass windowed soft top) the purple wire gets linked to the black (ground) wire, and of course the red and the black get linked to the two terminals on the window element.
The purple wire runs forward to the dash, to the demister switch. Now that it's grounded at the rear shelf, that allows the switch to ground a wire coming from the coil of a power relay in the boot (under the trim panel below the boot latch). That switches on the relay and supplies power to the red wire on the rear shelf.
I was told many years ago some cars have a yellow wire instead of violet but I haven't seen one.
What wire colours do you have on that 4-pin?
