US-spec 308 GT4 Door Switch Grounding

Does anyone know how this was grounded from the factory?

A friend and I spent HOURS trying to figure out an electrical issue on my 1975 Dino 308 GT4. The problem was the two interior door lights and dome light did not work. These are the lights that should come on when you open the door, and turn off when closed (and they can also be set to “always on” or “always off”). They didn’t work no matter how they were set.

Long story short, it turned out to be a grounding issue with the switches. For a US-spec car there’s two switches on the left side, and one on the right. That switch needs to be grounded on both sides in order for the lights to work as expected. However, those switches mount in a decorative body panel made of plastic, so they can’t be grounded to the body the way a normal car would be.

Image Unavailable, Please Login

We didn’t have the energy or time to remove the doors to get behind the panel and create a proper unseen ground, so for the mean time we created a ground that connects to the screw above the switch. It was the best we could do given we didn't expect a body panel to be made of plastic, and we made it as elegant as possible by cutting a cable to the correct length and tucking it under the weather strip. It solved the problem as all the lights work now, but obviously it didn’t look this way from the factory.

Image Unavailable, Please Login

How was this grounded from the factory? If we had removed the doors and set this ground wire up BEHIND the decorative plastic panels, then it would be completely invisible and look factory. But, if/when I ever need to remove one of the switches, then having this behind the decorative plastic panel would cause a problem (I wouldn’t be able to reconnect it without removing the doors). Additionally, I don’t see anything in the parts or workshop manual that indicate additional wiring or anything in the area of the switches. Is this cable the switch connects to grounded somewhere else? I haven’t been able to dive that deep into this yet.

 

Interesting that mine are plastic (or maybe just unbelievably thin metal that sounds like plastic?). I am happy to hear the panel can be removed without taking the doors off, so I'll give that a shot the next time I'm able. But, if it's plastic, so I'm not going to achieve a ground through that panel so I'll have to ground to the body or something.

Switches are readily available and relatively cheap too, but aren't needed as we have thoroughly cleaned and tested them and found no faults. But, may replace them anyway, it's not like it would hurt anything.