One of the annoying niggling issues I’ve had with my 380SEC is that the front interior dome light hasn’t been working properly. If I apply a little pressure to the switch when it’s in the On position or one of the doors is open it works OK, but that’s not how it’s supposed to be.
I was waiting in my car while picking my daughter up from an art class and decided right there, that I would pull it out and fix it. How hard could it be?
The first thing I did when I got home was remove the light fitting from the car and take inside for an inspection. There was nothing immediately obviously wrong with it, so I decided to pull it apart. I started by prying the rear reflector off on the side of the switch with a screwdriver and this gave me access to the circuit board. It wasn’t immeditately obvious how to remove the circuit board, but then I noticed that the electrical pins had a little push tab on them. I figured if I push on these tabs, I’d be able to remove the pins and then easily lift out the circuit board.
After I pulled the pins out, I was able to quite simply pull the rest of the electrical components out until I had a pile of parts in front of me. The first thing I noticed is how dirty the electrical terminals were, so I gave them a quick clean up with a bit of wet and dry sandpaper. After 40+ years of service it wasn’t looking too bad, but I wanted to make sure it would all work when I reassemble it.
After cleaning all of the terminals, it was time for reassembly. When I pulled it apart, there were a few components that fell out and I wasn’t exactly sure where they came from, but I figured they would fall into place by trial and error. At this point my daughter happened to find a tiny ball bearing on the floor in my immediate work area (the kitchen bench). I never noticed this falling out so it was lucky that my daughter spotted it. As for where it goes, well there was really only 1 place where it could “fit”, which was in the small hole in the plastic switch. There was also a tiny spring that I decided could only fit in that place, so I put the spring in the hole and the ball on top. I was pretty sure this would work as I couldn’t find any other obvious places for it to fit.
That was the easy bit, but I also had a copper flat-spring type component that I needed to fit and I couldn’t figure out where it went either. I took a bit of a guess trying to figure out where it went, but couldn’t quite get it to work. Then I noticed that there are 2 tiny slots in the circuit board that match up to the 2 little prongs on this spring. This had to be where it goes!
This location was further confirmed when I noticed that the part of the circuit board that makes contact with this flat spring had worn through the solder on the board. I took out the soldering iron and added a small clump to the 2 terminals. The flat spring was now able to make full contact with the terminals!
I put the flat-spring in place and then had to work out a way to combine the switch and circuit board so that I could put them back into the housing. Gravity wasn’t on my side as whatever I tried would either result in the flat-spring falling out of the ball bearing falling out. I got a little creative and took a small piece of blue tack on one of the prongs and used this to stabilise the flat spring. With this method the flat spring wasn’t susceptible to falling out and it would hold just strong enough to allow me to join the 2 components together. Once combined I removed the blue tack and placed the switch and circuit board together as a single unit into the housing.
From here It was simply a matter of pushing the terminal pins back in, including the 2 large terminals that hold the globe in place. I added the globe and pushed the rear reflector back down. It was back together as a single unit.
I did a quick test of the switch to make sure it moved as it was supposed to and found that adding those 2 clumps of solder to the board had an unexpected benefit. The switch is now firmly held in place and moves with a solid feeling click. Being over 40 years old, it had worn down a bit and felt a bit loose.
I reinstalled it in the car and … success! It works perfectly now. It lights up when I open a door and stays on for a few seconds after I shut the door. I forgot that it stays on for a few seconds after closing the door and thought I may have stuffed up! In the On position it lights up and stays on.
