850 interior dome light switch repair

[gdog]

Apparently this is a pretty common failure, but this is first time I've seen it.  The center toggle switch on my interior dome light exploded and now dome lights don't work at all.  This is the switch on interior ceiling just back from the interior mirror and ahead of the sunroof.

 

Went searching for new switch but too expensive!  I think this is P/N: 9483142

https://www.eeuroparts.com/Parts/9871/Dome-Light-9178823/

Used ones are long shot at this point since they're probably broken (or close to it) now too.

Pulled up the schematic to see what I could do. 

This is a MODE switch; per the owner's manual, it has 3 modes:

1. Interior dome lights always off (center position)
2. Interior dome lights always on
3. Interior dome lights switched via door switches

Since the only mode I've ever used is mode 3, I decided to attempt to hard-wire it for that mode.  Mode 1 is useful if you're going to have the doors open for an extended period of time, but I figured I can always disconnect the switch if that need arises.

Pulling the interior dome light switch is simple, but watch Robert's video if you need refresher: https://youtu.be/KFz7rvEIFXY?t=418

After staring at the schematic for awhile, figured out how to hard wire mode 3:

1. Tie switch pin 2 to 3
2. Tie switch pin 5 to 7

I did this by soldering jumpers onto the pin buses; you'll need to scrape off the anti-corrosion coating in a small spot to get to the copper underneath for solder to stick. 

With the jumpers installed, it works great! 

Note this maintains the Delayed Courtesy Light function when you shut the doors.  I.e. the dome lights stay on for about 20-30 seconds after you shut all the doors, and then fade to off.  They will go out sooner if you key to RUN position.

Hope this helps someone.

Let me know if you need more pics.