The original switches were Philmore 30-550 (red) and Philmore 30-552 (green)
Here you can see what it looks like in the A-car desplayed at the Petersen museum :
If you don’t want to cut up your original steering wheel center you can get this replica thas all the holes and storage place for the 9V battery in place
The switches on the steering wheel don’t seem to get much love in the Back to the Future movies.
As far as we could find they seem to appear only twice in the first movie. Once when Marty escapes from the Libians and once when he can’t start the car in 1955. I don’t think they were ever lit in any of the three movies but most time machine builders make them light up (using a 9V battery).
The center pad (Article 106397 EU & US) clicks out of the steering wheel with a little force.
Although it may seem simple to just cut 3 holes and put the switches in, it can get pretty crowded inside if you want to fit the 9V battery as well. That’s why we did this backplate that serves both as a cutting guide and as a lock to keep the switches in place and hold the battery.
Here’s a video illustrating how to mount it all :
