When I bought my SD1, a number of the pushbutton switches on the dashboard weren't working. They made contact, but they would not stay in the 'on' position. Being the penny-pincher that I am (the more money I can spend on petrol, the better ), I thought I'd try repairing them rather than replacing them, and discovered a sure-fire way to get the switches working again. I'm not sure if the Series 1 switches can be repaired in the same way, but this method works for all the push on/push off switches in the Series 2.

First, remove the switch from the dashboard by disconnecting the battery, removing the binnacle cover, disconnecting the switch's plug (in my car all the plugs were keyed so you can't reconnect it to the wrong plug) and gently pressing on the back of the switch - it should pop out of the front of the instrument panel.

Next, we're going to open the switch up. Since the switch contains several small spring-loaded bits, it pays to do this inside an icecream tub or similar, to catch all the little flying bits and pieces. The base of the switch is held in place by two clips, one on each side. Insert a flat-head screwdriver into each clip and pop it open. Pull the base of the switch off and a few bits and pieces should drop out - two flat bits of metal (these are what hold the switch in the dashboard) and a small spring. The switch should be in two pieces now: the switch body (the big bit with wires coming off it) and the base (the little flat-ish bit).

The way these switches work is that the spring sits in the base, held down with a small plastic tab. A small bit of the spring points up into the switch mechanism, and runs in a track that provides the push on/push off action. What had happened in my case was that the tab had broken, allowing the spring to come adrift. The switches still worked, but they wouldn't stay in the 'on' position.

After a lot of trial and error, I have found a way to hold the spring down and make it all work again. Place the spring in position and hold it there with a bit of blu-tac or tape or something. Cut out a square of thin plastic, about 1cm × 1cm, and glue it over the coiled part of the spring, being careful not to get glue on the spring itself. Let the glue cure, remove whatever you were holding the spring down with and so long as you put everything together correctly and the plastic is thin enough, the switch should go back together just fine. Just remember to put the clips back in - they are held in small slots in the switch body and base.
I did this to three switches in my car, and all of them have held together and work perfectly, and so long as the glue holds, they should work for the forseeable future.

Pictures will come as soon as I can find a spare switch to dismember.