This is a selection of vintage SAAB instrument panel rheostats, which don't look too bad but....they refuse to work.Some refuse to rotate, some only work on full bright, but with most of them, they will rotate but nothing happens.
This drawing shows all the gubbins inside one of these little buggers. HEAT from the resistive coil of wire is the problem. It causes a really nasty build-up of crud on the brass contacts and no amount of squirting ANY commercial cleaner in there will blast off that build-up. I use some REALLY nasty stuff and some special cleaning tools to convince Mr Rheostat to do its thing once more.
This is a typical rheostat once it is dismantled. The resistive spring in this one is shot, which probably means it is a parts donor unit.
Below are three rebuilt rheostats, ready to happily dim the instrument lights in someone's Saab for another 40 or so years.
This photo--and the drawing--show a couple of different knobs. The short knobs are for early cars, the long knob came into use around 1970. I'm sure you will be pleased to know that the rheostat doesn't care what knob it has on it.
City Car Design
6 years ago