Deconstructing 2CV dashboard indicator lights

I have been looking into the feasibility of adding main beam and indicator instrument lights to the dashboard of Judith.  These lights weren’t fitted to the Spécial but the wiring is still present in the loom as they were standard on the Club dashboard.  As the 10mm diameter holes are already present in the dashboard it’s relatively simple to add after-market indicator lamps but, as the 2CV’s indicator light bezels are quite distinctive, I wanted something more in keeping with the originals.

One option would be to try and get hold of the blue and green lights from a club dashboard and fit those.  However, these aren’t that common so I am investigating the use of LEDs whilst retaining the characteristic bezels.  In order to find the right LEDs and fittings I deconstructed an original dashboard indicator from a “spares or repair” 2CV dashboard acquired via a well known internet auction site.

The indicator light consists of three parts: the bezel, the bulb holder tube and the bulb assembly .

2CV instrument light components

The bezel fits through the hole in the dash and screws into the holder tube.

2CV instrument light holder

The bulb assembly is a push fit into the rear of the tube and shines through the coloured “glass” (actually plastic) in the bezel.

My plan is to replace the glass in the bezel with an LED.  This will keep the distinctive look of the 2CV’s dashboard lights, be easier on the alternator and hopefully be more reliable

With the bezel removed it still wasn’t clear how the glass was fitted, there was no obvious way to remove it leading me to conclude it was molded in.  Unfortunately the best way to determine this was to saw it in half with a fine toothed modeling saw.

2CV instrument light cross section

With the cross section revealed my suspicions were confirmed – the glass is indeed molded into the bezel.  However, there is only a thin ring of the outer plastic holding it in place at the back and, with this removed, it is possible to push the glass out from the front.

2CV instrument light glass and bezel

With the light now fully dissembled I was able to get the vernier callipers out and document the details of the key parts.

(Drawings are not to scale.)

Light bezel

2CV instrument light bezel

The light bezel holds the glass in via the shoulder allowing the dome to protrude.  The key dimension is the 6mm hole through which the glass fits.  The countersink on the face is approximately 1mm deep.

Light glass

2CV instrument light glass

The light glass is what’s going to be replaced by the LED.  It protrudes thorough the bottom of the bezel’s countersink by 2mm.

Light holder

2CV instrument light bulb holder

The holder acts as the nut on the rear of the dashboard and is quite deep to allow for the bulb and fittings.  The bulb assembly is held in via a friction fit that is secured by a steel ring that slides down the taper to compress the base.

Bulb assembly

2CV dashboard indicator light bulb assembly

The key dimensions of the bulb assembly are the 14.5mm width of the body for the friction fit and 6.5mm for the spade connector.

Other posts in this series

  1. Deconstructing 2CV dashboard indicator lights
  2. 2CV dashboard indicator LED lights proof of concept
  3. 2CV dashboard indicator LED lights prototype
  4. 2CV dashboard indicator LED lights
  5. 2CV dashboard indicator LED lights – fitting