2CV dashboard indicator lights – version 2

With the green indicator LED having failed at a weak point I had to make up a new one and address the weak point.

The wires that came attached to the LED were very thin and the crimp point of the connector had focused the stress of any movement onto a single point.

To provide additional reinforcement at this point I covered the wires with two layers of shrink wrap before crimping the connectors and soldering the wires.

Green LED with extra shrink wrap

The resulting assembly was much more robust and survived fitting with no issues.

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

2CV dashboard indicator LED lights – fitting

With the LED dashboard lights made up they could be fitted into the dash. With incandescent bulbs the polarity of the connectors isn’t important but with LEDs the current will only flow one way to light them up and connecting them in reverse could cause them to burn out.

The Haynes Manual does have the Citroën wiring diagram which lists colours for the indicator light connectors and/or wires. Using that as a starting point and cross checking with a multimeter I came up with the following list of connectors:

  • Oil pressure warning (red)
    • Live: purple connector, green wire
    • Earth: white connector, green wire
  • Hazard warning (red)
    • Live: white connector, brown wire
    • Earth: brown connector, green wire
  • Brake fluid warning (red)
    • Live: red connector, brown wire
    • Earth: purple connector, grey wire
  • Main beam (blue)
    • Live: blue connector, green wire
    • Earth: brown connector, green wire
  • Turn signal (green)
    • Live: green connector, green wire
    • Earth: brown connector, green wire
  • Fog light (orange)
    • Live: white connector, green wire
    • Earth: brown connector, brown wire

A quick test with the dash off showed they were all working as expected.

With the lights in place the dash was harder to fit back as the wires for the right hand side previously passed through the space now occupied by the indicator light. After a bit of sorting out the cable routing the dash was fully reassembled ready for a test.

All was looking good until I got to the indicator light which didn’t light up.  After taking the dash off again the problem was obvious: the thin wire on the LED had failed at the crimp point of the connector.  Whilst disappointing, this was something I had thought might be a weak point so made up a better version.

With everything in place the lights did look the way I’d intended, they are slightly different to the originals but using the original bezels means they do look appropriate for the car.

2CV LED dashboard indicator lights in place

I’ve only tested them in daylight so far but I have a feeling they may prove a bit too bright for night time use.

2CV LED dashboard lights in action

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

2CV dashboard indicator LED lights

With the prototype LED dashboard indicator light finalised I started on making the full set of finished items.

It was a very small scale production line:

  1. Remove light glasses from the bezels
  2. Cut the PVC grommets
  3. Cut the rubber bungs
  4. Cut the LED wires to length
  5. Attach the crimp connectors and colour the negative terminals
  6. Solder the wires to the connectors
  7. Test the electrical connections
  8. Fit the LED, grommet and bung into the bezels
  9. Attach the light tubes

Assembly line of 2CV dashboard indicator LEDs

With each of these complete and tested I now have a full set of LED dashboard indicator lights ready to fit.

2CV dashboard indicator LEDs assembled

Full set of completed 2CV dashboard indicator LEDs

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

2CV dashboard indicator LED lights – prototype

When fitting the proof of concept LED dashboard indicator light I had found the 7mm PVC tubing wasn’t a firm enough fit to hold the LED in place in the bezel.  I found some 5mm ID – 8mm OD tubing advertised an bought a short length.

When the tubing arrived it was immediately obvious that the 8mm OD claim was somewhat of an underestimate: it actually measured 9.5mm.

By cutting a section out of the circumference of the tube I was able to reduce the outside diameter to fir the bezel.  However, this also reduced the inside diameter by the same amount and, as this had started at 5mm, it meant that there wasn’t room for the LED.

At this point a plan B presented itself:  I could use this larger tubing as a stopper behind the LED to prevent it pulling out.  After some experimentation I found that cutting a V shaped notch in the tube would effectively create a tapered grommet.

2CV dashboard indicator LED with rubber grommets

The compressibility of the rubber combined with the taper created a very effective seal behind the LED.

2CV dashboard indicaotr LED and bezel assembly

With the light in place I trimmed down the leads to the right size for the light barrels and attached some male spade connectors.  Due to the thin wire used for the LEDs there wasn’t much for the crimp connectors to grip so I used the crimp to hold the insulation and soldered the bare wire to the connector blades.

A side-by-side comparison with the originals shows they look very similar and should fit into the dashboard with no issues.

Front comparison of original and LED 2CV dashboard indicator LEDs

Side comparison of original and LED 2CV dashboard indicator LEDs

When doing a test with a battery the colour of the connectors became an issue.  The insulating sleeves are red plastic (denoting the size of the connector) so the only indication of the polarity was the wire that by now was mostly hidden in the light barrel.  Given the polarity of a diode is what makes it functional I coloured in the negative connector with a permanent marker to make fitting easier.

Testing a completed 2CV dashboard indicator LED

The final prototype was now complete and consisted of an LED crimped and soldered to two spade connectors, a 7mm clear PVC grommet and a C shaped rubber grommet.

2CV dashboard indicator LED parts

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

(Better) LED testing

Although my previous solution for testing LEDs basically worked, I wouldn’t go any further than that.

Because this will need testing more as I work on fitting the lights I came up with a better solution.  This uses a USB plug and some properly attached female spade connectors.

USB plug with female spade connectors

This means I can now use a USB power pack as a source of juice and it has an interface that mirrors the wiring loom in the car.  Admittedly the car runs on 12v rather than the 5v of USB but, whilst it won’t power the old incandescent bulbs, it is sufficient to light an LED.

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

2CV dashboard indicator LED lights – proof of concept

Having gathered the information about the dashboard lights and the LEDs I acquired some 5mm ID – 7mm OD clear PVC tubing to try mounting the LEDs in the bezels.

2CV LED dashboard indicator light bezel

A short length of this was enough to fit into the bezel and present the LED in the correct position.  Whilst not identical, the appearance is very similar and pretty much what I was aiming for.

2CV dashboard indicatgor lights - LED and original

With this basic version made up I then took it down to Judth to see how it would look and work in-situ.  For this test I wired it into the main beam indicator connectors so it was easier to control.

Comparing it to the oil pressure warning light it is noticeably brighter but, given the originals aren’t particularly bright to start with, that’s no bad thing.

Animation of LED and original 2CV dashboard indicator lights

A close up inspection shows they are visually different to the originals but, when there’s a full set, it’s going to be hard for all but the most eagle eyed to notice the difference.

One thing that was obvious when attempting to fit them into the dash is that the 7mm tubing isn’t anywhere near good enough of a friction fit to hold the LEDs in place so I’m going to try some 5mm ID – 8mm OD tubing.

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

LED information

With the dashboard lights deconstructed I started looking for appropriate LEDs to use.

The following are required:

  • Oil pressure high (red)
  • Brake fluid low (red)
  • Hazard warning lights (red)
  • Fog light (orange)
  • Main beam (blue)
  • Indicators (green)

To get as close as possible to the appearance of the light glass coloured diffuse LEDs are needed – these are the ones where the whole LED is translucent and coloured rather than being fully transparent with the colour coming from the semiconductor material used in manufacture.

From what I could find, diffuse LEDs in the colours needed come in 3mm, 5mm and 10mm sizes and were available with resistors suitable for 12V attached.  Given the inside diameter of the light bezel is 8mm and the hole for the glass is 6mm I elected for 5mm.

LEDs and 2CV dashboard indicator light

As the LED is undersized for the light bezel some from of adaptor will be required.  This would ideally be a tube that has an inside diameter of 5mm and an outside diameter of 7.5mm.

LED dimensions

5mm LED

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

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