New LED dashboard pilot/indicator lamps

[John Gervais]

Thought I'd turn y'all on to my latest project, changing the switched accessory incandescent pilot/indicator lamps on my auxiliary gauge panel to LED's.

What started as a pretty straight forward job naturally developed into a full-blown project, a lot of wiring in a small box, with all sorts of little pop-up challenges.  The gauge panel consists of a vacuum guage, tachometer and air/fuel meter, switches (APEM 3500 series) for fuel pump, rear fog lamp, driving lights, front fog lights and electric fan, as well as indicator lamps for when the switches are 'on'.  Not a problem for the fuel pump (green), driving lights (blue), and electric fan (yellow), but was an issue in that the rear fog lamp and front fog lights were sharing the same indicator lamp (red).

Although the driving lights and front fog lights are operable when the respective high or low beams are selected, the rear fog lamp can be operated with only the parking lights, or with both the low and high beams.  This common-shared dashboard indicator lamp enabled the high beam headlights and driving lights to be turned on if the parking lights were 'on' and both front fog and driving light switches were turned 'on'.  Funky. 

I decided to do something about it.  Should be easy enough to rectify, drill a hole and add a wire.  Go from having 4 pilot lamps to having 5, one for each switch.  Well...  So, out came the gauge panel, removed the gauges, lamps and switches.  Measuring twice and drilling once, I forgot to remove half the diameter (aka. 'the radius') of the new LED to the edge of the metal box, so the resulting hole was drilled perilously close the the vacuum gauge bezel.  Oh, well, can't really do much about it, and the gauge clears the LED. 

So, a bit about the LED's I found.  Wow, they're nice; I wanted something of quality, that would compliment the Smiths gauge bezels, and would be small enough to be 'tasteful'.

After an intense LED search, I found that Holden Vintage and Classic offers a 12mm environmentally sealed LED, which is quite large, and I also noted that they recommend adding an in-line resistor to the '+' side of the blue LED, as it's quite bright.  Ok, fine, I'll order a few resistors, and try to find smaller LED's.  Looking on the APEM website, found the APEM Q8-Series, which is available in 3 different bezel styles as well as wiring styles.  Sweet!  I decided on 2.8mm solderable lugs which are also suitable for crimped connectors.  A chromed recessed bezel gives that classic 'Smiths' look.

Aside from that the old incandescent lamps were 9½ mm diameter and the new LED's are 8mm, I figured I'd use a rubber grommet to sleeve the hole.  This worked just fine, and I used a 'modified' wire terminal ring connector (8mm hole with the 'crimp' section trimmed off - which essentially became a brass washer with an 8mm hole) as a hard surface for the spring washer and nut to clamp against.

A call to Vehicle Wiring Products for a bag o'2.8mm terminals and insulation boots, and an order to DigiKey for the LED's.

Job done, everything works as intended and the style is really nice.  I'd thought of going with the black bezels (moré sporté), but the chrome looks good with the chrome Smiths bezels.  If I change the Smiths bezels to black, then I'll change the LED's to match.

Next week, a package arrives with several GLB987-style 10-lumen concave glass LED's for the vacuum, speedometer and oil pressure gauges and a couple of festoon-type for the number plate/interiour lights from Classic Car LED's.  I recon the 10-lumen LED replacements will be similar in effect to a 5½-ish watt incandescent bulb - not too bright, but brighter than the originals.  T'was tempted to go with their 48-lumen, but this might be too much.  So we'll see, éh?


I wish I'd brought my camera to the garage and taken a few pictures.  I'll try to do so in the near future.  I'm really diggin' the effect.