Replacing a rocker switch light bulb

 TL;DR how to replace a light bulb, part II - keep incandescent bulbs

Not unlike the time the speedometer bulb died just after fiddling in the vicinity, the bulb of the windscreen washers switch failed right after routing the wires for the ECU drive mode too close to it. That was again just a happy coincidence, the power supply to the bulb connectors was all fine. The filament just burned out.

Duckduckgo led me to this 12 years old post, after what the trail of the "BU15 LES lamp 14V" finally gave me the "E5" socket, and the fact that 14V 0.7 Watts was what I needed for those Rover-looking rocker switches. It looks like a good search prompt would be "E5 LES Miniature Bulb, 5mm 14V 0.7W".

I placed an order for a seemingly suitable LED alternative in warm white, and was sent a 10-pack of miniature train bulbs - with 11 pieces in it.

Opening the switch is fiddly but nothing too complicated. I found that slices of thin rigid card helped keeping the knubs out of their holes. Truth be told what you want to do is only remove the front cap instead of the complete rocker mechanism. It took me seconds with slip joint pliers and a piece of rag.

Following an other forum post, it was advised to use some length of plastic tubing to access the bulb. I ended useing small nose pliers to screw the (plastic) LED replacement bulb in place. - A piece of heat shrink worked a treat when fitting the incandescent bulb later on.

Original bulb markings say : 14V 50 mA, confirming that 0.7 Watts is what we need. "E5 E5.5" is appropriate in terms of size.

The best reference for the job would be N9951903, with an average bulb life of 1000 hours  -  I'm close to 600 hours I reckon, all the others should follow this year.

Not fully happy with the result (see below), the LEDs were sent back to Amazon free of charge, and 14V 50mA incandescent bulbs were sourced from an eBay seller in Germany.

Look for '5 x Glühlampe E5,5 klar 14V 50mA 0,7W E5 Glühlampen Glühbirne'  if you need some. Total cost was 19.98€ for 10 pieces. Three arrived dead on arrival, one was a 2 Watts unit...

I'm convinced that retaining hot filaments is also a way to play safe by preventing condensation as much as possible.

Some issues :

• I lost track of the switch orientation and had to use a 12V power supply to identify the top part of the switch. You'd better label it before opening it.
• The LED was far too bright, and I had to add a 27 kΩ resistor to tame it. It's now a bit too dim, maybe 22 kΩ would be better. The resistor is soldered to a pair of spade terminals, inserted on the ground side of the bulb supply on the switch.
• The color was not quite the same, with LEDs I'd better have replaced all the 7 bulbs and save about 5 Watts.
• While having more than then specified power could overheat the switches, wouldn't it be good for humidity concerns to keep incandescent bulbs rather than cold LEDs ?