Tachometer illumination bulb removal

[georgesgiralt]

Another way to do this is to tag the plug and the printed circuit board once the plug is set correctly. then, when you want to do a testing without the cover, all you have to do is to align the tag to get the proper wiring/plug position.
(I use one of  the cover screw to align the tag on the plug with the cover on, then i tag a line on the printed circuit board from that screw hole to the plug pins. Choose a permanent marker pen of a contrasting color or nail paint )

[dogshome]

I just pulled my tacho since I was smartening up the PO indicator beepers. The white plug came out fine and I noticed a location 'half moon' on the tacho side. That's strange/ what goes into that?

Answer a bit of half moon shaped white plastic that's long gone. Note to self - check when plugging back in and mark it!

The bulbs are welded into the sockets using a 200mA current for 10 years....

Also noted, these are T10 not T5 as found on the R80 etc if you are switching to LEDs.

Also noted LEDs 40mA, generator 200mA to start. I don't like relatively large wattage resistors (or undersized 330 or 470R ones) so (as an electronics engineer) am leaving the bulb there. The hi beam one is in best shape...

[dogshome]

Conventional bulbs have one wire on the left flat side and it's mirror on the other side. One connection per flat side.

Conventional bulb holders have two tulip contacts that work fine.

BMW R65 dash lamp holders (and probably the odd BL, Fiat and other antique cars dash lamps) have a double tulip that relies on one wire, one connection per flat (can you see where this is going yet?).

So plug LED into BMW bulb holder and you have a short circuit.

The solution is simple, drill the tiny through board plated holes on one flat and voila, connects like ordinary bulb. Both sides, I only went part through to maintain contact area. Hopefully this will save some frustration  8-)

Piccy coming....