Monday 31 May 2021

BMW E30: Digital Clock quick LED upgrade

The bulb had blown in my E30’s digital clock, so I decided to repair it with a quick and easy LED upgrade. It’s another bulb load of power taken off my 35 year old dash wiring so can’t hurt. 

The bulb-holder is integral to the working of the lamp, with the metal clips that hold it in place also acting as live/earth contacts. LEDs built into such a holder can be purchased specifically for replacing bulbs like this if you want to go that route, but if you have a bunch of cheap LEDs lying round and don’t want to spend any money then read on.

Simply remove the plastic holder and cut the old bulb away from the two pieces of metal. Solder a cheap yellow or red LED onto the metal contacts in the place where the bulb was attached and bend the LED stalks back on themselves so the diode is pointing the right way, as in pic. A pure-white LED would probably be better, but they use more wattage, will probably require a spend and cheaper dome LEDs work fine anyway.

The bulb for the clock has a resistor built in anyway, so the LED will run fine and not pop without modification, but if you find it is too dim or bright to you can ‘piggy-back’ another resistor across the stock one to raise or lower resistance to suit. A calculator to help work out what resistance you need are easily available online, but trial and error is best if you have a bunch of LEDs / resistors lying round.

You may want to cover the recess at the back of the clock with electrical tape to stop light spilling out.

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