Lotus Elan

Instrument lights

PostPost by: 69S4 » Tue Sep 11, 2018 7:56 am

The Veg wrote: The question is whether the lamp should be so dim, because I have no prior experience with these. I think the answer is 'no' at this point, so I'm looking at some LEDs so I won't have to go in after them again for a while.


It's hard to tell just how bright a bulb is from a photo but the bulbs in my instruments were so dim I couldn't see the display at night. Like you I checked the voltage to the bulbs and the earths but couldn't find anything to blame and the bulbs in the other instruments were fine. Rather than just replace them I changed to LEDs about a year ago and it has made a substantial difference. From memory the LEDs were around 100 lumens and that's about as bright as you'd want to go. Any brighter and light spill round the edges would become distracting.

Both bulbs were ordered as warm white (3k) but annoyingly the one in the tachometer seems to be colder and at night you can see the difference. It's no big deal and I'll get round to changing it eventually but it's something to check for when buying them.
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PostPost by: billwill » Tue Sep 11, 2018 12:24 pm

For want of a nail a shoe was lost.....

Did you check the voltage across the bulb itself?

Are the other bulbs in the dash doing the same?

Extract one of the other bulbs and test that too.


Note the dimness of old bulbs is usually due to metal evaporation from the filament and coating the inside of the glass with a thin layer of metal. Such bulbs are noticeably "dark glass", If your glass is clear and it is still dim when connected directly to a 12v battery, it must have been designed for a higher voltage.

The markings can usually be read with a good magnifying glass such as a jeweller's loupe.
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PostPost by: billwill » Tue Sep 11, 2018 12:28 pm

A fresh thought strikes me, we have been assuming that you are referring to one of the panel bulbs used to illuminate the instruments at night! If that is actually the ignition warning light of an alternator a whole fresh set of rules apply.
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PostPost by: The Veg » Tue Sep 11, 2018 9:04 pm

Good point Bill, but no, it's the instrument illumination. Reminds me too of the older BMW motorbikes in which if you lose the charging light, you lose the charging system.

Thanks Stuart for the practical advice on selecting LEDs. I'll bear it in mind when I order.
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