W123 - Cluster LED upgrade, seat belt light stays on.

[Timelord]

I am working out the w123 300td cluster led upgrade. Current issue I've run into (and not had chance to mess with fully) is the seatbelt warning light only goes dim rather than going off as it does with an incandescent bulb. Is this another bulb such as the alternator bulb (which I have worked up proper solution for, to be tested and written up in the next week or two) that does magical things other than simply indicate?

[ngarover]

Originally Posted by Timelord

I am working out the w123 300td cluster led upgrade. Current issue I've run into (and not had chance to mess with fully) is the seatbelt warning light only goes dim rather than going off as it does with an incandescent bulb. Is this another bulb such as the alternator bulb (which I have worked up proper solution for, to be tested and written up in the next week or two) that does magical things other than simply indicate?

No answer, but I would love to see pictures of the upgrade and the steps you took to do it when your done.

[Yak]

Originally Posted by Timelord

I am working out the w123 300td cluster led upgrade. Current issue I've run into (and not had chance to mess with fully) is the seatbelt warning light only goes dim rather than going off as it does with an incandescent bulb. Is this another bulb such as the alternator bulb (which I have worked up proper solution for, to be tested and written up in the next week or two) that does magical things other than simply indicate?

I think the bulb is supposed to be single purpose, no magic involved. However it does link up to the warning control module that may/may not behave itself anymore. Or the buckle may be worn over time, so it may not be fully opening the switch to turn off the bulb.

[Timelord]

Got a chance to do some quick tests. Seems that it sends a small current through the bulb to keep the time delay circuit from retripping.

Figuring a 120ohm (roughly 1.2 watt bulb resistance, while lit), 5+ watt resistor mounted on a heatsink should do it, though the led bulb I selected seems to be particularly good with lighting at very low voltages and may require a zener diode or some such.

The easy solution would be to disable the light or leave in an incandescent bulb, but I am fairly dead set on installing LEDs.