LED dashboard lighting upgrades

[Mike Stevens]

I have not done the Ignition yet as the bulb is a earth path on start up, which the LED cannot achieve. Hence a resistor is required in Parallel with the Led to allow the Alternator to be energised.

Assuming the original indicator bulbs were 2.2W, then the current through it to 'start' the alternator is about 180mA. 20mA for an LED replacement sounds about right, so a resistor of 68 or 82 ohms should serve to provide the extra current. (The calculated value is 75 ohms, but that's not in the E12 range!).

If you want to try, I can easily supply you with some resistors!

Cheers,
Mike.

[StagJonno]

Assuming the original indicator bulbs were 2.2W, then the current through it to 'start' the alternator is about 180mA. 20mA for an LED replacement sounds about right, so a resistor of 68 or 82 ohms should serve to provide the extra current. (The calculated value is 75 ohms, but that's not in the E12 range!).

If you want to try, I can easily supply you with some resistors!

Cheers,
Mike.

Stag cluster bulbs are 1.5W which changes the numbers a bit (100ohms), though Gil @ 4Sight supplies a 220ohm resistor for this purpose, and has many happy Stag and TR customers.

[Mike Stevens]

Stag cluster bulbs are 1.5W which changes the numbers a bit (100ohms), though Gil @ 4Sight supplies a 220ohm resistor for this purpose, and has many happy Stag and TR customers.

Thanks for the correction! 2.2W did sound like a bit too much heat in there.

I'm not surprised that a lower current is enough to 'start' the alternator. I wouldn't have expected that the current through a 1.5W bulb would be only just enough!

Cheers,
Mike.

[marshman]

Assuming the original indicator bulbs were 2.2W, then the current through it to 'start' the alternator is about 180mA. 20mA for an LED replacement sounds about right, so a resistor of 68 or 82 ohms should serve to provide the extra current. (The calculated value is 75 ohms, but that's not in the E12 range!).

If you want to try, I can easily supply you with some resistors!

Cheers,
Mike.

Probably teaching you parents mother to suck eggs but please make sure you use a resistor that can cope with the power. In this case 2W or so. Normal small resistors are only rated at 1/4 or even 1/8th Watt and if used in this application could glow red hot and if touching other wiring melt through the insulation etc....

So a) get the right value resistance, b) make sure the power rating is high enough - (current x current x resistance = power) c) take care when mounting the resistor, it will get warm.

To be honest I know LEDs are good, I have them almost exclusively lighting my house, but I don't see the need to replace every lamp on the car with them. Often the old filament lamps are dim because the glass has blackened and contacts are corroded. In the case of the igniton indicator you are replacing one lamp with two components, LED and resistor, so very simplistically more to go wrong and harder to track the fault when it does. Those that know me also know I have similar view on electronic ignition. It's all part of "the charm"of on old car! This of course is my opinion and nothing against anyone who wants to "improve" their own car, just take care and watch out for unitended consequences .... e.g hot resistors as described above.

Roger

[Mike Stevens]

Probably teaching you parents mother to suck eggs but please make sure you use a resistor that can cope with the power. In this case 2W or so. Normal small resistors are only rated at 1/4 or even 1/8th Watt and if used in this application could glow red hot and if touching other wiring melt through the insulation etc....

So a) get the right value resistance, b) make sure the power rating is high enough - (current x current x resistance = power) c) take care when mounting the resistor, it will get warm.

To be honest I know LEDs are good, I have them almost exclusively lighting my house, but I don't see the need to replace every lamp on the car with them. Often the old filament lamps are dim because the glass has blackened and contacts are corroded. In the case of the igniton indicator you are replacing one lamp with two components, LED and resistor, so very simplistically more to go wrong and harder to track the fault when it does. Those that know me also know I have similar view on electronic ignition. It's all part of "the charm"of on old car! This of course is my opinion and nothing against anyone who wants to "improve" their own car, just take care and watch out for unitended consequences .... e.g hot resistors as described above

Thanks Roger, a worthwhile addition to this thread. I was aware of the power dissipation. Being an electronic engineer with some 45 years experience does have some uses!

Cheers,
Mike.

[StagJonno]

Top tip for those fitting the warning cluster LEDs from 4Sight Automotive. As both Mike and I found out, the LED tops do not withstand much twisting force and it's too easy for them to become detached from the body. As the bulbholders have to be opened up a bit to accommodate the slightly fatter bodies, you end up doing several trial fits on each holder and as the hole may not allow free reunning of the bulb, excess strain is put on the LED-body fixing. The LED body of a knackered bulb will accept an M5 screw. Add a drop of Nutlock and you've got a robust tool to confirm fit/ clean the thread2016-02-18 18.49.45-1.jpg

Jonno