Instrument LED bulbs

[clunker]

I am changing the bulbs in the instrument cluster, as I have them it for other reasons. There was fairly clear post as to what LED bulbs/color should work posted by 66andBlue in 2013 (reposted here), and now superbrightleds offers BA9s base LED bulbs in various colors, including warm white.

The general warning is that the alternator warning light cannot be swapped for an LED as it specifically requires a 2W (incandescent) bulb for that circuit to work, presumably because the resistance draw of the 2W bulb is needed. I assume that bulbs resistance is  (12v * 12v / 2W =) 72ohms.

In the spirit of no dumb questions -

Given the 1-LED red bulb BA9S-R-90-12VAC from superbrightleds is rated 0.02A at 12v (so 0.24W), we can assume the resistance is (12v / 0.02A =) 600ohms. To get a 72ohm circuit (as per the 2W incandescent) and 2W power draw, I propose adding an 82ohm resistor in parallel with the LED (using 1/72 = 1/600 + 1/82) and the circuit will work as expected. Quite likely I missing something, and of course it assumes it is possible to physically patch in that resistor, but has anyone tried this?

[mmizesko]

Charles,  Nope, I did not try tpo add a resistor.  Just followed the instructions above.  Very Happy after 6 years.

Mike Mizesko

[Jonny B]

This is from a good friend of mine, fellow Pagoda owner, and electrical engineer:

Totally agree with the idea. On a practical note:

1) Those green LED's will fry your eyes. If adding resistors, why not experiment with series resistance for the turn signals.
2) Test all this out before installing everything!

I can vouch for the green LEDs, they are like little green laser beams on the dash!

[clunker]

So I added the 82ohm resistor and that seemed to work fine with a 1-led red for charging indicator - charge on with ignition on/engine not started, charge light off with engine running. I also checked battery/ alternator charge voltages are just fine.

I did use 1-led's  on the turn signals - the 4-led's were too much!. I also used a 1-led (white) for the center unit illumination, again 4-led seemed too much but ymmv. I am using 4-led x2 on tach and speedo lights and they seem about right. I too had to keep the 2W incandescent bulb on the low fuel slot: the 1-led is just too wide to fit in hole - maybe someone can locate a slim version BA9s one day.

I used a 5W rated 82ohm resistor, but anything over 2W should be fine. I patched it into the cluster plug - soldered in patch wires inside the plug and ran them outside the plug unit and put resistor there, suitable heat shrink sealed.

I also ran patch wires out of the plug for the rheostat short - I refurbished the rheostat but the resistance spring too far gone, and not sure if the LEDs dimmable anyway (did not check).

I attach an amended version of 66andBlue's original diagram reflecting what I have used.

[66andBlue]

Nicely done - thank you!

[TEJOLX47]

Dear Charles,

Thank you for the very informative posts on the subject.
I have to remove some of my instruments to repair, so I thought I could upgrade normal bulbs to LED.
I have two questions though:
1. Should the lamps be alternate current or direct current; you mention a Bulb BA9S-R-90-12VAC which is for alternate current and I thought (maybe I am wrong) the dashboard uses direct current.
2. Do the LED's produce to much heat when operating for a while; should we be concerned with that?
Many thanks.
Francisco

[JamesL]

DC 12v. Power is off the battery or alternator.

One of the benefits of LED in terms of efficiency is that a much greater portion of the power draw is used to generate light, whereas with older bulbs, most of the energy can end up being used to generate heat (think of what a bulb filament is). For the same “lumens”, less power is needed as less energy is used to create (wasted) heat.
So the answer is that heat is less of an issue with LED than old bulbs

[clunker]

Exactly as James said - 90% of incandescent bulb energy goes as heat/10% light, LED 10% heat/90% light, so for same light (lumens) only 11% of power needed and only 1.1% of heat generated (very very broadly speaking of course!). And pretty much all LEDS are DC, those in AC circuits have rectifiers to convert.

[TEJOLX47]

Thank you all!
I am on my way to "futurize" my Classic.
Cheers

[getsmart]

Hi all,

Does anyone know if the remaining regular 2w bulb can be replaced with an led (see my question in red in the pic)? I'm not sure if I remember correctly but I might have read that it can be but the problem that most leds don't fit, is that correct?

Rgds, Joe

PS . I just re-read and did see Clunker make a reference to it in reply 3 above - I think I can apply a little dremel grinding , only need a mil off or so for the leds I got

[getsmart]

ok I can now see one reason the low fuel light can't be updated to led - the housing cannot be easily ground as it is a tube that goes all the way to the front of the gauge to limit light pollution into the rest of the gauge. Looks like it will stay as an incandescent globe for now 

Hi all,

Does anyone know if the remaining regular 2w bulb can be replaced with an led (see my question in red in the pic)? I'm not sure if I remember correctly but I might have read that it can be but the problem that most leds don't fit, is that correct?

Rgds, Joe

PS . I just re-read and did see Clunker make a reference to it in reply 3 above - I think I can apply a little dremel grinding , only need a mil off or so for the leds I got

[teahead]

green turn signal LEDs...do they flash quickly?  DId you have to add resistors?

[BobH]

I think you would only need to add resistors to "dim" the brightness, if the dash indicators are flashing more rapidly than normal, it could be one of the external indicator/flasher bulbs have failed, either front or rear, have you checked?

[getsmart]

green turn signal LEDs...do they flash quickly?  DId you have to add resistors?

If replacing blinker incandescent globes with leds then the blinker relay needs to be replaced with a low current electronic relay. There are many brands available and quite a few threads on this forum. I used a cheap cf15 12v led flasher and adapted the pins to suit the Mercedes plug.

Rgds, Joe

[ejboyd5]

I cannot embrace the current craze to "upgrade" instrument lamps to LED since it is my practice to keep cockpit lighting as dim as possible so as not to distract from my outside vision. LEDs' proper application is to enhance the visibility of your vehicle to others and to increase your forward looking illumination.

[getsmart]

There is a very excellent reason to embrace leds and that is the lowering of current in already aging cabling 

[teahead]

hey, I've already replaced all the LED bulbs in the cluster...EXCEPT the 2a bulb.

I can't recall, but does that light come on when you have the ignition on?  Or does it ONLY come on w/low fuel?

I put a new BA9 2a bulb in there...nada.  I put the old one in there...nada.   I tested both bulbs...all OK.

Anyone know?

[rwmastel]

...EXCEPT the 2a bulb.

I put a new BA9 2a bulb in there...

2a bulb??

[WRe]

Hi,
the bulb you marked is the fuel reserve light.
It could be replaced by a LED but the opening for "low fuel level" warning light in the housing is too narrow to accept a 1-LED.
More info see here: https://www.sl113.org/forums/index.php?topic=19084.0
...WRe

[teahead]

I meant 2w, not 2a.

Okay, so I guess obviously if the tank is full, one would never see that light bulb come on w/the ign on.

So..I guess to play it safe, I'll keep the incandescent bulb there (pretty sure I can fit a 1-LED in there) and of course, the IGN idiot light.