odonnell

You mean V=IR? Energy is a unit of charge times voltage (Joule = Coulomb x Volt)

use2windsurf

Correct, I used the flexible LED strips with built in resistors. i think most white leds have about 3V forward voltage so I would put a 560 ohm resistor in series with each LED, connect them in parallel and drive them all with the $3 PWM dimmer I posted earlier. My profile pic is my cluster driven like this.

1987 Red 944 N/A *** NOTE- I probably posted from my iPad, please excuse any typos, bad punctuation or odd grammar, if it is unreadable, it probably was posted from my iPhone.

use2windsurf

here is how i did mine. first pict shows the LED strip , you cant see it when looking at it from a normal angle. 2nd pic shows it at full brightness.
I used these LEDs:






1987 Red 944 N/A *** NOTE- I probably posted from my iPad, please excuse any typos, bad punctuation or odd grammar, if it is unreadable, it probably was posted from my iPhone.

odonnell

I was going to shoot for about a 2W draw on each bulb (using resistors in series with each LED) and use the current in each branch to calculate that value (2W = current squared times resistance). I just need to hunt down a wiring diagram for the early dash so I can do this correctly and not jank-ify my wiring any more than it already is.

H.F.B.

May be this old thread could help complementary:
https://rennlist.com/forums/924-931-...arly-cars.html

and this about the color

https://rennlist.com/forums/8920708-post35.html

use2windsurf

2 watts is too much LEDs will fry, the leds are probably rated at 20milliamps at 3V or about 60 milliwatts. the 550-650 ohm resistor in series will give you that. I think the incandescent bulbs originally in there were rated at 2 watts.



As someone else said though, this may still not be bright enough if the light tubes on the cluster are not up to snuff. hope this helps.

1987 Red 944 N/A *** NOTE- I probably posted from my iPad, please excuse any typos, bad punctuation or odd grammar, if it is unreadable, it probably was posted from my iPhone.

86 951 Driver

I used the drop in replacements from superbrightleds.com they worked great. I also fixed the reflective material with aluminum foil. I used cool blue for the color. It looked great.

Lorenzo78

Anyone tried this kit?

http://r.ebay.com/O0lIxU

It seems specific for our cars, I'm very tempted to give it a try

use2windsurf

E=IR is also a common way to show Ohm's Law, that the way it was taught in the first EE circuits class I had in college.

FIA-F1

Alright, I'm really frustrated now. I have taken out my instrument cluster trying to get my dash visible at night again. Here's my path...
Replaced stock 944 incandescent bulbs with LED kit made for the 944 (has 3 sets of 4 LEDs to replace the triangular clear plastic lens attached to the bottom of the instrument cluster).
One of the 3 LED strips had a noticeable light shift randomly going a bit dark. It turned out two be one LED bulb going out periodically.
I replaced the LED with stock 4watt incandescent bulb...it was so dark, could not even read the gauges at night.
I bought the SuperBright LED bulbs but was not any brighter than the 4 watt incandescent. (I mean useless dark).
I reinstalled the LED strips. Center set is now bright and visible. Outer sets are on (bulbs burning) but useless dark.
I'm tired of pulling my instrument cluster out. I get the impression my instrument lights are not getting enough power. Any suggestions?

Raceboy

I made a LED conversion on my turbocharged 924 few years ago. Stock bulbs just barely light the gauges and are as yellow as it gets and it is totally worth it. Dimming works but is is marginal. Driving in dark is pleasure now, not too bright but everything is clearly visible. I just soldered a LED and resistor to stock bulb chassis, so it is kind of bolt-on now.

FIA-F1

So maybe I need to solder a resistor to my LED light sets. What ohm resistor did you use?

catamount

Have you checked the condition of the grounds in your car? Bad grounds can cause all kinds of wacky issues. I do believe the ground for the instrument cluster is located under the dash on the firewall. Give it a good cleaning then see what happens.

FIA-F1

that sounds like a worthwhile step regardless. thanks.

Ed Scherer

It sounds like some of you guys are retracing some of the same steps we 928 guys took a while back.

I did the instrument cluster LED upgrade (and actually don't have a single incandescent light left anywhere on my car other than the driving/fog light H3 halogens) on my '90 928S4 a couple of years ago. Fantastic results. The dimming issue bugged me enough that I spent quite a bit of time developing a specialized dimmer module that adapts your existing dimmer rheostat/potentiometer to control dimming via a microcontroller-based PWM circuit. You can read the whole adventure in the thread PWM dimmer for instrument backlighting after upgrading to LEDs. There's also the write-up Converting Porsche 928 Interior Lighting to LEDs, which certainly wasn't intended for 944s, but has some content (general LED lighting principles, etc.) that might be of value to you anyway. It would be nice if somebody in your group took the initiative to do a similar write-up for your cars (or at least a replacement bulb cross-reference) so you don't have to have numerous people doing a lot of trial-and-error to find the optimal set LED replacement bulbs.

To date, I'm pretty sure the dimmer module (AILD-1) has only been installed in (quite a few) 928s, but I certainly wouldn't mind seeing someone try it on 944s (and/or other older Porsches that also use similar rheostat-based instrumentation lighting).