Jadz928

This is all excellent info.
Adam,
I'm assuming you are using white LED? Did I read you correctly that you used a std bulb in the head, and wired LEDs to the fan switch and sliders (2) in series (to the std bulb)?

Steve,
I wish I understood what you wrote. Okay, if I have 3 LEDs hard-wired in series (all w/built it resistors or not?), then in same series, 2 resistors, one fixed, one variable (50-100K trim-pot?).
What would the rating be for the fixed resistor?

I'm sure it would help to know what kind of LEDs I'll be using.
Adam,
What LEDs did you use? Where did you find them?

I just bought these Red LEDs from Autolumination
The #74 is a replacement option for the Osram 2721 instrument light.
I ordered 5 red LEDs to replace the bulbs in my pod switches. The have built-in resistors.
These are what I'm considering for the hvac head.

Chuck Schreiber

Adam,

Got any pics, or maybe you had Tony Harkin come over and do the photo shot??!!

I'd like to see how you set that up. Call me dumb but Where do you get fiber optic cable??Hobbie store, Radio shack, home depot?

Jim, Let me know how those bulbs work. I had the pod switch bulbs because they don't give off hardly any friggin light whatsover!!!!
I just received the Osram replacement bulb for the sliders and it looks to be the same one for the pod switches. (Osram 2721) If so I'm going to just put in the bulbs you were considering. BTW, you are going to use red LED's and the ones in the pod are white with colored areas on the switches themselves. Green for the lights, red for the def. etc.
Any reason why you went with red. Will white do the trick?

Man, this could change the face of 928 interior illumination as we know it!!!!!!!!

Chuck Schreiber

Jim,

Just pulled the trigger on the superwhite led's. I'll put them in the HVAC as well as the pod switches. Thanks for the info.

Jadz928

Okay, I've been researching LEDs...
I need help to determine what trim-pot (variable) resistor to use.

Here's what I got so far:
(1) 5mm red LED - 20Ma max, Vf 1.8/2.4 min/max
This will be used to illuminate the fan control switch
(2) 3mm red LED - 28Ma max, Vf 2.25/2.6 min max
These will be used to illuminate the the slider controls.

So based on this resistance calculator , I will need a 360K resistor to correctly wire these 3 LEDs in series.
I used 13.4V power supply instead of 12V.

So is it possible to add a second trim-pot resistor to allow the LEDs to function efficiently w/the stock dimmer?

Btw, I found tons of interesting LEDs online, but will start experimenting
w/Radio Shack. From all the info I could find, it is a reasonable choice.
Good LED info site
LEDs and where to get them
Another resistance calc
LED basics and tech data

Tony

Go find a house where they are installing fiber optic pool lighting and find the pool builders supplier.

Im sure any search on this here internet thing will find somehting?

Normy

This is a fascinating thread!

I have all sorts of problems with my AC control head. It only works in the up-arrow and defrost positions, and if you move the slider to one of the others…it will even turn off the AC compressor. I took the unit apart and noted some corrosion on the curved metal strips that form switches for the setting slider. I “cleaned” them with a pencil eraser, making them nice and shiny again…to no avail.

-Any ideas at this point, short of paying Mark Anderson for another control unit?

Well, while I had the controller apart, I decided to try to mount some red LED’s in place of the tiny clear bulb that Porsche installed at the factory. Like most people here, if you grab my slider ***** and pull…they pop out in your hand. Someone at some point took the controller apart and cut the fiber optic cables. I had resigned myself to never seeing them lit up again…until now. Cool idea, mounting LED’s! Well, the LED’s I installed in the unit [two, 5mm, 12 volts] do the job just barely. Yes, the control head now has red illumination for the metric temperatures and position settings, but they are very dim. More needed, I guess.

NOW…it seems fairly easy to solder in some LED’s into the sliders…but why do you need resistors? I can solder, but I really don’t have much knowledge of electronics beyond the basics. And I don’t use my dimmer anymore since I have the Speedhut gauge illumination, and I’d like more light at this point, not less!

Normy!
’85 S2 5 Speed

Chuck Schreiber

JIm,

The #74's from your previous post should be plug and play for the Osram 2721's right? I'm going to try this first and see what kind of illum. it produces. Hopefully good results. If not, back to the drawing board with Normy. Let me know how it goes.

Jadz928

Normy,
(2) 5mm LEDs... Do you have the specs on them? Where did you install them? Do you know if they had bult in resistors?
Two important specs to be aware of; MCD which is their brightness (it can range from 10 to 6000? or something like that... I'm still trying to find a scale for this number), and Nm which is their color range Link to LED color spectrum, check FAQs
Here are the reds:
NEAR-INFRARED
780nm very dim cherry red when viewed directly
770nm dull, deep cherry red when viewed directly
740nm deep cherry red

RED
700nm deep red
660nm pure red
645nm pure bright red
630nm 'HeNe laser' orangish-red
620nm distinctly orange-red

ORANGE
615nm reddish orange
610nm pure orange
605nm amber

- btw 645 and 660Nm would be ideal.
As far as resistors go... If you run a few (resistorless) LEDs in series, it is required to resist the circuit (12V) so that the LEDs can operate efficiently within their nominal voltage range (2-4V?). Otherwise they will melt and smell bad.
I'm going this route with the HVAC head because it will be cheaper, I can fufill my specific needs, and if all goes, well, be able to use my stock dimmer switch.

Chuck,
The #74 are plug-n-play, but I'm not to sure what MCD rating they have. I have a feeling they are on the higher end and may be too bright. We will see.

If any of this is incorrect, please correct me as I'm still learning. I need all the help I can get.

Thanks!

Chuck Schreiber

Thanks Jim.

Keep us updated with pics!!!

Normy

Jim-

I'm pretty sure that the LED's had some sort of resistor- there was a bulge in one of the wires. They had the red and black wires pre-soldered.

They came straight from the rack at radio shack, and they said 5 mm/ 12 volts. I don't have the packages any more, but I mounted two of them and the result is a bit dim. Not sure what frequency the light is, but it is a deep red.

I basically followed the wire from the existing bulb back into the unit and wired the LED wires to its mounts. It works....kinda!

N-

Chuck Schreiber

Jim,

Just got the #74 led's in tonight. Installed them in place of the Osram 2721's on the pod switches, Wow!!! What a difference!! They are plug and play. The old bulbs would hardly even shine through the switches, but these puppies were bright!!!

Ok, the light switch and fog switch look good, the defroster switch needs to be recolored because its faded and looks bright pink with the led behind it. Not too bright though. The rear wiper switch (pod mounted on 79 MY) and the trip reset were way too bright. I used a permanent marker and painted over the end of the led and it toned it down to where it looked good!

Overall, it made a huge difference on the switches, looks like a new car. But, now it kind of dates all the other illumination thats there. Pod ill. looks dull now but I'm thinking about doing the upgrade to led's there too.
Now for the HVAC unit!!

Definately a nice upgrade for any model year!!! Thanks for the research on the bulbs Jim!!!!

Jadz928

No problem Chuck... I'm glad it is working for you. I'm still waiting to receive my red LEDs, and hope they serve my purpose (read inexpensive upgrades). I ordered 5 but will save 1 for the HVAC. I will find something else for the defrost switch (if anything, a white halogen). Thanks for the tip.
I've sorted thru the HVAC head and am working out an idea. I have some LEDs on order, and will post further after I've experimented.
Taken apart so far...
Check out Speedhut to finish out your pod. I will be ordering soon, and if you choose to wait, I can give you my results (which I hope to be similar to Normy's, being what I'm looking for is similar). You can customize based on you personal needs. Cool! (no affiliation, naturally).
I haven't made a decision on my gage faces because I haven't determined whether I will change my speedo/odo over to kilos, or stay miles and install a 180 mph max gage. It will be in red whatever I chose as that is what I'm going for... something btw an Audi, KITT, and the Duke of Hazard (read red-neck)

Normy

Heh! Jim that's a kewl icon!

-Here's a few pix of the Speedhut reverse-red gauges. This one is with the garage light on...

N-

Normy

A moment later, garage lights off. The Kodak digital cam I have doesn't really do a good job of showing the gauges at night- they are nicely lit, no trouble reading them at all. I reinstalled the bulbs so the white painted needles appear.

N-

Chuck Schreiber

Jim,

Looks like you're deep into it. Let me know how it comes out. BTW, to ill. the fan switch, do you have to cut anything out? Didn't look like the fan was translucent on mine. Also, does one bulb light the whole face of the HVAC? (other than the sliders)

Normy, gauges look good. I'm sure they're better in real life as you say. Pics of lights are always hard to take. BTW, you said you left in your bulbs as well so you could see the needles?? So you have the stock bulbs and the reverse indiglo set up on the dimmer right??!!

I was thinking, can speedhut set up something in reverse indiglo for the clock? (early models have round clock with same font as gauges.) I thought I'd start there, new stereo will obviously have good illum. and then the HVAC. Gauges will be last, pod switches now look good with led's!