Keith - I wouldn't recommend the dual battery stress test idea... I think testing them like this - while it may weed out some prone to failure it may just create latent damage in others leading to later failure that may otherwise not have happened. If you are to stress test with elevated voltage it should not be so extreme 18V may be a more acceptable level its more like what a manufacturer might do for "burn-in" testing (24-26V probably not).

LED's in general are very reliable and have a long life expectancy.

However super-bright LED's are a little different. There were some technology advances that allowed higher output. However you can also get higher output from just running LED's at a higher current. Doing this is just a trade off of more light output for less lifetime. In practice the cheap ones from China you buy on ebay may be a combination of the 2 things...

How do you know what you have really got .... you don't...

There are 2 options - pay more to buy from a reputable vendor - who probably used better sources and at least may offer replacements (though for many applications replacement is huge PITA). Or you can add an additional series resistance (there is one built in to bulb replacement LEDs which sets the current level at a given voltage). If you add aditional resistance outside the bulb you can limit the current & brightness a little to move yourself along that tradeoff towards more reliability. Porsche does this even with the incandescent bulbs in the hard to reach locations - on incandescents less voltage dramatially increases lifetimes.

The existing Rheostat is such a series resistance - but it goes to all the bulbs and it is sized for the current load of incandescent bulbs which is way too little resistance.

You may find you need different resistances to each bulb type to get appropriate adjustments so fitting a new higher value rheostat may not be the answer.

Alan

Alan, I don't recall what you are referring too and I haven't gone back over everything. I am sure what ever I said, I meant was that 18v should be applied just to the bulb in short term wth 2 9v batteries. I have had no adverse affects from this, but if you had "quoted" me, I might be able to address this better. Sorry for any mis information.

Jim...you will remove the fan knob and drill a hole at an angle in the back side so that the fiber optic line points right at the fan picture on the knob. Just drill in a location of the knob so that it will not impact its rotary function. Drill as close up tto the top of the knob as possible...sorry, I don't have a pic of what I did.

The switches have been discussed in different threads in the past, but I personally see no need for it. There are some glow in the dark stickers that someone had made but basically, drilling out the switch faces and installing something else, then uplighting seems to me to not be worth the time. I have heard several say that they hate where the switches are. I love them as I never have to look at them and can just lay my hand over them and know exactly which switch I am on without taking my eyes off the road. To each his own. If you come up with something, post it, I am sure there are others that would follow your lead.

OK I'll quote you - maybe its not what you meant... but its what you said... and others may follow this advice...

Admittedly (and as noted by someone after) the math is a bit flawwed - but some people don't pay attention and may follow the idea...

2 x 9v batteries in series is OK due to both the lower voltage and those batteries much much higher internal resistance.

Alan

Yea...my bad and I missed the correction. Yes, 2- 9v batteries. I had 12v auto source on the mind I guess.

Just noticed one of my #74 LED (dash pod side lights) had 18V stamped on it.
Tested one white wide beam LED in the headlight switch and boy is that thing bright.

Going to switch out the rest of the pod switch lights now that I've found out about the 2 screwdriver/needle nose trick to free the switches from the pod.
(Can't get the small slippery old bulbs out of the switch with them buried in the pod)

Haven't tried it, but I think crazy glue on the end of a plastic toothpick might work.

Ernie - Slip some clear plastic tube over the bulb end - you may have to experiment with size - I had some to hand that worked fine - this was a tip from someone else that I tried and it worked very very well. I think it helped to stretch the end open wih some needle nosed pliers then slip it over the bulb and wait while it contracts back...

Alan

Thanks Alan and Keith.

Ain't fun trying to manhandle glass bulbs.
I'll see if I can rustle up some small rubber tubing.
Might even try some glue in the tube as lube and let the sucker bond to the dead bulb.

It's like the Zuffenhausen crew had too much model railroad experience and decided to doll up the switches with some of those wheat of grain bulbs.

Glad those #74 LED bulbs are manly and easy to manipulate. The wide beam bulbs also are flat topped for easier handling.

Keith,
I have been working on a somewhat similar upgrade. I have a couple of questions about the the pod switch led installation.
1) How did you file down the bases for the bulbs to fit? A small rat tail file or something?
2) Following Wojtek's schematics, do simply cut the particular wire and solder in a resistor in the line? Would any old radio shack resistor do the trick?
Still lovin' your car,

Sorry, been out of touch for a bit.

Any Radio Shack or electronics store for the resistors and just solder them inline. Cover with heat shrink tube.

For the filing, you can use a rat tail file, but that takes a while, I got smart and used a Dremel with a little barrel sander. You basically have to make a better wedge shape at the bottom of the LED. Don't try to modify the socket, I tried and F'd one up and had to replace it. There is enough plastic at the base to remove material before you get into the bulb. Trial and error.Take your time and you'll see it will work.

Good luck.


BTW, I never really posted any pics, but I did this same conversion to an 85. Dash and all. The instrument gauges were front lit of course, but the conversion worked out great. BTW, I just wired past the dimmer wheel....that thing is useless and there is no need to dim these.

Keith, Thanks a million. I am really glad I asked, I would have totally tried to file the socket and not the bulb. I too have just deleted the dimmer, I am using LED's to front light the needles and a speedhut reverse glo el gauge faces on my 82. Looks pretty nice (not nearly as nice as your car), the LED pod switches will be the finishing touch.

Here's a pic of the 85, though it was still light out. You don't get the full effect, but you can see how vivid the lighting is even when it is dusk. Note the fan switch is lit aas well ;) Good luck Bob!
http://img360.imageshack.us/img360/4896/8515mw4.jpg

So - what's the process involved in switching a frontlit cluster to a backlit cluster? Are they a plug-n-play swap (obviously losing the trip computer/odometer, I guess)? If not, how hard would it be and what would be the steps?

No Need.
Once you upgrade, the LED's on the frontlit setup look great!

That pic sucked,
Hopefully this is a little better