ditto!
 

Ditto Sal! Great work! I agree with you that the Xenon's look like what we had discussed trying to accomplish. I am going to order some tonight or tomorrow. Any fitment issues you can see with any of the other gages stock holes?

Thanks again Sal!

Cheers, Shane

Pics and details on howto prepare the Xenon 5W bulbs and mount them to the 3/8" copper pipe soon!

Re: ditto!
 

Shane,

Go ahead and order the Xenon 5W bulbs, They fit with pletty of room, much better fit than the 194 bulbs. I see no fitment issues. BTW - I ordered 10 bulbs, figured a few spares are a good idea.

Ron (MYSTERYTRAIN),
As you see I think the 5W Xenon bulb is the way to go for improving our gauge lighting. Now we need to work on the wiring as keeping the stock dimmer configuration may be an overload condition for the dimmer, but I'm not sure? Can we get specs for the headlight switch? would be great to know what the stock dimmer can handle.

I know we talked about and concidered using a relay to power the gauge lights and I think this is a good idea but I have yet another concern: after looking at the gauge wiring I see that the ground side for the gauge bulbs is done via the gauge case which is then grounded via a group of brown ground wires. So, we looked at the power side in detail but I fear we need to also look at the ground wiring and how this wiring is configured to be sure the ground can handle the extra current.

Ron, your thoughts please.

hollywood sells a right fit bulb, here in europe i am using led right to fit bulbs also, 23 euros a pop though! VDO made

I haven't been very successful in my quest for a small self contained dimmer module. I've been looking at marine stuff but nothing has jumped out at me. The 5 watt bulbs look nice but I image the current draw is now past the point where we can continue to use the factory harness. I think I mentioned this a few pages back but when I jump into this mod I think the only lights that I will leave on the dimmer will be the ones in the gauges..so what is that 8 bulbs? looks like they each are pulling .4 amps at 12 volts..yikes..so 3.2 amps not too bad. The harness in theory can handle 11amps .5mm = 20 AWG. The factory schematic shows the brown ground wires as .5mm and they are daisy chained from one gauge to the next. I don't know what the physical harness looks like but again..with just the 8 bulbs things aren't out of hand. The missing piece of info is the current rating for the dimmer. Ok, who as a dimmer to sacrifice for the good mankind? We can keep loading one up until it smokes.

subscribing!

Just a note of what may be obvious, but lets ensure the sacrificial dimmer is an orginal (read as OLD) one.

Does anyone have a simplified schematic (wiring diagram) of the 911 lighting system? I have the full blown wiring diagram but would like a simplified version for my document.

Thanks.

Geez, a dimmer for a 74-89 911 is $160! I googled 'porsche healight switch manufacturer' and came up with a brand called OEQ. Does anyone know who this is? I figured I would call try to get the specs for the dimmer. Does anyone know the OEM supplier?

Ron, not sure if OEQ is a supplier or a term? it also stands for Original Equipment Quality.

Sal,

Im subscribing now. thanks for posting all this.

I have one question. the 911 headlight switch appears to be very similar to some American made push-pull w/ rotary dimmer switches. Would a Mustang switch do the trick or one from an older truck? Should be fairly inexpensive at the junk yard. Just trying to think outside the box...

Thanks again for doing all the leg work here.

Kemo,
I'm not sure if we could use a Mustang switch but I would most likely think it's diffrent internally. The Stock 911 switch internally really is 5 switches plus one variable potentiometer output. (This is why the switch is so expensive!)

It has 2 12volt feeds coming into it:

<H3>FEED1:</H3> terminal 30 is the 12V input that feeds 4 of the switches plus the Potentiometer output the 4 switch outputs are L, R, K & 57 the pot outpot is 58a. This feed is used for all lighting except for the headlights. This is also the feed that we are adding the extra load to by using the 5W bulbs in the gauges. We are adding about 3.5amps extra to this feed.

<H3>FEED2:</H3> Then terminal 75 is the other 12V input that feeds a switch that provides output via terminal 56 for the headlights (basically they have one dedicated switch for the headlights that runs from it's own dedicate input 75).

So even though the Mustang switch seems simular in function I doubt it is as complex as the 911 switch. I really don't wish to replace the 911 one. We just want to know how much current the potentiometer can handle.

I plan to put a current clamp on terminal 30 (this is the feed for all the lighting except the headlights) to see what the curent draw is in the stock configuration. One other interesting design point is that the engineers also draw power from this same terminal when you pull back on your blinker stick to flash the hi-beams. I think they did this because if the headlights are on in low-beam mode and you decide to flash the hi-beams both elements are lit in the headlight bulbs. Most likely they where concerned that powering both elements from feed 75 would cause an overload problem. By the way this tells me that terminal 30 has tons of headroom to spare as far as current capabilities, if it did not the engineers would not have powered the hi-beam flash via this terminal. So the added load of 3.5A for the Xenon bulbs does not have me very worried as far as the rest of the switch goes, I'm only worried about the potentiometer within the switch. Another idea (From Ron) is to just move all the dimable gauge lighting from terminal 58a (pot outpot) to terminal 57 wich is a fixed 12v output and live with gauges that can't be dimmed. After looking at this wiring I really don't think we need a relay for the new Xenon 5W Gauge bulbs. the only danger is if you decide to drive around holding your hi-beam flash stick on! At worse this may blow your fuse for terminal 30 and you will lose all lighting but still have your headlights.

Lots to digest in this post but I'm looking at all these issues. Once I place a current clamp on terminal 30 and see what the draw is I'll have a better idea of where we stand. I will test the current draw with the hi-beams in flash mode as well. BTW - my car has H4 lighting so the draw will be slightly higher than the older cars while in flash mode.

do any of you guys need a headlight switch??? I think mine is starting to go, it still works but is starting to sometimes go on and off, when it goes off only the right headlight goes out, I just wiggle the switch and rotate it some and the light comes back on. It might be fine for a couple of night outing and then bam it does it again. Soooo, I guess its time to buy a new one.

I would be happy to donate the switch for further research into this project.

Awesome gatotom. Sal, here's your guineapig...

Gato Tom,
Once you take this switch out please contact me at sal.carceller@cox.net with your number so I get with you about shipping details. I will surely toast your old switch as I plan to see just how much current it will take to get the dimmer potentiometer hot or burned out. That part of the switch is seprate from the headlight side of the switch.

Thanks for offering up the old switch.

OK, now we need to come up with a valid plan for testing the switch. I was kind of joking when I suggested 'loading it up until it smokes' ..I think releasing the smoke is good for picking a Pope but we might need something more scientific for choosing a dimmer. I really don't like dash fires!

Ron, I think I should figure out what the current is going through the potentiometer in the stock configuration then add the extra load of the 5W bulbs. Next, bench test the switch with 15V and a load equal to the calculated load, let everything run like this for 24hrs but of course keep an eye on the heat being generated at the switch from time to time. What do you think? How long should we test for? Also if all is good after 24hr period maybe bump the load up 25%?

Sal, that sounds like a good plan. This is a hoot!

I have a donor headlight switch coming soon for load testing. Does anyone have hi wattage resistors say 1,2,3 or 4 ohm 50-100Watt resistors? The large resistors with the metal cooling cases? I will need some of these for loading the switch.

4 ohms at 12Volts is 3amps
3 ohms at 12Volts is 4amps
2 ohms at 12Volts is 6amps

You get the idea.

Thanks.