Replacing speedo light

maxum_101 · #1 09-01-2009, 08:30 PM

looking at the back of the speedo, i dont see anyway of changing the bulb.
as for the other guages.. its straight forwad on changing the bulbs out.

anyone know how to change the speedo bulb?

also looking at my fuel guage... it seems not as bright as the other guages, mind you i have just put in all new bulbs in the guages and the others are all nice and bright except for the fuel guage. is it just the way the guage is built (internals) or could it be something else?

Blas · #2 09-01-2009, 08:39 PM

I'm currently working on the dim lighting problem with Smith's instruments. I have some additional material coming in the next few weeks. LED's appear to be the wa to go. Light is not yellow. I had a call out for broken gauges on SCOF. I now have an AMP, oil temp and water temp gauges to experiment with but not speedo, tach or oil pressure gauges yet...Info as it comes available.

Got the Bug · #3 09-01-2009, 09:02 PM

Blas,

Steve (Panavia) has done some mods on the stock SPF dash lights so he may be able to provide some additional info on his findings.

Chilibit · #4 09-02-2009, 05:56 AM

On mine the bulb holder is merely interference fit into a hole, it does not even rotate to lock. Just pull it out. 2440

Blas · #5 09-02-2009, 11:51 AM

One thing I have found so far, it that the gauge lighting intensity varies a little depending on how far you push the bulb and its holder into the gauge socket in back. Now, if you are using a different sized bulb (length-wise) the possibility also exists that you can push the light assembly too far into the metal gauge housing and have the bulb actually resting up against the inner-workings of the gauge. I have confirmed this on the oil and temperature gauges so far. I have not checked the AMP meter for this problem yet or any of the other gauges. Having the bulb against the instrument internals will affect the gauge reading by limiting or preventing needle movement.
If you are using the standard bulb and holder, this should not a problem.
Here is a quick overview of my findings so far:
All of the light entering the gauge needs to reflect around inside the instrument housing to reach the 4 small light windows located on the gauge face. The gauge face itself is set back from the front glass about ~3/16”. The ring of material that supports the face has 4 light windows (opaque white areas) on it. This is where all the illumination enters the face of the gauge. The area of the light windows is maximized and cannot be improved on. The real problem is that the outside diameter of the gauge face (and the 3/16 ring of material that sets back and supports the gauge face) has only ~1/16” of clearance all-around with the ID of the instruments metal enclosure. (in other words: The ID of metal enclosure is ~1/8 larger than OD of instrument face – so you have ~1/16” clearance all around)
So all the light needs to be directed into this ~1/16” wide and ~3/16” deep slot after finding its way around the instrument internals which block any straight path of the bulbs light beam, except to the top light window.
So clearly the solution is more light. But larger wattage bulbs mean more heat. And the gauge face is some kind of plastic which distorts and melts with more heat.
I have made 2 LED prototype light sockets so far. One is a single LED and one with Double LED’s. The biggest improvement so far is that the light emitted by the LED is white not yellow. That alone makes the gauge easier to read. I had originally hoped to be able to make a bulb fixture to aim 2,3 or 4 small LED’s directly at the 4 light windows on the gauge face, but that’s appears impossible to do.
As some of you know, some LED are not 12v and require a resistor on the “+” side to cut the voltage down. Which leads to another problem regarding just how much voltage is in the wiring at the instruments. So far I’ve seen between 10.2 volts and 12.2 volts. On paper you should be able to get 14 volts to the bulbs. Make a big difference when sizing the resistor…
The dash light dimmer is another problem. Many different styles with one thing in common – all cheap.
FYI: Sometimes bypassing the dimmer all-together make a big difference in the gauge lighting…
So in closing:
I have some new 12V LED’s coming in the mail. This should eliminate the resistor problem. And since I have no speedo, tach or oil pressure or fuel gauge instruments to test yet, So I’m unaware of any unique internal lighting problems with these instruments. But I know the tach has a different lighting configuration that will require a different approach for sure. Thanks to those who have sent me the broken oil& water temp instrument and the AMP meter. I still need the others if anyone has broken units laying around.
I’ll post more results as they become available…

maxum_101 · #6 09-02-2009, 12:58 PM

thanks blas for the info

so the bulb in the speedo cannot be changed. its internali had 2.5 watt bulbs in the guages before and replaced them with 5 watt bulbs. big diffrence there, i bought some led peanut bulbs to test put ... has 2 small leds but they are red...haha so have to go back to exchangei have also seen 194 bulbs in led from some online light shop, the only guages that look weaker then the est are the speedo and the fuel guage.

gonna play with some more things that i want to try out and will report back with what i find

RedBarchetta · #7 09-02-2009, 01:17 PM

I changed all of my bulbs from the LL194 (~2.75 watts) to the LL168 (3.5 watts). Both are the same style and size. 27% more wattage doesn't sound like much, but it did make a noticable difference. Perhaps a quick fix for most until Blas figures out the real way to go.

-Dean

Blas · #8 09-02-2009, 01:45 PM

Anyone have a good photos of the back of the tach and the lighting arrangement in it? So I can give it a good think...

maxum_101 · #9 09-02-2009, 06:32 PM

so no one has a speedo with a burnt out light?
also to all who have posted , is your fuel guage just as bright as the rest of your guages?

i put in an led bulb and the look of it is great , like blas said not a yellowish color but nice and white, almost a blue color, but the peoblem remains the same the speedo cannot be swaped out to the leds

maxum_101 · #10 09-02-2009, 08:52 PM

OH CHIT....

sorry guys ITs NOT THE SPEEDO GUAGE , ITS THE RPM GUAGE.

sorry about that, the speedo guage has a bulb in the back somewhat same as the other guages, an easy swap out, its the RPM guage that has nothing on the back of it.

this is driving me nuts

also i just noticed that the amps guage is all white plastic on the back, not built like the others.

as for the fuel guage being not as bright, im going to try and cut off the end of the bulb plug to see if i can slide it in deeper to give a brighter effect.

hey blas, ur a elec guru, do they make anything as an adapter to extend the light bulb further away from the plug, an extender if you will?

Blas · #11 09-02-2009, 09:36 PM

Be careful how far you push the light socket in...read my post below...Any bulb should not project more than 1/16" beyond the back surface of the metal housing for the oil and temp gauges...

rodneym · #12 09-02-2009, 11:01 PM

When I needed to change my AMPS bulb, I noticed that it [bulb] was glued in, which nobody warned me about. Perhaps because nobody else seems to have it like that.

When I pulled it out, the glass shattered. I had to empty the big pieces, dig out the leftover glue and use a compressor to blow out the tiny bits.
If I were you, check to see if its glued. If not, pull. If it is, I would try to work something thin and sharp to cut the glue first. It'll be worth it.

PANAVIA · #13 09-07-2009, 03:57 AM

Hey there ! --

OK, so this Dim thing got me down too.

The fix I found was to update the instrument bulbs to Autometer LED based instrument lights.

You can use the stock sockets (smiths repro) and use the new LED blubs.

-- I chose green personally, but they have them in clear as well. --if you need to "dim" them back down you can color in the sides of the bulb with pentel sharpie and the light will diffuse further.

the dimmer switch on the dash is then pretty useless as LEDs are binary.

here are a couple of shots from 12-2008 when i did this.

ekrupa2 · #14 09-07-2009, 02:55 PM

Steve - those look great and appear to be a nice solution...are these the ones you bought? These fit right in the existing sockets? Thanks for any additional information.

http://www.autometer.com/cat_accesso...st.aspx?pid=27

maxum_101 · #15 09-08-2009, 09:16 AM

Quote:

Originally Posted by PANAVIA

Hey there ! --

OK, so this Dim thing got me down too.

The fix I found was to update the instrument bulbs to Autometer LED based instrument lights.

You can use the stock sockets (smiths repro) and use the new LED blubs.

-- I chose green personally, but they have them in clear as well. --if you need to "dim" them back down you can color in the sides of the bulb with pentel sharpie and the light will diffuse further.

the dimmer switch on the dash is then pretty useless as LEDs are binary.

here are a couple of shots from 12-2008 when i did this.

wow that looks great...
now how did you change the bulb in the rpm guage? also looking at your pics, your fuel guage seem less bright then the rest, do u notice that as well ? for mine seems like also.