instrument cluster light switch & panel light rheostat

[dllubin]

You can splice them back together but there will be a fair amount of loss. You could replace it with 1mm solid core plastic fiber like they use for digital audio (Toslink). Or, if you've got an old C3 Corvette lying around, you can steal the 1mm fiber they used for the light monitor system. The easiest way to prepare the optical end surface is to polish it with toothpaste.

 

[tvmaster]

All of the ends of the fiber optic lines look like that. One of those is pretty long, it attaches to the headlights switch. If your taking things apart in the console, that one long line may look like something that's easier to simply cut off - and spice together later! (Hacked)
If that has happened you'll either need a new bunch of fiber optic lines, do without an illuminated headlights switch, or you could do the LED light thing on just the headlights switch. Because I don't think you can splice the fiber optic lines back together again. (Can you?)
BTW - The LEDs that you need for such a conversion would be very small - as in the same diameter of the end of that fiber optic line. They are out there - cheap.
And no, that's not #53. #53 is a very small incandescent light bulb.
I think the two yellow/red wires are 12v into the fiber optics light. One of those yellow red wires feeds 12v to #53. The yellow/black feeds 12v to the cigar lighter surround incandescent light.

That one, dangling, long line perfectly reached the upper heating panel display, so that seems solved. All the other switches have hardwired fiber-optic feeds which seem built into the plastic. The lower heating panel lettering is fed by two wires, and a combinner which was empty when my investigation started, but perfectly fits a 74 size incandescent bulb, and perfectly slots in the back of the lower heater panel. This is #53? Suppose I could throw in a LED there one day as well.

The fiber-tunnel has what appears to be TWO ends to feed a lightbulb, and there happen to be two, loose bulbs with wires long enough to reach the tunnel. After two days of searching, blowing fuses and head-scratching, I still can’t figure out where those two bulbs get power from. Somewhere, I’m thinking an alteration has been done. Tomorrow the car is off to an expert for hopefully solving some of these inherited mysteries.

I‘m thinking this bloom is? Grounds? Fiber bloom? Two have been cut, but no idea from where.

 

[ng_randolph]

he fiber-tunnel has what appears to be TWO ends to feed a lightbulb, and there happen to be two, loose bulbs with wires long enough to reach the tunnel. After two days of searching, blowing fuses and head-scratching, I still can’t figure out where those two bulbs get power from. Somewhere, I’m thinking an alteration has been done. Tomorrow the car is off to an expert for hopefully solving some of these inherited mysteries.

From fuzzy memory (I last had the console out in 2009): I believe the bulb for the fiber optic bundle gets ground from its mounting tab, so unless it is properly mounted, it will not light.

 

[kmead]

The silver barrel needs to be mounted down to get ground as Bjorn states or the bulb to get ground.

The one bulb goes into the one end and the fiber optic system plugs into the other, which is the bundle in your second to last image, unfortunately it would appear someone has cut several of the leads.

I am certain MWB or Fiat Plus will have these in stock as a used part. To replace you will need to pop the back off the switches to replace it at all positions.

Given that you are likely to need to do the above there is another option. There have been a few references here about changing to ‘rice’ LED bulbs. I think Jeff VanDyke was the first to actually build up this solution as I recall. I will have a look at finding his references.

 

[tvmaster]

The silver barrel needs to be mounted down to get ground as Bjorn states or the bulb to get ground.

The one bulb goes into the one end and the fiber optic system plugs into the other, which is the bundle in your second to last image, unfortunately it would appear someone has cut several of the leads.

I am certain MWB or Fiat Plus will have these in stock as a used part. To replace you will need to pop the back off the switches to replace it at all positions.

Given that you are likely to need to do the above there is another option. There have been a few references here about changing to ‘rice’ LED bulbs. I think Jeff VanDyke was the first to actually build up this solution as I recall. I will have a look at finding his references.

When you say ‘mounted down’ do you mean screwed to the frame? It is. Solidly. And although someone has cut two leads, every switch DOES have a good lead heading to the bundle from the looks of things. I still like the idea of using the original design if all the parts work, and by feeding the barrel with higher intensity lights, I’m hoping that works, as long as the rheostat a) still works, and b) can handle low, LED stepping values. I put a multimeter on each side of the rheostat, and slowly turned the dial. My values went from infinity to zero, and then one-by-one to a max of 10. It was like I was in ‘Spinal Tap’. Oh, sorry - ‘11’

 

[dllubin]

Mine came from the factory with a cut lead or two but all the required fibers in place. They may have been doing that as part of the manufacturing process.

 

[kmead]

Mine came from the factory with a cut lead or two but all the required fibers in place. They may have been doing that as part of the manufacturing process.

A universal part with multiple uses, modified on the line to match the actual need.

Yes the barrel being the ground needs to be screwed down. The bulb you choose to use has to have a metal body acting as ground or a brass/copper tab to touch off on it.

 

[tvmaster]

A universal part with multiple uses, modified on the line to match the actual need.

Yes the barrel being the ground needs to be screwed down. The bulb you choose to use has to have a metal body acting as ground or a brass/copper tab to touch off on it.

Okay, it’s all good news - the rheostat still works, as does the fiber tunnel. Apparently. the picture I posted of the bloom of fiber wires is supposed to be attached to the light somehow. Mr. Old Fiat guy has the center console ideograms up and running. And the cigarette lighter / extra missing bulb? There’s a piece missing from my car - the piece which holds the rogue bulb to the lighter assembly. $18 at Napa parts for a new lighter assembly with bulb holder.

 

[kmead]

Okay, it’s all good news - the rheostat still works, as does the fiber tunnel. Apparently. the picture I posted of the bloom of fiber wires is supposed to be attached to the light somehow. Mr. Old Fiat guy has the center console ideograms up and running. And the cigarette lighter / extra missing bulb? There’s a piece missing from my car - the piece which holds the rogue bulb to the lighter assembly. $18 at Napa parts for a new lighter assembly with bulb holder.View attachment 38908

You seem to be getting the hang of this thing. Congrats on the various victories. It is all about small repairs that eventually add up to a repaired and functioning car.

 

[tvmaster]

You seem to be getting the hang of this thing. Congrats on the various victories. It is all about small repairs that eventually add up to a repaired and functioning car.

I’m a little depressed I couldn’t figure the lighting thing out. Probably would have been easier to replace the starter

 

[tvmaster]

Mine came from the factory with a cut lead or two but all the required fibers in place. They may have been doing that as part of the manufacturing process.

Apparently, in the photos I put up, it shows the fibre tunnel turned sideways. Mr. Fiat repairman called me and scolded me because he said it was turned the wrong way, and he had to turn it 90 degrees so the fiber bloom would reach it. Like it was my fault or something. Whatever. Weird that he was the only one to notice (?) this. I’m thinking my bill is slowly being inflated, quickly, actually. Not to mention 10 other things. Oh well, classic cars have their downside...

 

[NEG]

Ask him up front what it’s going to cost so both of you are on the same page and there are no nasty surprises for either of you, you should set out exactly what you want him to do...

 

[tvmaster]

I don't remember exactly what it sounded like but nothing fancy. I disconnected the seat belt warning stuff as soon as I brought the car home from the dealer. The seat belt module was located high in the passenger kick panel along with a relay that enables the starter circuit. You can use that relay to take the load off the ignition switch with some minor rewiring. Fiat could have easily done it but they seemed to have no concern about that issue.

What I’d like to do is bypass the buzzer, but reconnect the ‘FASTEN BELTS’ light so it works again. However, I’m not sure how a system as old as this knows that there ISN’T a passenger in their seat, and keeps the light off if only the driver belts up. These days, passenger airbags are activated when the seat senses weight, no?
I can’t see the X 19 being that hi-tech?

 

[dllubin]

The seats have switches that close when you sit on them. That is what the wire coming out the bottom is for.

 

[tvmaster]

The seats have switches that close when you sit on them. That is what the wire coming out the bottom is for.

Cool! Higher tech than I thought they had in ‘74 - thanks I haven’t inspected under seats yet, just saw the wire attached to the retractor.

 

[tvmaster]

No, you shouldn't blow a fuse by bypassing the rheostat. The rheostats are problematic, don't really do much, and are frequently bypassed when they fail. When everything is working right the fiber optic lights tend to be dim, so even if you had a good rheostat you would likely always have it turned all the way up all the time anyway. I put a bright LED light in the fiber optic light receptacle and it works pretty good. Running small LED lights to each of the switches will produce more light at the switches, but it's a bit more complicated. If you have a complete, functioning fiber optic set, you really have a choice - use or replace with small LEDS. If your fiber optic bundle has been hacked (most likely the one to the headlights switch has been cut) it may be easier to simply replace the fiber optics with small LEDS powered from the same circuit the powers the fiber optic light.
Test for 12v at the yellow /red wire with the lights on.
BTW - the small ideogram light (#53 in the wiring diagram above) is plugged into the clear placard over the heater/vent levers.

Any idea what brand, model of LED you put in the fiber optic tunnel? I tried this today, with two, different architecture of LED bulbs ordered from ‘SuperbrightLED’, and the result wasn’t great. Three out of four function-switch lights stopped emitting any light at all. Only the cabin switch, and two central panel lights received light.
Put the incandescent bulb back in, and they all lit up.
The rheostat still kinda worked using a LED, which I didn’t expect.
Any thoughts? I was hoping for super-bright console lights, but considering the 140 lumen rating of the LED bulb, it never materialized.

 

[dllubin]

The rheostat is wired as a voltage divider so it should work with LEDs. The fiber setup uses the light off the top of the bulb. Your LED replacement may have a much different radiation pattern than the incandescent.

 

[tvmaster]

The rheostat is wired as a voltage divider so it should work with LEDs. The fiber setup uses the light off the top of the bulb. Your LED replacement may have a much different radiation pattern than the incandescent.

Ok, I’ll look into that. First time I’ve heard only a portion of the bulb is used. Maybe just a brighter, higher wattage incandescent is the way to go? There is some chatter here on different rheostats reacting differently. I must have confused mine as one that would not work.

 

[MikeHynes]

Any idea what brand, model of LED you put in the fiber optic tunnel? I tried this today, with two, different architecture of LED bulbs ordered from ‘SuperbrightLED’, and the result wasn’t great. Three out of four function-switch lights stopped emitting any light at all. Only the cabin switch, and two central panel lights received light.
Put the incandescent bulb back in, and they all lit up.
The rheostat still kinda worked using a LED, which I didn’t expect.
Any thoughts? I was hoping for super-bright console lights, but considering the 140 lumen rating of the LED bulb, it never materialized.

I bought some lights from Superbright. Their lights seemed to be good quality. I can't say the same for their website Vehicle LED Bulb Finder . They list the 1157 for the front turn signal, brake light, and tail light for your car. It doesn't use the 1157 bulb anywhere. (Later cars ('79 up) use the 1157 for the front turn signals.)
I installed the Superbright lights in the exterior positions, but used cheap made in China LEDs in the interior. (Cheap, cheap, cheap)
This is a comparison of the incandescent bulb the fiber optics use, and the LED I used.

Here is the LED mounted in the holder. Even though this LED has 5 elements, only the one on the top (arrow) lights the fiber optics. It works just as good as the incandescent bulb. And it was cheap. There are a wide variety of different LEDs that you can choose from, some that are MUCH brighter. So shop around for miniature wedge LEDs that will fit into the light mount. (Don't forget to get the polarity right.)

Here's a pic of the LEDs I used in the instrument panel. Again, cheap made in China LEDs, but so far...they are working fine.

FWIW here's a pic of the LED substitute for the fiber optics. It has little LEDs hot glued in place in their respective holders. (Note the inline resistors) These are very bright, and work well, but you have to ground each LED so it's just a bit more complicated to install.

The setup for the later cars work work pretty much the same, but their "holder/connectors" are a bit different so the same LEDs the early cars would use are adapted to those "holder/connectors".

 

[tvmaster]

I bought some lights from Superbright. Their lights seemed to be good quality. I can't say the same for their website Vehicle LED Bulb Finder . They list the 1157 for the front turn signal, brake light, and tail light for your car. It doesn't use the 1157 bulb anywhere. (Later cars ('79 up) use the 1157 for the front turn signals.)
I installed the Superbright lights in the exterior positions, but used cheap made in China LEDs in the interior. (Cheap, cheap, cheap)
This is a comparison of the incandescent bulb the fiber optics use, and the LED I used.
View attachment 39518
Here is the LED mounted in the holder. Even though this LED has 5 elements, only the one on the top (arrow) lights the fiber optics. It works just as good as the incandescent bulb. And it was cheap. There are a wide variety of different LEDs that you can choose from, some that are MUCH brighter. So shop around for miniature wedge LEDs that will fit into the light mount. (Don't forget to get the polarity right.)
View attachment 39519
Here's a pic of the LEDs I used in the instrument panel. Again, cheap made in China LEDs, but so far...they are working fine.
View attachment 39550
FWIW here's a pic of the LED substitute for the fiber optics. It has little LEDs hot glued in place in their respective holders. (Note the inline resistors) These are very bright, and work well, but you have to ground each LED so it's just a bit more complicated to install.
View attachment 39551
The setup for the later cars work work pretty much the same, but their "holder/connectors" are a bit different so the same LEDs the early cars would use are adapted to those "holder/connectors".
View attachment 39552

Superb. Thanks. I’ll look into those fiber-switch replacement LED’s.