Lost my Fiber Optic Lights
 

I cannabalized a newer instrument cluster to replace my faulty fuel gauge. I put in the newer 5 pin outside temperature display, just because the screen looks better. It is not connected. This is this is the only wire not connected to the cluster. I thought I read that the wiring for the 4 and 5 pin connector was dedicated to the temperature display only. Does power pass through this connector to the fiber optic lights at the vents, A/C controlled and window switches? I checked the fuses. None are blown.

Not sure if the 87 has a dash light rheostat like the 123's do. But if you have knobs at the bottom of the instrument cluster try turning them. You may have inadvertently dimmed the lights, or have a bad rheostat.

87's have a rheostat. big ceramiccy looking thing. I lost my lighting on one switch for Windows. any of these switches have internal lighting?

Rheostat works fine on the instrument cluster lights. I am going to put my old temp display unit back in and see what happens. It is the only wire that is not connected to the cluster.

I wouldn't think the temp display would have anything to do with lighting. if I recall it has it's own back light and separate wiring

That's what I thought also. But, until I switched parts around on the cluster the fiber optics worked. I 'm not good with electrical issues and cannot read/comprehend the wiring diagram in the manual. Does anyone know where the fiber optics get their power from?

When you were moving wires around behind the dash, you may have pulled the Fiber Optic (FO)) connector 'hood' away from the lamp. If I recall from my late '85 SD this sits behind the Climate Control Unit.

The lamp may be working, but with the connector pulled off, there is no way for light to get into and down the FO leads. The connector just snaps back on, I think.

Hope this helps.

Thanks Jim. I was reading a post on another site. For the 123/126 cars there is one bulb that is the light source for the FO system and it is behind the CCU or the radio. I have not taken this area a part yet, but I have a new push button CCU to install. Maybe I can cure two problems at once.

Look at N40
 

AFAIK, the '87 300D (W124, OM603) does not have "fiber optic" lights like the W123 (and W126?) cars do. At least not if your '87 is like my '87.

What our cars do have is tiny individual light bulbs in all of the switches, controls, etc., all of which get their power from N40, the "Instrument Illumination Control Unit," located behind the instrument cluster. This acts as an "amplifier" so that the rheostat in the instrument cluster does not burn out due to the load of all of the little bulbs. If N40 fails (mine did) or if the fuse (#9) for its power fails, all of the lamps except for the instrument cluster will not work.

You may have pulled a connector loose when you removed the cluster to install the new temp display. N40 is bolted to a bracket alongside N2/4, the "Warning Module." N40 is the right-hand one of that pair.


http://i323.photobucket.com/albums/n...ing-Module.jpg


http://i323.photobucket.com/albums/n...lumination.jpg


Jeremy

Thanks for the picture and the direction Jeremy. I will look tonight when I get home and let you know how it goes. Is the round thing in the lower left corner the speedo cable? That's the only thing that looks familiar.

Correct.

That N2/4 thats the sucker that buzzes isnt it?

The connector to the instrument illumination control gizmo was firmly attached and I double checked fuse 9, OK. It appears my instrument illumination contol has bit the dust. I don't see this part listed anywhere. It is a PnP or dealer part?

I received the N40 gizmo and installed it, but still no lights. I checked #9 fuse again. Still good. I'm looking at the wiring diagram Jeremy posted. The power comes from the fuse to terminal 30 and then out thru terminal 58d and 58D. 31 is the ground. Tomorrow I will check the 30 socket on the wire connector for 12V. If N40 is getting 12v, then I'll try a gound wire jumper to 31.
Am I on the right track?
I tried a continuity test on the pins of my N40, but got nothing.