I cannot seem to find the light source for the fiber optics in the AC, heater knobs, rocker switches. How do you get to the source?
This is a 1978 240d so i think it is different than automatic climate controls of later cars.
Thanks in advance.

on my '71 220D, the light for the climate controll fiber-optics is in the instrument cluster.

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1971 220D/4-speed ~250K mi. Family owned (dads side) through three generations since <5K miles.
1992 Chrysler LeBaron, 3.0V6 125K. Family owned (moms side) through three generations since new.
1977 Chevy Camaro Continual hotrod project
1970 Cadillac Sedan DeVille 472ci and nearly 19' long
1974 Fiat Spider Still needs work

Follow the fiber optics...they will converge where a single bulb illuminates them. maybe two or three bulbs...on the ACC equiped cars is on the back of the panel with the climate controls on it.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

How on earth do you find the bulb and change it?

What do you do when you accidently rip the fiber optics out of the plug at the back of the instriment cluster?
My car (76 300d) doesnt light up on the left side of the AC/heat controls... after I changed the reostat, which is how I ripped the dang thing. Sorry for the hijack, but this sucks...

~Nate

For the W123 240D


Remove the temps and fan control knobs by puling them directly out towards the rear. Give them a tug. The round knobs are illuminated by individual bulbs inside the knob. You will see the tip of the bulb after you pull the knobs off. for the rest of the panel illumination. Remove the large nuts under the temp/fan knobs. Their are three. Pulll off the defrost/floor knobs. Again just pull straight out. Then the plastic panel will come off the center consol wiht wires attached. Behind the center panel you will see the light for the spyder unit.


For the instrument cluster (W123). You must pull the whole cluster and remove the two light bulbs at the top of the cluster.

http://www.diymbrepair.com/GaugePaint/

Replace the bulbs, they are the two brown based units at the top, and reinstall the cluster.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car