Is that a sensor?

[Roger Zimmermann]

The '72 CdV I bought is equipped with a speedometer in miles. Since about one year, I have a speedometer in km which is more legible in Europe. To replace it, I had to remove the trim under the steering column and the upper dash. I found something I don't know its purpose; have a look at the pictures. Is that a sensor? I found nothing is the shop manual; maybe I was not looking at the right place!
From the Cadillacs from the fifties I know almost everything; I have to learn again with the cars from the seventies!

[hornetball]

Looks like an interior/instrument light socket with a plug.  Maybe it was for an option that your car doesn't have?  Should be able to track it down using wire color and a wiring diagram.

[TJ Hopland]

I too say its a light socket.   It does kinda look like that plug thing was made to fit there, looks like its got the 2 pegs and everything.   Maybe it is or was an LED that fell apart?   The option it didn't have seems reasonable too.   Maybe something like cruise control?  That had 2 lights in it.

[Roger Zimmermann]

It could be for the cruise control. I saw only one lamp during its operation when there should be a second used as "lock-in". However, this lamp has 2 wires, the one thing I ignore its purpose has only one wire. I tried to remove that black element, without success.

["Cadillac Kid" Greg Surfas 15364]

Fiber optics?
Greg Surfas

[Greg C]

could the insert be removed and replaced with a bulb for trunk latch  if you don't have that option

[Cadillac Fleetwood]

Roger,
It is not a sensor. TJ and hornetball are correct; it's a light bulb socket. GM used that plastic filler, with pegs on it, to fill the space that would ordinarily be occupied by a light bulb.  Gray wire to a light socket ordinarily indicates instrument panel/accessory illumination. If this is near the radio, I am thinking that perhaps it is the radio illumination.  I also notice that you have the AM/FM integral tape player, which may have been illuminated from within, and not required a separate bulb and socket, hence the plugged socket.  There are two bulbs to the cruise control switch, but the bulbs have black plastic sockets, and not metal ones.

-Charles Fares

P.S.  If you need a cruise control directional signal lever, send me an e-mail.

[The Tassie Devil(le)]

The factories inserted these plastic plugs into sockets that were not being used so that there was no chance of the "live" wire finding its' way out and touching a grounding surface, thereby blowing a fuse.

To remove it, one has to treat it as a lamp, and push in and twist, then pull out.

A lot of manufacturers make wiring looms to suit many options, and simply not use parts when not required.  Beats the hell out of making a different loom for every conceivable option.

In your case, Cadillac didn't require many "empty" wires, as most people would have ordered most options.

I have stripped many cars, and that includes unwrapping wiring looms and separating the wiring, and sorting out and coiling each wire up for future use, and there are lots of "empty" wires within looms.

This way, I have the correct wiring colour codes and amply sizes and lengths to repair or replace any wiring within a car, and when doing RHD conversions, and building Hot Rods, nothing goes to waste.

Bruce.

[Roger Zimmermann]

This is indeed a light socket, thanks for the hint. I could remove the black insert and effectively if the socket is hanging, the wire can come out and do a short. I did search into the shop manual; I cannot figure for which option this bulb was needed.
The wire is attached to the main harness with tape; as prior to my ownership somebody did an intervention under the dash, I cannot say if that tape is factory or not. I saw also a green wire with an unplugged connector and a cut blue wire for which I'm still unable to find to which circuit is does belong. Some more detective work!

[Big Fins]

On a '72, it may be the 'trunk open' light, a bulb indicator for the rear defroster, or a fibre optic display for the mirror thermometer.

[Roger Zimmermann]

The "open trunk" light is integrated in the warning lamps. Could be the lamp for the rear window defroster. Anyway, thanks to all for your help and hints!

[Cadillac Fleetwood]

The wiring diagram in the FSM shows ten (10) lamp sockets with a single 18-gauge grey wire.  Two are for light switch illumination, one is for ATC control illumination, four are for instrument cluster illumination, one is for radio illumination, and two are for clock illumination. These are metal lamp sockets.  Also shown is a single plastic socket with two wires, 18-gauge grey, and an 18-gauge black, labeled "accessory illumination and ground".

Charles Fares

[Matti R]

The "open trunk" light is integrated in the warning lamps. Could be the lamp for the rear window defroster. Anyway, thanks to all for your help and hints!

Hi Roger,

I have similar item near radio and guessed it must illumination for rear defroster, which is not included in my-71 as an option.

[TJ Hopland]

The plastic with the ground sounds like the one that would be for the optional thermometer fiber optic. 

What is ATC ?  automatic transmission control?   

[35-709]

Automatic Temperature Control

[TJ Hopland]

I knew it had to be something obvious that I was missing.   Was pretty sure it wasn't the rare Air Traffic Control option.   Pretty sure that was only available with the even more rare supervillain edition. 

[35-709]