Gray wire behind heater controls / radio....

[blindbug]

I have a gray wire that is hanging behind the heater controls / radio that USED to run to something, but I am unsure what. I believe it is related to lighting, because it supplies 12v when I pull the headlight switch out, but I am unsure where it should be going. At some point, someone has clipped it and attached it to something, but that has since been clipped as well, so now I have a crimped on butt connector that leads nowhere.

I am GUESSING that it has to do with heater control lighting? I'm not familiar enough with the night time lighting in these vehicles to know what should and should not be lit. If the gray wire goes to the heater controls, where do I connect it?

Additionally, I thought that maybe it went to the under-dash courtesy light, but when I twist the headlight switch counter-clockwise, it clicks and turns on the under-dash courtesy light. I'm assuming that the gray wire doesn't connect to the under-dash light, as that would be annoying when driving if it stayed on.

The diagrams I've looked at say that gray goes to 'Instrument LPS' but WHERE does it hook up is my question.

Any help on where this mystery gray wire should lead is appreciated. I'm sure it's a simple answer, but I just don't know where it goes.

 

[blindbug]

I always forget to include:

1986 Chevy C10 Custom Deluxe, Idiot Gauges (that work, btw)

 

[B.K. Cunningham]

in my 74, its a dimmer for my radio.

 

[gmachinz]

The only "single" grey wire Im sure about is the main climate control +12V feed from the fuse panel. The radio harness itself has a grey wire but that ultimately ties into the other greys for the dimmer circuit.

*edit*

I got ahead of myself-its a brown wire that provides power to CC unit-it has a grey connector on it tho

 

[blindbug]

The only "single" grey wire Im sure about is the main climate control +12V feed from the fuse panel. The radio harness itself has a grey wire but that ultimately ties into the other greys for the dimmer circuit.

Based on this, I am pretty certain that the grey wire I have hanging behind the dash is a dimmer circuit wire. I have an aftermarket radio, so there is no dimmer line going into the head unit, which would explain why the grey wire is not hooked up to anything. It is hanging beside the yellow wire and black wire which feed into the aftermarket radio (ignition and ground, if I recall correctly) so it makes sense that this grey wire would have originally went to the factory head unit and controlled the dimmer there.

There is no constant wire going to where the radio harness used to be, I don't believe... I had to put my constant to the fuse panel. Is there a constant going to the factory head unit? If so, what color should I be looking for?

One additional question: Since the grey wire is a dimmer control for the radio, I assume it doesn't also run as a dimmer control for another function... at least not the lead that is directly behind the heater control / head unit? Stated another way, I want to make sure this grey wire behind the head unit shouldn't run down to the courtesy light that is under the dash or to some wire on the heater control?

 

[gmachinz]

No it does not. The courtesy circuit only consists of orange and white wiring.