Under Dash Wiring Mystery

[mgoldbach]

Hello, New guy here. I have a new to me 1986 C20 I am working on. Currently trying to sort out the under dash wiring. The dash lights, interior light and running lights do not work, the rest of the lights (turn signals, brake lights, head lights) work fine. I have posted a few photos of disconnected wires located under the dash. After looking closely for obvious locations where they can be connected, I am stuck with no answers. The disconnected wires are as follows;

Photo 1, This is a single orange/white wire with a connector on it that looks like it can be connected into one of the outlets above the fuses in the fuse box. I have no idea which outlet location, if this is where it goes.
Photo 2, This is three (pink, black and yellow) wires with a single female connector on the end. Located in the vicinity of the fuse box, left of the steering column. I have looked high and low and have no obvious answer.
Photo 3, This is a large green connector with an "AC" marking on it. I have no AC unit in the vicinity of the connector or where it can be stretched to. Also checked on the backside of the "climate control" switch unit and see no place to connect.
Photo 4, These are two wires (grey and brown) located in the vicinity of where the radio should be. Almost look like they could have been cut off in this location.

The 5 amp circuit in the fuse box has no power, the fuse is good. All the rest of the fuse box circuits have power and new fuses. In addition, the brown wire terminal on the newly installed light switch, has no power. I have replaced the 2 fusible links at the starter and the fusible link on the firewall. I am spinning my wheels trying to solve this mystery so any direction you might be able to provide sure would be a big help. Thanks for letting me join this forum and post this thread.

 

[justhorns]

So, you need to trace wires, or have a factory shop manual to identify these (or somebody here will help)But #3 is funny. AC makes the part. As in AC Delco that they have become. The green box is a idiot buzzer. Just throw it somewhere. Out the window, or in the bed if you are unsure. Grey wires are usually dash lights. Maybe #4 is the power to the radio and its face lighting power. Put a meter on the brown wire, and it should become hot if there is a good "radio" fuse.

 

[justhorns]

GM left wiring pigtails for options. Most likely, so of the hanging wires were for options not ordered

 

[75gmck25]

GM used the orange wiring for circuits with constant power, like the interior lights, cigarette lighter, etc. If there is a white wire near the orange, it would be connected to something that activates a device by grounding it.

For example, interior lights are on constant power from the orange, and the other side of the lights has a white wire running to the door switches that ground when you open a door.

For the others I would have to study the wiring diagram.

 

[mgoldbach]

justhorns - thanks for your replies, I will ditch the "AC" connector as you suggested. The pigtail option makes sense to me, I checked the driver's door switch and it is already connected. I plugged it into the top, far left row of connections in the fuse box. Thought it might power the dome light but no luck. Will keep trying.

 

[Turbo4whl]

The green box is a idiot buzzer. Just throw it somewhere. Out the window, or in the bed if you are unsure.

The 5 amp circuit in the fuse box has no power, the fuse is good.

This is for the dash lights, only powered if the park or headlights are on.

The dash lights, interior light and running lights do not work, the rest of the lights (turn signals, brake lights, head lights) work fine.

The headlight switch has two power feed connections and one ground. Sometimes the connection to the headlight switch heats and causes problems. One feed is fused for the dash and park lights. The headlights have their on feed, not fused. There is a breaker in the switch to protect the headlights. This can heat up over time and cause the plug connection problems.

Need to look at that connection.

 

[Jgonick]

The dash lights, interior light and running lights do not work

These all go through 20 AMP TL/CTSY fuse. Make sure you have power there and the fuse is good. From the fuse box, orange-40 wire runs to headlight switch for running lights(brn-9wire) & dashlights (grn-44 wire). From there the orange-40 runs to the courtesy light. Grn-44 wire feeds power to INSTR LPS 5amp fuse after the fuse gry-8 wire goes to dash lights etc..

Next place to look is where the orange-40 wire connects to the pull light switch.

See if your horn works- If it does- that means that area of your fuse box is getting power.

That orange wire with connector is probably for dome light. It should connect with white wire eventually and run to dome light. Another solid orange wire could be for a clock. Both plug into fuse box in a BAT (above the T/L CTSY & HORN/DM fuse & shunt)- see attachment of my fuse box

 

[Jgonick]

Photo 2, This is three (pink, black and yellow) wires with a single female connector on the end. Located in the vicinity of the fuse box, left of the steering column. I have looked high and low and have no obvious answer.

part of cruise control- goes to speed sensor

Photo 3, This is a large green connector with an "AC" marking on it. I have no AC unit in the vicinity of the connector or where it can be stretched to.

part of cruise control


maybe attachment will help with other cruise control wiring etc..

 

[Jgonick]

Photo 4, These are two wires (grey and brown) located in the vicinity of where the radio should be.

Front radio speaker wires were tan and grey


also- here is a link to the wiring diagrams

 

[Matt69olds]

The green box is the VSS (vehicle speed sensor) buffer. Don’t throw it away, you will create more headaches. Look for a ribbon cable that runs up to the speedometer. One the opposite end of the box, you will find a place for the plug with the pink, black, and yellow wires. The speed buffer converts a mechanical signal from the speedo into something the computer and cruise control can interpret. Without the speed buffer you will have no torque converter clutch or cruise control.

The orange wire is more than likely the power for the dome light. It plugs into the fuse box, the connector is keyed to fit in only the slot it’s intended to go in.

The 5 amp dash fuse won’t have power unless the parking lamps are on. And if the park lights don’t work, neither will the dash light.

The gray/tan wires are probably speaker wires.