74 TA Dash lights stopped working- help

[74 Trans Am]

My 74 TA had working dash lights a few days ago, before I removed the old stereo and installing a new one. I did run a new 4-gauge wire to the trunk thru the dash grommet, down the driver's door sill.

Now my cluster dash lights, gear shifter plate light, and fuel/volt cluster illumination lights do not light when the headlight switch is activated.
So, my headlights, parking lights, and vanity lights work fine. I searched for loose grounds and checked all glass fuses and found no issues. I removed the bulb in the fuel/voltmeter combo and found 0 voltage on the light lead. I checked the housing, and it was continuous to ground.

I replaced the headlight switch and replaced the gauge panel circuit board (film), replaced all the bulbs and still have no dash lights. What am I missing? Appears no voltage to the dash bulbs. Attached are photos of the headlight plug. Does anyone know which wire outputs to the dash lights? From the headlight plug there is white, red, green, blue, brown, and brown w white stripe. Which one goes to the dash lights?

I installed the stereo using the harness radio wire and another constant power wire I ran directly to the fuse box, and the stereo functions properly.

Any other items to check? I do not have the metal strap on the upper left of the gauge panel from the headlight to the pod. However, the dash lights worked initially without it. I tried jumping a ground in and nothing changed....

 

[Aus78Formula]

You checked the dash illumination fuse? I think it's the tiny short 4A or similar by itself. Might have just been spiked setting up.

 

[74 Trans Am]

Yes, all fuses are good.

 

[Aus78Formula]

Might have to trace a few wires on the rear of gauge cluster. Many gauges use the grounds so assume its ok if they are working, stereo has lighting that works? Check condition of circuit board on rear in case it zapped somewhere or has a crinkle. Got a wiring diagram? Check the rheostat on headlight is working, turns gauge light dimmer up or down or cabin lamp on with doors shut.

 

[74 Trans Am]

Might have to trace a few wires on the rear of gauge cluster. Many gauges use the grounds so assume its ok if they are working, stereo has lighting that works? Check condition of circuit board on rear in case it zapped somewhere or has a crinkle. Got a wiring diagram? Check the rheostat on headlight is working, turns gauge light dimmer up or down or cabin lamp on with doors shut.

Thanks for the input. I changed the headlight switch and circuit board with no success.

 

[Aus78Formula]

Did you add any LEDs to gauges that may not have gone back in same way?

 

[74 Trans Am]

Did you add any LEDs to gauges that may not have gone back in same way?

no LEDS added. They have limited dimmability.

 

[Aus78Formula]

Double check your 4A fuse.
Did you hook stereo lights to it as well, might have opposite polarity, or just does its own thing, not dimmable.

 

[74 Trans Am]

My 74 TA had working dash lights a few days ago, before I removed the old stereo and installing a new one. I did run a new 4-gauge wire to the trunk thru the dash grommet, down the driver's door sill.

Now my cluster dash lights, gear shifter plate light, and fuel/volt cluster illumination lights do not light when the headlight switch is activated.
So, my headlights, parking lights, and vanity lights work fine. I searched for loose grounds and checked all glass fuses and found no issues. I removed the bulb in the fuel/voltmeter combo and found 0 voltage on the light lead. I checked the housing, and it was continuous to ground.

I replaced the headlight switch and replaced the gauge panel circuit board (film), replaced all the bulbs and still have no dash lights. What am I missing? Appears no voltage to the dash bulbs. Attached are photos of the headlight plug. Does anyone know which wire outputs to the dash lights? From the headlight plug there is white, red, green, blue, brown, and brown w white stripe. Which one goes to the dash lights?

I installed the stereo using the harness radio wire and another constant power wire I ran directly to the fuse box, and the stereo functions properly.

Any other items to check? I do not have the metal strap on the upper left of the gauge panel from the headlight to the pod. However, the dash lights worked initially without it. I tried jumping a ground in and nothing changed....

Update: I found the illumination 4 amp fuse blown. It had fooled me on testing as a continuity test showed that it was continuous. Turns out, the left side of the fuse is shorted to ground somewhere (grey wire). The right side gets 12.5v when the parking lights are activated.

So, since I'm getting 12.5v to the right side of the fuse, but blowing the fuse, when connected. I have a short on the "gray wire" somewhere to the dash. Dash, gauges, somewhere. I'll unplug the gauge pod and see if its still shorted out. I'm getting closer. Feel free to point out any known possible short out points troubleshoot.

 

[74 Trans Am]

Problem found! The last person to install the stereo used the grey wire as a ground wire. It does show conductivity with ground, however, if you ground the grey wire, it shorts out the dash lights, pops the fuse and no dash lights. Everything is working now, thanks everyone for the suggestions.