Dash lights out

[i82much]

1972 K10, factory wiring:

My dash lights are out, hoping for some help diagnosing. Rear running lights work, courtesy lamp works, and the dimmer switch correctly dims some aftermarket gauges I have wired into the fuse panel.

I pulled the connector off the back of the dash and I do not have power at the #8 terminal. So if I understand this correctly, either:

(1) The gray wire is broken between the connector and the fuse panel, or
(2) Possibly I have incorrectly wired the aftermarket gauges to the hot side of the fuse and the fuse is blown.

Does that about sum it up? Assuming the gauges are wired to the cold side of the fuse, does anyone see anything wrong with simply splicing the power wire to the gauge lights into the grey wire somewhere close to the dash connector?

Thanks!

[Redline novdog]

I would google your problem on the site search,click the 67-72 button. Sounds like you're on the right track,I would not splice wires!!!!

[VetteVet]

Originally Posted by i82much

1972 K10, factory wiring:

My dash lights are out, hoping for some help diagnosing. Rear running lights work, courtesy lamp works, and the dimmer switch correctly dims some aftermarket gauges I have wired into the fuse panel.

I pulled the connector off the back of the dash and I do not have power at the #8 terminal. So if I understand this correctly, either:

(1) The gray wire is broken between the connector and the fuse panel, or
(2) Possibly I have incorrectly wired the aftermarket gauges to the hot side of the fuse and the fuse is blown.

Does that about sum it up? Assuming the gauges are wired to the cold side of the fuse, does anyone see anything wrong with simply splicing the power wire to the gauge lights into the grey wire somewhere close to the dash connector?

Thanks!

Here is how the circuit is wired.

The red wire from the firewall block feeds the headlight switch, the ignition switch, the horn relay, and the fuse panel. The orange wire on the fuse panel draws power from the red wire that feeds the fuse panel not the one that feeds the headlight switch.

The orange wire is hot all the time as long as the fuses in the fuse panel are not blown. It also feeds the dome light and the stoplight switch. Whenever you pull the headlight switch knob out it makes a connection between the orange wire and the rheostat(variable resistor), on the headlight switch, which dims the dash lights.

There is a dark green wire from the headlight switch rheostat back to the fuse panel that feeds power to the PNL LTS fuse. From there the power goes to the no.8 terminal on the cluster plug. That connection should be hot whenever you pull out the headlight switch knob. I have to ask, did you have the knob out?

To rule out the first half of the circuit, check for power on Both sides of the panel lights fuse with the knob out or where the green wire connects. Rotate the knob to be sure it shows voltage through the entire movement. If your dome light comes on then it's probably OK.

If you get power here then the first half of the circuit is good.

With the headlight switch knob pushed in, check for continuity from the other side of the PNL LTS fuse to the terminal 8 connection on the cluster plug gray wire. This will check the gray wire for opens between the fuse panel and the cluster plug.

If you have wired the ground wire for the aftermarket lights then of course it will blow the fuse and you will have to disconnect those wires and ground them and wire the hot AM lights to the gray wire or to the PNL LTS fuse.
I think most aftermarket lights only have one wire that's hot and the light body is the ground.

I hope this helps. VV

[i82much]

Thanks everyone. VV, you must have been right that I didn't have the lights on because I checked this morning and I do indeed have positive voltage at #8. Not only that, after moving things around back there a bit this morning one of my instrument panel lights, behind the speedometer, seems to have come on. So now I need to figure out why some but not all of them are on. I definitely have some new bulbs that are not coming on, but I think first I will make sure all the bulbs are new and then go from there.