No power to gauge cluster main plug +12v (78K5)

[hawaiianblue78]

Hi CK5 gang, long time lurker but hoping this post can help me solve a riddle on my new 1978 K5.

None of the gauges worked when I got the truck, and the only time they ever did was when I once had power to the pink wires on the seat belt buzzer and pink wires to the cluster plug. It must have been a fluke.

Currently, I have power through all fuses and they all test good. Thinking it was the ignition switch I dropped the column and replaced that and still no power to the +12v pink wires on the cluster plug or seat belt buzzer pink wires.

The wiring diagram I have looked at 100 times and it keeps referring to splice 39 as a pink wire junction where it seems like the cluster plug gets its +12v, but I can't make heads or tails of it and a few of the wiring diagrams that I've found online don't match up color wise even though they are the correct year.

Now that I'm about to install the motor and have rebuilt the cluster and even installed a new printed circuit (thought it was that also), can anyone tell me where the junction or spot that the cluster plug gets its power from?

 

[Bent77]

Under the master cylinder is the bulk of the wires, and sandwiches the firewall to the fuses above the clutch pedal. There’s a screw that holds the 2 halves together. Disassemble the plug and reconnect it to make sure it’s seated all of the terminals and retry

there is also a plug that goes to the gages in the dash, these also can wiggle loose

 

[hawaiianblue78]

I tried unplugging and plugging back in the main bulkhead again and still no power to the pink wires, the main plug that goes into the gauges / printed circuit still has no power to the pink wires

 

[dyeager535]

I'm only working off a phone so I can't dig into the wiring diagram. But if the cluster power comes from a splice, what else is powered off the splice, and does it/they work?

And please tell me you aren't working off the (generally terrible) Haynes manual wiring diagrams.

 

[hawaiianblue78]

That's how they label it in the GM Service Manual. The pink wires run to a location that I can't seem to find.

I know those are horrible but the GM one isn't helping much either it seems

 

[dyeager535]

Can you post a screenshot? The GM ones tend to seem fairly complex on the surface, but usually not really difficult to decipher once you figure out a few things. All the variations and how pages cover certain circuits can complicate things. Make sure you are looking at the right application, although that vintage, with that circuit, I don't think there would be a huge difference in wiring even with the various options.