Voltage issue - Gauge Cluster and wiring Questions

[greywurm]

Hey guys, eletrical issue... '71 c10 with '68 I6 TH350 (and '68 front end - i think PO wanted to make it a 68). Had the truck about a month, just going though the issues and getting her running properly.

I got tired of having to jump start the truck every other time i wanted to troubleshoot a tranny issue, so I changed projects and have been trying to figure out why she is slowly using volts. Battery will be just over 12 volts whenthe truck is off, but once she starts up it will drop below 12 volts and I can watch it lose .01 volts every 1-2 minutes. Turn the headlights on and it drops much much faster. And the headlights barely light anything up (Only drove at night once and it wasnt fun driving in the dark with dim lights on california windy mountain roads).

I've replaced the alternator, voltage regulator, ignition switch and had the battery tested (only 6 months old). The battery cables look to have been replaced shortly before I got the truck. The starter is also new if that matters. I added some grounds straps and reconnected the ones that werent reconnected after the PO swapped the v8 to the i6. I now have 1 from the chassis to block, 2 from firewall to block, 1 from chassis to battery, 1 from chassis to wheel well, 1 from chassis to cab and one from chassis to bed (last three underneath truck). I used this post to get ground strap info. Hell, I even have added a ground from the bolt that ground the regulator to the alternator.

I came at a loss of what else to do so I started tracing wires to see how everything is wired up and studying wiring diagrams. I have found some oddities that I need to investigate further, but I have some concern over my gauge cluster and its circuit board. The one time I drove at night, I noticed that the gauges didnt light up when i turned the headlights on - just added it to the list of things to check out. However, when I pull the cluster out to get a better look at the wiring, i noticed that the metal connect for the last pin (for ground according to the diagrams) was snapped off. I made an attempt at soldering some metal from a broken fuse to replace that but it didnt seem to help.

Some other related things is that the voltage meter and temperature gauge in the cluster do not work. there is an aftermarket temp gauge that does work, however I want to go back to the stock one, i just dont know if it is broken or not. The voltage needle never moves whether the truck is running, dying, or off. Also the speedo gets wirey when on the highway. The parking brake warning light is not hooked up, but is not in the cluster. Should it be?

Is there any way to salvage the cluster and circuit board or should I look into replacements? I found that i can get the printed circuit for about $50 new and have found used gauge clusters locally for $150, but who knows what does and doesnt work.

Any other ideas on where to look for the voltage loss before I start cutting up the wiring job the PO did? Which electrical system should I focus on? It seems to me that there are wiring mistakes in the ignition switch, starter, fuse panel and charging system. For example, it currently seems like the red wires from the battery, regulator, alternator, ignition and a fused black/white are all soldered together near the regulator, but I need to do some double checking on each wire.

I attached pics of the cluster with close ups of my poor solder job and the temp and voltage gauges. I have larger size pics if helps?
Thanks everyone

back of cluster


front of cluster


close up of attempt to fix broken piece


temp guage


battery gauge - plastic on right post is flayed but i think the connection is still safe


parking brake warning light and the cable that comes out of it. other wiring going into it comes from the brake sensor. not sure where this goes yet.