Power tie in - Questions

[jbgroby]

Hi Guys,


I'm ready to tie in the small lights that illuminate the gauges, but I'm a bit confused on how and where to tie them into power, You folks got any tips? I've attached a picture of the back side of my cluster to show for reference.


I daisy chained the ground and main power, but the light will need to special because they are so small


Thanks
Jake Groby

[Culver Adams]

Hello Jake Groby and Ole GMC Truckers,

My "GMC Trucks Maintenance Manual, Models 1000-5000" (number X-6023, copywrite 1960) has an "Electrical Circuit Diagram--Series 1000 Thru 3500 With Turn Signals". (This diagram follows page 340.)

It shows the Instrument Cluster, including "Inst. Lps." which I take to mean Instrument Lamps. Instrument lamps are wired in parallel (Daisy Chained sounds more interesting). Positive (shown as 18 ga. black) goes to the 3 Amp fuse protected side of the fuse block's top most fuse, labeled in the diagram as, "Panel Lps. 3 A". Negative (shown as 18 ga. black white striped) goes to ground.

May your night lights be bright lights, and Hope that helps,

Culver Adams
Minneapolis, MN
1961 K1500 with 478 V6

[Culver Adams]

Hello Jake Groby and Ole GMC Truckers,

As I think about your request, it seems you may also be looking for tips on how to connect with those tiny wires.

Inside the cab I use crimp connectors and shrink tubing: (I see you are a shrink tubing fan yourself). (Outside the cab, I solder wires to connectors--so road salt has to work harder to make a mess of my work--and I also cover the soldered connections with shrink tubing.)

I think 18 ga. stranded copper angel hair (some call it truck wire) is a little too delicate for these trucks, so I don't add new wire finer than 14 ga. When I deal with existing 18 ga. as your instrument lamps likely have, I bundle them and/or double up the end of each, twist them and solder them together (with resin for flux) and treat the soldered wire bundle as a 14 ga. wire, connect it to my added 14 ga. wire, and continue the run to fuse panel, ground, or whatever. If a photo might make this more clear, let me know and I'll see what I can dig up.

May your night lights be bright lights, and Hope that helps,

Culver Adams
Minneapolis, MN
1961 K1500 with 478 V6

[randallgrunert]

Happy New Years Everyone at 6066. As a electrician may I add a little tip that also helps seal out any unwanted moisture. After soldering place a small drop of hot glue then place shrink tube over and shrink. While heating the shrink tube you'll heat the hot glue and this will seal both ends of the shrink tube.

[pasadenajim]

Instrument lights normally are tagged into the headlight switch which serves as an on / off switch but also as a reostat when turned clockwise or counterclockwise to dim or brighten dash lights and in some cases turn on the overhead cab light.

[Culver Adams]

Happy New Years Everyone at 6066. As a electrician may I add a little tip that also helps seal out any unwanted moisture. After soldering place a small drop of hot glue then place shrink tube over and shrink. While heating the shrink tube you'll heat the hot glue and this will seal both ends of the shrink tube.

Good idea, Randallgrunert. Hot glue is probably longer lasting than a dab of dielectric grease. Thanks for the tip.

[jbgroby]

OK, so the power leads from the lights go to the headlight switch/re-o-stat. the main power for the gauges goes to the ignition. Ok I got it now (I hope). the headlight switch did not come with any instructions or diagram for the pin connector.

The unit looks like this. any ideas where to tie in the leads? How did you fine fellows do this?

[Culver Adams]

OK, so the power leads from the lights go to the headlight switch/re-o-stat. the main power for the gauges goes to the ignition. Ok I got it now (I hope). the headlight switch did not come with any instructions or diagram for the pin connector.

The unit looks like this. any ideas where to tie in the leads? How did you fine fellows do this?

I don't know how the fine fellows who actually know what they are doing go about it: I tend to get bent up like a pretzel under the dash and start chasing wires through the maze, grateful it is only 12 Volts.

Thanks, Pasadenajim, for pointing out the obvious regarding instrument lights being tagged into the headlight switch rheostat. I've been scratching my head as to why the Maintenance Manual's Electrical Circuit Diagram shows the instrument cluster's instrument lamps being fed from the fuse block's top fuse (on the fuse's right side).

Well, after following what seems like miles of spaghetti in the electric circuit diagram, I see the other side of that fuse is fed from the light switch (contact 5) by way of a 16 ga. black wire, which I assume runs through the headlight switch rheostat (the diagram doesn't show much of the internals of the headlight switch).

On wiring the light switch: attched is a photo of the same "Electrical Circuit Diagram--Series 1000 Thru 3500 With Turn Signals" from "GMC Trucks Maintenance Manual, Models 1000-5000". I cropped and took out lots of the diagram to make it easier for me to understand the light switch wiring without getting my eyes crossed to much. If your wiring follows the original colors, it might be easy to find what goes where on the light switch. If your wiring is like mine, it will still be a hunt.

One thing that surprises me is there seems to be no fuse protection on the positive side of the wiring to the light switch. The 14 ga. red wire that feeds the light switch (contact 4) comes from a splice connected to battery plus by way of a terminal on the starter solinoid. I can't see any fuse in the path. That has me thinking about putting in a fuse or a shut off switch for some protection in case of a short.

Hope this helps,

Culver Adams

[jbgroby]

it does thanks, oh the first time is a bear......