Ignition switch wiring help

[AZKen]

Your drawing of green is what the 1964 diagram says. So you can hook the dangle up to GND or cap it off. Your choice. In 1963, 1964, 1964, GMC could not make up it's mind about idiot light or gauges. Bulb check and various circuits. It's all the same result. I think you have the info now. It makes no difference if you hook it up or not if you wiring is per factory diagram. If you don't hook it up, it will only take a few miles to see if temp gauge works. I think the idea was to see it spike to hot while cranking, for confirmation. Try it with and without the hookup to see.

[Jethro]

You guys are great! I have the answers now to just exactly what I need to know. Thanks!

My truck does have the light green wire to the 4-pin panel connector but it ends right there. No wire in the cluster harness and an empty L pin.
Earlier in my adventures I found the temp sensor wire connected to the coil +. Maybe what fried the printed circuit? Pretty sure everything under the hood is right now. Went thru the park/turn lights too.
I just fixed the panel and don't want to fry this one.
I think I'll try it first just to check the gage and then run it unhooked. It seems redundant.

I rewrapped some of my harness with the original. The rest I used the plastic loom stuff and just taped the ends and a couple other wraps just to keep it closed. The fuse block is really rough. I'm looking for some replacement terminals. Or a used block. Either that or I'll have to install a more modern chip fuse block.

[Jethro]

[AZKen]

Yes, that 20 L.GR 36 is shown dead ended on both ends. Not used.

Your fuse panel terminals are pretty rusty. I have actually sand blasted those terminals carefully and with the appropriate pressure to not destroy other areas of it. It would have to be removed to do that. If you are going to remove it to replace it, try that first. There are possible chemical rust removers that may not attack the plastic during a soak.

This is a good idea that you may find a way to use. By Edd China. Starts at around 9:45 https://www.youtube.com/watch?v=LzxeK6yp4hQ

[Jethro]

Some of the terminals are missing and some rusted completely away. I think I might be able to use one from a 66 Chevy I have with a bit of work. I'll be out of town for the weekend but I will be back to working on it as soon as possible.
That vinegar trick looks handy.
Got any tips on easy ways to get grommets in and out of firewalls?

[AZKen]

Soap and push. Soap and pinch inward. Assume you mean rubber grommets. If old and cracked, Nuclear option.

[Jethro]

Yep. Rubber grommets. Every time I have to do one I think there must be an easier way.

Update; There is a 66 Chevy project in my garage. When I saw the condition of the fuse panel in the GMC and didn't have any luck finding rebuild parts I decided to crawl in the Chevy and compare. The panels look alike.

Since I was out of town for a long weekend I didn't have a chance right away to go further. Monday I pulled the Chevy harness and sat down to pick thru and compare it to the 64 GMC diagram. At the core the 2 harnesses match. The 66 Chevy just had some extra wires added in.

Last night I pulled both harnesses apart and used the best stuff to build one for the GMC. I still have a few wires to repair before I can put her all back together but I am confident it's going to work out well. I'll let you know.

Thanks again for the advice.
And a special thanks for the diagram. I looked all over and couldn't find the right one.

[Jethro]

WooHoo!!! She's back alive!

Thanks, AZKen, for that vinegar trick. I used it on all of my connector terminals. Worked great!
Not so much on the fuse clips. Those I just scraped with a needle file.

This "ignition switch replacement" sure did snowball. I'm glad tho because now I know the whole cab is wired right if nothing else. I plan to finish cleaning up and fixing the wiring to the lights too. Already did the engine harness.