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Old 11-02-2022, 04:36 PM   #1
Johnl48
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Question about wiring

I'm in the process of wiring on my restoration 70 c20
I'm using the factory harness
Positive cable to starter
Purple wire from harness to starter
Wire from positive terminal to junction block on pass fender which I assume powers the fuse block ?

My issue is I'm getting power to just a few fuses, no switched power and nothing to starter with key
Is rhere some other source to power ignition switch?
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Old 11-02-2022, 04:56 PM   #2
kwmech
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Re: Question about wiring

Should have a 12v feed to the ign switch and a working ign switch to feed the fuse block
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Old 11-02-2022, 05:06 PM   #3
Johnl48
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Re: Question about wiring

Quote:
Originally Posted by kwmech View Post
Should have a 12v feed to the ign switch and a working ign switch to feed the fuse block
Where does the 12v feed come from that one block on the fender ?
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Old 11-02-2022, 05:36 PM   #4
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Re: Question about wiring

Quote:
Originally Posted by Johnl48 View Post
Where does the 12v feed come from that one block on the fender ?
That is correct. Here's a link to some schematics that show the red wire running from the fender junction block to the fuse panel and ignition switch.

http://67-72chevytrucks.com/vboard/s...d.php?t=185856
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Old 11-02-2022, 10:16 PM   #5
franken
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Re: Question about wiring

BTW there should be a fusible link between the battery and the junction block...
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Old 11-03-2022, 06:56 AM   #6
Johnl48
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Re: Question about wiring

Quote:
Originally Posted by franken View Post
BTW there should be a fusible link between the battery and the junction block...
What size fuse should go there ?
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Old 11-03-2022, 07:19 AM   #7
Ironangel
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Re: Question about wiring

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Originally Posted by Johnl48 View Post
What size fuse should go there ?
A fusible link is a short section of sacrificial wire spliced into the various power feeds for accessories. They are usually 4 wire gauges smaller that the power wire they are designed to protect. Here's a good explanation, https://www.youtube.com/watch?v=Tg7K343N5w0&t=138s
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Old 11-03-2022, 07:25 AM   #8
Johnl48
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Re: Question about wiring

Quote:
Originally Posted by Ironangel View Post
A fusible link is a short section of sacrificial wire spliced into the various power feeds for accessories. They are usually 4 wire gauges smaller that the power wire they are designed to protect. Here's a good explanation, https://www.youtube.com/watch?v=Tg7K343N5w0&t=138s
Just wondering if I can put an inline fuse in ? Easier to change if blown
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Old 11-03-2022, 07:45 AM   #9
dmjlambert
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Re: Question about wiring

It should never blow, it only does if there is a really bad short. Normally it should last for decades. Our trucks normally have 12 guage wire as the largest unfused wiring in the truck, so to protect that you would use a piece of 16 gauge fusible link wire about 6 to 9 inches long to connect the battery to the junction block. It has a special non-flammable insulation and they are usually grey. Pieces of fusible link wire are sold in car parts stores, usually in a blister pack.
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Old 11-03-2022, 07:50 AM   #10
Johnl48
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Re: Question about wiring

Quote:
Originally Posted by dmjlambert View Post
It should never blow, it only does if there is a really bad short. Normally it should last for decades. Our trucks normally have 12 guage wire as the largest unfused wiring in the truck, so to protect that you would use a piece of 16 gauge fusible link wire about 6 to 9 inches long to connect the battery to the junction block. It has a special non-flammable insulation and they are usually grey. Pieces of fusible link wire are sold in car parts stores, usually in a blister pack.
Thank you
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Old 11-03-2022, 09:03 AM   #11
Grumpy old man
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Re: Question about wiring

This should help .

http://www.madelectrical.com/catalog/fusible-link.shtml
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Old 11-03-2022, 09:11 AM   #12
Johnl48
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Re: Question about wiring

So I'm getting power to everything except the purple wire to the starter via ignition switch. This is an automatic converted from a 4 speed. Was there a NSS with the 4 speed from factory I'm missing ? I don't see any plugs under dash for one
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Old 11-03-2022, 09:43 AM   #13
Johnl48
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Re: Question about wiring

I figured the starter issue out. Battery problem. Thanks
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