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Old 06-18-2020, 12:40 AM   #1
koolkat
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1970 C10 wiring harness question

This truck looks like it retains most of the factory wiring. My question refers to the harness on the driver side in the engine bay, up through the bulkhead/firewall(behind the fuse block).The alternator has a large-gauge red wire coming off the back of it, which goes down to the frame and back up and meets with some other groups of wires right behind the driverside headlight. There is another large gauge red wire that seems to travel with it into the cab(rightside connector on the firewall at the top right wire). Someone cut that red wire to send it to the a/m Sunpro ammeter. I removed the fuse panel inside the cab, and found that red wire along with 2 other large gauge red wires are crimped down to 2 wires(and it looks like a factory crimp).https://ibb.co/MNL2Qkx
My question is, has anyone dealt with these wires before or know what wire they cut in the engine bay for the ammeter?https://ibb.co/w7qxMb8
Just want to be sure I can snip off the a/m ammeter wire and be fine, as I ordered some new gauges with a voltmeter(I dont need any fires in the truck)

Thanks in advance
Jeff

Last edited by koolkat; 06-18-2020 at 07:40 AM. Reason: less to read
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Old 06-18-2020, 10:59 AM   #2
RustyPile
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Re: Wiring question in a 1970 C10

Who knows after all these years and POs, what modifications have been made to the electrical system.. That red wire you described is the main power distribution wire.. It's also part of the charging system.. It goes to the battery, alternator, voltage regulator, ignition switch and fuse box.. Generally speaking, an after market ammeter of the type you describe is installed in series (not shunted) in that wire.. The wire is cut and the gauge is connected to each end of it.. More than likely, you can simply remove the ammeter and splice the 2 wires back together.. The best tool you can have when doing any electrical repairs or modifications is a proper wiring diagram.. You can find those diagrams in the ELECTRICAL forum on this site.
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Old 06-18-2020, 04:08 PM   #3
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Re: Wiring question in a 1970 C10

check out a few of these threads.



https://www.google.com/search?domain...D%3A1%3B&hl=en
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Last edited by VetteVet; 06-21-2020 at 09:10 AM. Reason: re-entered link
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Old 06-21-2020, 01:58 AM   #4
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Re: Wiring question in a 1970 C10

This link describes how those full load style amp meters work and why they can be a problem. The article refers to Dodge trucks but theory is the same. (GM discontinued that style amp meters in the early 60's) Unfortunately for you unless you pull all of the wire loom tape apart and verify what was done you may be driving on a time bomb of sorts.
I believe Rustypile is correct in that you should be able to remove the old amp meter and connect the 2 leads together and everything should work. I however wouldn't be able to stop wondering if everything the PO did was copacetic and never going to fail. Just my opinion.

http://www.madelectrical.com/electri...p-gauges.shtml

Here is a second link about Chevy wiring. The article is based on earlier car wiring and the actual wiring in our trucks is somewhat different. Like the horn relay is under the dash and not tied in directly to the main charge circuit. But it is close enough if you compare the article with our wiring diagram it will make sense.

http://www.madelectrical.com/electri...evymain1.shtml
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Old 06-21-2020, 09:12 AM   #5
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Re: Wiring question in a 1970 C10

Try the link again. It works for me and I re-entered it .
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Old 06-30-2020, 08:34 PM   #6
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Thumbs up Re: Wiring question in a 1970 C10

This should be how it's wired from the factory. All the red wires run together at some point. Most times the junction place is right behind the drivers head light. It's just a crimp connection that is wrapped in tape inside the bundle of wires. Don't worry about the drawing it for adding a newer alternator but the wiring shows the correct junction.
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Old 06-30-2020, 09:34 PM   #7
dmjlambert
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Re: Wiring question in a 1970 C10

That's not the factory wiring, that is my modification of it when installing a 12SI internally-regulated alternator with another junction block.

The stock config:
Name:  wir.jpg
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Here's the whole diagram.
http://67-72chevytrucks.com/vboard/s...49#post7809749
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Old 07-01-2020, 04:21 PM   #8
Andy4639
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Question Re: Wiring question in a 1970 C10

You didn't read my post did you. I stated it was for a newer alternator but the junction is the same.
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Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 07-01-2020, 04:41 PM   #9
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Re: Wiring question in a 1970 C10

Yes, I saw it and I'm saying the junction is not the same. In my updated diagram you show, there is an additional junction compared to the factory wiring. The factory setup does not have both of these junctions (indicated by the green arrows). Factory wiring just has the one junction with the big black dot where the red wires meet with the ammeter black/white wire.
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Old 07-02-2020, 12:16 PM   #10
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Re: Wiring question in a 1970 C10

The under dash splice you also ask about is shown in this image and it is factory. There should be a total of five wires tied together so they may have done it in two spices.

The 12R power feed from the bulkhead connector feeds the Horn Relay, Ignition Switch, Light Switch, and part of the Fuse Box. These connections will be Hot at all times.

That junction is center, left in the image. You should be able to use your browser to expand that area of the image to see it in more detail. I could have shown a close up of the splice, but i wanted to show the light switch and ignition switch.
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