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Old 07-01-2019, 08:51 AM   #1
EagleChief
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Help determine wires, please?

Good morning. I need a little help with some wires, if you don't mind. I do have the wiring diagram downloaded, but I can't make heads or tails out of the main connection points, or harnesses (I think) at the firewall.

1) I have 3 wires that I cannot figure out what they are for - larger purple wire coming from the firewall. It runs up across the firewall to the passenger side, then I lose it somewhere. Mainly because it's patched into, what seems like, 5 different wires, with a few others that are spliced into it. So, the wire doesn't stay purple, if that makes sense. And, it's all taped up and covered at different points. Basically, I'd like to clean it up if it's possible and run 1 wire from start to finish, eventually.

2) I have these other 2 wires that I'm curious as to what these are supposed to be for. One is pink, the other is green. Currently, they are not going to anything. They've been spliced into something at one point, but since cut and are hanging free.

The truck runs fine as it is, so it's not a huge deal. I'm just trying to start chasing a wire every once in a while to see if I can clean it up. The motor was swapped at one point to a 350 from an '88 Suburban. So, the wires have been cut and spliced and butchered up. For example, I had 1 wire that I traced from a cut end (wasn't hooked to anything), across the engine bay, to another open end. When I pulled all the tape off of it, it was actually 5 different wires at different lengths, that were all connected to make one length.

Thanks for any help you can give me with these, or point me in the right direction on the wiring diagram so I can trace them that way. I've tried looking at it, but I get confused on the different connection points at the firewall and the multiple uses of the same colors. Maybe I can figure it out if I know which connection point I'm looking at.
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Old 07-01-2019, 10:02 AM   #2
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Re: Help determine wires, please?

http://outintheshop.com/faq/wiring/w...s/image002.jpg

My guesses:
Purple: Starter. Shows a purple 12 gauge wire in the schematic.

Green: Temp gauge / switch. On the stock engine, the sender is in the driver's side head between 1 and 3.

Pink: Coil wire. Likely converted to HEI and hooked to the IGN UNFUSED position on the fuse block.
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Old 07-01-2019, 11:03 AM   #3
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Re: Help determine wires, please?

Quote:
Originally Posted by rpmerf View Post
http://outintheshop.com/faq/wiring/w...s/image002.jpg

My guesses:
Purple: Starter. Shows a purple 12 gauge wire in the schematic.

Green: Temp gauge / switch. On the stock engine, the sender is in the driver's side head between 1 and 3.

Pink: Coil wire. Likely converted to HEI and hooked to the IGN UNFUSED position on the fuse block.
Thank you. I was trying to use that diagram - even have the updated, hi-def version. But, I was confused by the purple and the orange/purple wire.

The green wire makes sense. I have an aftermarket temp gauge currently mounted. Maybe I could use that wire to hook up the stock temp gauge? Looks like I'd have to either redo the harness (which I don't know how), or buy some more green wire and solder the new line in and hook up to the temp gauge.

For the pink wire, I'm not sure if it's an HEI or not. The distributor is huge, but gray in color. Guessing I'll just terminate that wire closer to the harness and cover it up. The diagram didn't show a pink wire in that harness, so I was baffled.
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Old 07-01-2019, 04:00 PM   #4
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Re: Help determine wires, please?

The green wire with the red wire connected by the blue splicer looks more like the temp sender wire. The green wire you have circled looks like a 12 gauge horn wire.
The pink wire I agree is most likely an ignition wire.
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Old 07-02-2019, 12:39 PM   #5
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Re: Help determine wires, please?

Given the location on the bulkhead, I am still going with temp. I am looking at the location relative to the tan (20T) wire on the schematic. It appears to be the same size also, as indicated on the schematic, they should both be 20 gauge. I think the horn wire is on the right side bulkhead, and can be seen taped up next to the red wire. According to the schematic, both the red and dark green horn wire should be 12 gauge. They appear the same size in the image.

Some tests you can go. Strip a bit of wire from the end of the green wire and touch it to ground with the ignition on. It should peg the gauge hot or turn on the coolant light.

Strip a bit of the end of the pink wire and measure the voltage with the ignition on. Should be about 8V.


Something to be aware of if you are trying to get your factory temp gauge working. In 78 or so, they changed the temperature sender. It went from like 1/2" NPT to 3/8" NPT. The resistance values changed also. There is a board member who sells the 1/2" NPT senders cut down and rethreaded to 3/8" NPT. My exact sizes may be off. With this sender, you can install it in a later head, and still have your factory gauge working as intended.

EDIT: If the coil is square and on top of the distributor, it's HEI, though there are aftermarket ones with a remote coil. You can pull the cap and look for points or a module.
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Old 07-02-2019, 05:00 PM   #6
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Re: Help determine wires, please?

Quote:
Originally Posted by rpmerf View Post
Given the location on the bulkhead, I am still going with temp. I am looking at the location relative to the tan (20T) wire on the schematic. It appears to be the same size also, as indicated on the schematic, they should both be 20 gauge. I think the horn wire is on the right side bulkhead, and can be seen taped up next to the red wire. According to the schematic, both the red and dark green horn wire should be 12 gauge. They appear the same size in the image.

Some tests you can go. Strip a bit of wire from the end of the green wire and touch it to ground with the ignition on. It should peg the gauge hot or turn on the coolant light.

Strip a bit of the end of the pink wire and measure the voltage with the ignition on. Should be about 8V.


Something to be aware of if you are trying to get your factory temp gauge working. In 78 or so, they changed the temperature sender. It went from like 1/2" NPT to 3/8" NPT. The resistance values changed also. There is a board member who sells the 1/2" NPT senders cut down and rethreaded to 3/8" NPT. My exact sizes may be off. With this sender, you can install it in a later head, and still have your factory gauge working as intended.

EDIT: If the coil is square and on top of the distributor, it's HEI, though there are aftermarket ones with a remote coil. You can pull the cap and look for points or a module.
Thank you! I have them coiled up and taped right now. I am not in a huge hurry to take care of them, but it is something that I'm adding to the list. Looking at your previous post, I was able to decipher the schematic a little better. Given the locations on the schematic and the wires on the firewall, I think you're right.

I've read the stuff on the temp gauge when I was looking at hooking up my stock gauge. For now, I'm going to continue to run my aftermarket gauges.
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