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Engine wiring....

6K views 35 replies 5 participants last post by  EOD Guy 
#1 ·
Trying to wire up my new engine here..

It is a 1982 chevy C10 silverado with a carb engine and 1997 alternator.

Having trouble figuring out changes to the fire wall harness connection point.


Does anyone know what year models would be the same as 1982?

I see some "UNDER HOOD ENGINE WIRING REPLACEMENT HARNESSES"" on ebay for 1970's model cars but would those plug in to my firewall?
 
#2 ·
Or maybe just a run through of the wires that I need so I can make my own..

All I really know is

Large wire from battery + to starter.

There is a red wire running from the firewall that goes to the starter I believe.

I also have a pink wire coming from the drivers side firewall harness that goes to the coil and then back into the firewall but on the passengers side.

Then I have a red wire coming from the drivers firewall that goes to a terminal on the firewall and then to the alt.

There is another red wire coming from the firewall that goes to that same terminal then down to I think the starter.. Connected to that same wire is another wire that goes to the alt then to the firewall. There is also a black wire coming from the alt plug that goes to the firewall.
2 wires total from the plastic alt plug.
and only 1 wire on the metal alt. terminal..
 
#4 ·
Or maybe just a run through of the wires that I need so I can make my own..

All I really know is

Large wire from battery + to starter.

There is a red wire running from the firewall that goes to the starter I believe.
This is the power wire for the fuse block. It will attach to the top post on the starter where the big battery cable bolts on.

I also have a pink wire coming from the drivers side firewall harness that goes to the coil and then back into the firewall but on the passengers side.
This is 12v to the coil.

Then I have a red wire coming from the drivers firewall that goes to a terminal on the firewall and then to the alt.
This a 12V distribution block. The alternator uses this block to charge the battery and power the truck when the engine is running.

There is another red wire coming from the firewall that goes to that same terminal then down to I think the starter..
This is the accessory wire from the ignition switch. It will only be hot when the key is turned to the accessory position.

Connected to that same wire is another wire that goes to the alt then to the firewall. There is also a black wire coming from the alt plug that goes to the firewall.
These are the "sense" wires for the alternator.

2 wires total from the plastic alt plug.
The red wire is the switched 12v power source for the alternator.
The brown or black wire is the sensing wire that reads system voltage requirements to tell the alternator how much voltage to put out.

and only 1 wire on the metal alt. terminal..
This is the charge wire that runs to either the distribution block on the firewall or the top terminal on the starter.
 
#6 ·
I would test and verify each wire..... as to where it goes exactly and does each wire have continuity with another wire etc..... in other words you need to be real sure where each end of each wire goes.

To answer your questions.....

1. "There is a red wire running from the firewall that goes to the starter I believe."
This should be the fuse block hot feed or it could be the ignition switch hot feed. Disconnect the battery! Use a multi-meter (continuity setting), place one probe on the end that's at the starter and the other probe on some of your fuse slots..... you should get a beep (continuity) it’s the fuse block hot feed, if no beep, turn on the ign switch…. If it beeps, it’s ign hot feed etc…..

2. "I also have a pink wire coming from the drivers side firewall harness that goes to the coil and then back into the firewall but on the passengers side."
This should be the coil wire, it should go from the fuse block to the ignition switch, also from the fuse block thru the firewall connector to the + post on the coil. Then it should switch to a yellowish or off white wire and go to the "I" terminal on the starter solenoid (if a points type set up) If you have switched to a HEI setup you may not need this..IF the pink wire is hot in run and start - if the pink wire is only hot in run, you need the yellow wire from the “I” terminal on the starter to provide power while cranking etc…..

3. “Then I have a red wire coming from the drivers firewall that goes to a terminal on the firewall and then to the alt.”
Where on the alt is it connected? If it is connected to the charge lug on the back of the alt, then it is the charge wire. It normally ties directly to the pos post on the battery or the battery cable at the starter via the distribution terminal or a splice and from there to the battery etc…... It should be the ign hot feed or the fuse block hot feed (yes there are two hot to the fuse block one should be 14 gage and the other 12 gage)


4. “There is another red wire coming from the firewall that goes to that same terminal then down to I think the starter..”
Explained in 3 above

5. “Connected to that same wire is another wire that goes to the alt then to the firewall. There is also a black wire coming from the alt plug that goes to the firewall.”
Where does it go on the alt? If it goes to the #2 terminal on the alt pig tail, then it should be the sense wire and tells the alt to provide more or less juice depending on the demands on the electrical.
The “black” wire… should be “brown” If it goes to the #1 terminal on the alt pig tail…. It is the alt exciter wire and leads to one side of the idiot light on the dash, the other side of the idiot light should have 12v with the key on (the idiot light does not get a ground). It tells the alt to wake up and start producing juice.


6. “2 wires total from the plastic alt plug.”
Explained in 5 above

“and only 1 wire on the metal alt. terminal..”
Explained in 3 above
 
#7 ·
Thanks for the replies, I have been outside today working on this and I have made some headway..

I have run into a little confusion though. Does it make sense that the red wire from the alternator plug would be tied into the starter?

There are two red wires coming from the firewall and they are tied together, one goes to the plastic alternator plug, and the other has a "eye loom" and looks as if it goes to the starter...
I will post pictures soon but should I have only 1 wire connected to the post on the alternator?
The wire that I have on the alternator post goes to a distribution block on the firewall, but how does that charge the battery?

How many wires should be connected to the starter?
right now it looks like I have 3. Big wire to positive post on battery, wire running directly from firewall, and the wire that comes from the alternator and is tied in to another wire as well.
 
#10 ·
But on yours, you only have the large positive wire from battery and the ignition wire going to the starter...
I have the purple ignition wire that looks like it hooks to the small terminal on the starter solenoid like the diagram you posted.
But in addition to the large positive wire, I think I have a red wire(coming from the alternator and firewall) that also hooks onto the large solenoid terminal..

I hope this chart clarifies some of my blabble, I am obviously very ignorant with electrical systems.
The only experience I have would be modding my(at the time) 3 year old sons slow and boring 12 volt power wheels to a 28 volt speed monster, haha! :thumbup:
 

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#11 · (Edited)
On mine I chose to run all the electrical stuff thru a 70 amp maxi fuse. On yours it appears that all your connections are run thru the starter lug, which is ok. The issue I see with yours, is the output from the alt isn't tied directly into the pos post of the battery, it appears that it's feeding the fuse block and then doubling back to the battery via the fuse block battery feed.

I don't think I'd do it that way. IMO the output wire from the alt should be tied directly to the pos post on the battery with the shortest run of wire (that's cosmetically pleasing) or to the starter lug to the pos battery cable. As far as the wires you have on the distro block..... IMO .... What do they do? I'd figure out what they were connected to on the inside of the fuse block and if possible I'd eliminate them, if they are tied to circuit/fuse lugs on the inside of the fuse block.... I'd tie them into your existing fuse block feeds splice.
 
#14 ·
I have seen people run the red wire from the alternator plug right to the alt. stud then run a 4 guage wire from the alternator stud directly to the post on the battery but that is definitely not how I was set up before.. I really should have marked everything because it has been years since I pulled the old engine.

So a continuity tester will test connections without the battery being installed?
 
#16 ·
IMO running the output from the alt directly into your fuse block isn't a good idea. Your alt can produce as much as 15 volts on a routine basis and in your application, it's dumping it directly into your electrical system via the fuse block connection, might not hurt a thing but.........

Running it thru the battery first allows the battery to act as a buffer of sorts..... the battery evens out those spikes and over charging etc..... much better way..... IMO.
 
#19 ·
Ok...gauge 4 wire from the alternator post directly to the positive terminal on the battery... But how? I have a dual post battery.. Can i simply run the top post to the starter and the side post to the alternator? I could cut my current battery cable and use a bolt down wire clamp to attach both to the same post also. Where should i put inline fuses?
 
#21 ·

Charging the battery through the starter post will work just fine. I marked up your drawing with a set up that will work well for your situation.
Clean up your fuse box and determine what all of your wires are and where they are running.
There should be only one wire powering the fuse block from the distribution block. (10ga red)
Run the sense wire to the distribution block. There should be no other wires spliced or tied into the sense wire.
Mark
 
#22 ·
Thank you guys very much,

I have made some good progress today, I got all of my grounds figured out, hooked up up the battery, and turned the engine over. The starter sounded smooth and my acc. were all working...

I have yet to hook anything up to the alternator but that is my project for tomorrow morning. :D
 
#24 · (Edited)
10ga will work fine. If you want to do some reading and get some insight check out this site. TONS of usable info here.
MadElectrical.com - Electrical Tech

This is the distribution block I installed in my '56 wagon when I rewired the front of the car this summer.

It is wired just like I marked up in your drawing. Works fine.
Mark
 
#27 ·
Okay thanks, I tested the dist block and it is in fact already hot without the alternator being hooked up to anything..

The yellow wire goes to another fuse or something and then to my tailights, The red wire going towards the passenger side is for AC stuff and the red wire coming from the drivers side is coming from the fuse panel.
If I were to go straight to the battery from the alternator what gauge wire should I use?
 

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