I am near the end of restoring my 1971 LT1 and have a wiring problem and am definitely not experienced in auto wiring. I am installing a Dewitt's radiator with dual electric fans and converting the headlight and wiper door actuators to electric with Richard454 kits. Based on my rough calculations (correct me if I'm wrong) I will need an alternator around 100-120 amps. The only chrome one I could find that fit a Gen I SBC was 150 amp one wire alternator which is installed.

All new Lectric Limited wiring harnesses will not support that many amps so I need to know how to wire the car and new electrical accessories. I asked Claude and it said to leave the alternator connection from ;the wiring harness unconnected and run a 2 AWG wire directly from the started (positive battery cable) to the alternator and also a 2 AWG wire from the negative battery terminal directly to the engine.

Also connected to the positive battery terminal (starter terminal) run a 4AWG wire to a buss on the firewall from which to run separate circuits wit appropriate fuses and relays for the fans, headlight and wiper door actuators. The wiring could be organized with busses on the firewall so everything is clean, labeled and organized.

My question is if the above is accurate and makes sense and will work, and if so, how do the Lectric Limited harnesses for the rest of the car get power if the harness isn't connected to the alternator?

Thanks so much and if you need more information please ask.

 

C3-LT1
Do you have a wiring diagram for your new harness? What is the gauge for the leads going from the alternator output to the horn relay terminal? What gauge is the lead going from the horn relay terminal to the stater post?

Assuming you maintained the original battery leads..... then the leads going from the C3 battery is already large enough. It goes to the starter post. The negative battery post has short lead to the frame under the car.

I really think all you needed was
1) a larger gauge (smaller number - the 2AWG you got) to run from the Horn Relay terminal post to the starter post
and
2) ensure that you have protection for the above lead. Typical protection for a 2 AWG lead would be a 6 gauge Fusible Link.
and
2) ensure that the lead running from the Alternator to the Horn Relay terminal is also 2 gauge to support supplying the load.

Not sure how your ammeter is wired in your car with the new harness but typically the ammeter taps off the lead between the horn relay and the starter post. You can leave it in parallel if you already ran another lead. Ammeter may not ZERO but you'll get direction charge/discharge indication. The ammeter should already be protected by a couple of fusible links anyway.

Tell us what brand/model/number the alternator you got is? If it is a 10si or 12si derivative don't be too disappointed if it cannot maintain terminal voltage at idle. A CS-144 would be a better choice but we can figure that out once you get the wiring lined up.

Where are you are powering your Electric Rad Fans from?

 

Thanks for the response. All of the Lectric Limited harnesses are stock OEM reproductions and the wiring diagram is the same. I have the diagrams from Doc Rebuild and they are great. I don't know the gauge of the wires to the horn relay. If I understand correctly the 2 gauge from the starter to the horn relay and then 2 gauge from the horn relay to the alternator will do it. will that power the rest of the harnesses and should I leave the alternator connection from the harness unconnected?

The fans were going to be powered by a 4 gauge wire from the starter.

I'm changing from the ammeter to a voltmeter in the console gauge array..

Alternator is Powermaster Street Alternators Part #37293 from Summit. The specs say GM 10SI/10DN/12SI.

Please know that when it comes to DC automobile wiring I'm a newbie. I can easily wire a house but not a car.

 

C3-LT1
Your plan sounds fine to me.
4 gauge from the starter to the electric fans sounds good.

A couple of questions/comments though:
1. Do you have protection (fusible link or one of them big fuses) for the lead going from the horn relay to the starter post? If not, then you should make sure to get wire some in.

2. IF you are using a 1-wire alternator then you only need the main lead from the alternator output .....BUT....Wrap up and save the regulator control leads because I really suspect that 10/12 DN/SI derivative will not supply enough amps at idle if you have anything other than your electric fans. I hope it works but from my experience a 94-amp 12SI could not support my requirements.

Ensure that alternator case and the contact surfaces to the engine are clean and unpainted for good conductivity. Check to ensure that the engine block ground to the frame is nice and clean on the passenger side of the engine block. Ensure the ground lead from the negative battery terminal to the frame below the battery is nice and clean.

I hope I'm being somewhat clear.

If I found the correct alternator then your alternator output will just go directly to the horn relay bus bar.
I believe this applies to your alternator:
https://www.powermasterperformance.c...93mm-110mm.pdf

 

Again, thanks for the quick response.

The schematic displayed by Claud AI shows a 175 amp fuse between the positive battery cable (starter post) and the alternator. It also is a one wire alternator. Does the wire from the battery have to go to the horn relay before going to the alternator? What about the main large lead from the OEM harness to the alternator? Do I just wrap that as well?

You are definitely being clear. My questions are just from my unfamiliarity with auto wiring.

 

IF you look at the wiring diagram for you year you will note that there are other loads coming from that horn relay bus bar. Those need to get power somehow. I don't have a diagram for your year so I don't know what they are. I don't even know what mine are since I ran alternator output to the horn relay and left all that alone.

That 175 amp fuse should do the job. If your replacement wiring is a duplicate there should be lead(s) going to your ammeter somewhere? Have you identified those? You need to find those and isolate them if you are NOT going to use the ammeter.

I do NOT know what you mean here: "What about the main large lead from the OEM harness to the alternator? "

Are we talking about 2 different wiring systems?

 

Thanks. I'll take a picture tonight of the wire about which I'm speaking. I'll also look at the ammeter leads but I was just assuming that I would isolate them at where they connect to the gauge behind the dashboard. I'll also check what comes off of the horn relay and get back to you.

Thanks so much for your help.

 

C3-LT1

I will send you a PM.
After pondering a bit I think it would be easiest to install your new replacement harness and just tape off the ammeter leads and start from there. That way the power from the battery will be wired up to the horn relay and then we can start modifying from there.

 

I think I'm getting confused by the terminology used in this thread. I don't get the highlighted section above. If I'm not mistaken, doesn't power FROM the battery go directly to the starter via the battery cable and is really only applicable during engine starting? Once the car is running, power goes FROM the alternator TO the horn relay (and out to other loads) and then TO the starter lug and then on TO charge the battery via the positive battery cable.

 

nwav8tor
If you go take a voltage reading on your car (with the car OFF) you will note that you can read battery voltage at:
1. the battery
2. the starter post
3. the horn relay (bus bar)
4. the alternator output lug

that "path" of wiring is energized at all times.

You can verify this yourself by taking voltage reading at #3 and #4 ..... really no need to crawl under and read the starter post since that's initial connection heading forward from +battery cable.