When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've been searching the internet forever trying to find how to look up the original alternator wiring in our LS Swap with no luck. It looks like the original voltage regulator was taking out and the alternator upgraded before. We now have a 5.3 truck motor with a 1 wire alternator. The original two plug wire has a white wire connected to a brown wire, and a red wire that plugged into the alternator. There is a green wire and a red wire that were cut previously. There is a black wire with a ring connector that was bolted to the alternator before. We wired the new LS motor standalone but are using the original wire harness for the starter. Currently nothing happens when I try to start the car. With that said, the horn doesn't work so I believe I just need to power one of the original wires. Any suggestions would be great! This is a car I bought for my son (his dream car) and am doing my best to teach him how to work on cars. Throwing an LS Swap in the mix has been troubling since I never did one.
It's been a while since I did my LS swap but here's what I remember.
LS alternator heavy wire from the starter stud around the front of the engine to the power stud on the back of the alternator. My aftermarket harness had the single wire plug into the back of the LS alternator.
If I recall correctly I then ran a some large gauge wire from the alternator stud to the horn relay like the stock setup which powers up the rest of the car. I added a in-line 40 amp maxi fuse to that wire.
You don't need to ground the alternator.
I think the brown and white wire can go away. Search wiring harness for references.
No luck. The horn relay has an orange, green, and black wire. The orange wire is always hot. From what I can tell this is part of the factory alarm system. The odd thing is when I run a jumper from the green wire by the alternator, to the positive, I can hear the relay click when the horn button is pressed. However, the horn doesn't go off. I did test the horn and it is working fine. I have a second horn in the inner driver side fender that is the alarm. My only thought now is to bypass the security system?
A true one wire alt can do away with the white and brown wires as you stated. The main power lug to the starter should power up a wire there as well and energize the car. You really need a 78 wire schematic. There was a member here that would send you a digital copy.....you might ask Wilcox if he would be kind enough to send you a digital copy. I remember the horn relay being an electrical hub/junction for things but can't remember all that was hooked to it......
Good deal. I finally found the issue yesterday. The fuse block wasn't screwed down all the way! Maybe that's why Bubba sold us the car. One minute the horn would work, one minute the lights wouldn't work. Pain in the butt! Didn't discover the issue until someone noticed the headlights going on an off while I was under the dash. Thanks for the help! Now I need to tackle some other issues and hopefully can try to start it in a few days.
1978 5.3 LS Swap
