[C3 Swap] Wiring Help!!!!
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Teching In
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From: PA
[C3 Swap] Wiring Help!!!! Okay. Sorry if a lot of this seems basic but I'm new to wiring and i'm getting super confused. LS1 into a '69 vette.
Trying to figure out what wires from the old harness need to still get hooked up along with the new LS1 wiring harness.
1. The picture from PSI harness only had 1 wire hooking up to the starter yet I have two...not sure if one is a motor ground? or if both hook to the large post on the starter solenoid.
(they are the two in my hand)
-From the old harness I'm showing the two large connectors and two small. I'm diving into my wiring diagram to figure them all out. Pretty sure my old solenoid had 4 posts and each one went to a different post. Not sure which ones are needed now that I only have 2 usable posts.
Trying to figure out what wires from the old harness need to still get hooked up along with the new LS1 wiring harness.
1. The picture from PSI harness only had 1 wire hooking up to the starter yet I have two...not sure if one is a motor ground? or if both hook to the large post on the starter solenoid.
(they are the two in my hand)
-From the old harness I'm showing the two large connectors and two small. I'm diving into my wiring diagram to figure them all out. Pretty sure my old solenoid had 4 posts and each one went to a different post. Not sure which ones are needed now that I only have 2 usable posts.
Thread Starter
Teching In
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From: PA
Thanks.
Yeah. I just traced back wires on my diagram and have figured out the old harness!
large red= hook up to solenoid..it goes to horn rely and eventually to ignition
large black=engine ground. might as well hook up to block.
small black= wire that went to the old coil. Leaving unhooked.
small purple= wire that goes to ignition/clutch synchro/neutral safety swith. I hooked it up to the small post on the solenoid.
BUT
I'm even more worried about the two connections from the new harness.
I was going to put them both on the large post but that means constant power all the time right?
The only two large red wires going into the fuse panel are:
-10amp fuse giving constant power to PCM
-Igntion relay which says should be switched
if they are both hooked to the large post they are both constant power right?
Yeah. I just traced back wires on my diagram and have figured out the old harness!
large red= hook up to solenoid..it goes to horn rely and eventually to ignition
large black=engine ground. might as well hook up to block.
small black= wire that went to the old coil. Leaving unhooked.
small purple= wire that goes to ignition/clutch synchro/neutral safety swith. I hooked it up to the small post on the solenoid.
BUT
I'm even more worried about the two connections from the new harness.
I was going to put them both on the large post but that means constant power all the time right?
The only two large red wires going into the fuse panel are:
-10amp fuse giving constant power to PCM
-Igntion relay which says should be switched
if they are both hooked to the large post they are both constant power right?
Thread Starter
Teching In
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From: PA
Here is a picture off PSI's website that looks like they just updated for the new harness with 2 connections.
As you can see they have two connection labeled for the starter BUT they have one that is obviously much smaller. I'm wondering if they screwed mine up and I should have one small one for the switched ignition relay to the small post on the solenoid?
As you can see they have two connection labeled for the starter BUT they have one that is obviously much smaller. I'm wondering if they screwed mine up and I should have one small one for the switched ignition relay to the small post on the solenoid?
I hate to tell you this, but with an early corvette with the ammeter it's more complicated.
If you want the original dash to work correctly, hook the constant hot up to the horn relay distribution point.. Wait, it gets worse...
Early corvettes have an ignition that only provides voltage to the coil when in run. When cranking, coil voltage is provided by the starter solenoid bypass wire. You'll need to check your ignition for a hot lead when cranking and in run. That wire goes to the "hot in run" leads.
If you want the original dash to work correctly, hook the constant hot up to the horn relay distribution point.. Wait, it gets worse...
Early corvettes have an ignition that only provides voltage to the coil when in run. When cranking, coil voltage is provided by the starter solenoid bypass wire. You'll need to check your ignition for a hot lead when cranking and in run. That wire goes to the "hot in run" leads.
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Teching In
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From: PA
I hate to tell you this, but with an early corvette with the ammeter it's more complicated.
If you want the original dash to work correctly, hook the constant hot up to the horn relay distribution point.. Wait, it gets worse...
Early corvettes have an ignition that only provides voltage to the coil when in run. When cranking, coil voltage is provided by the starter solenoid bypass wire. You'll need to check your ignition for a hot lead when cranking and in run. That wire goes to the "hot in run" leads.
If you want the original dash to work correctly, hook the constant hot up to the horn relay distribution point.. Wait, it gets worse...
Early corvettes have an ignition that only provides voltage to the coil when in run. When cranking, coil voltage is provided by the starter solenoid bypass wire. You'll need to check your ignition for a hot lead when cranking and in run. That wire goes to the "hot in run" leads.
My biggest concern now is why they sent me two of the large terminals when I'm pretty sure one needs to be tiny to be on the switched post.
Launching!
Joined: May 2012
Posts: 205
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From: Mobile, Alabama
I'm pretty sure how I have it hooked up now should work. Only wire that I'm not using is the one that used to go to the coil. Purple is still a switched wire and red is still a constant so nothing changes there.
My biggest concern now is why they sent me two of the large terminals when I'm pretty sure one needs to be tiny to be on the switched post.
My biggest concern now is why they sent me two of the large terminals when I'm pretty sure one needs to be tiny to be on the switched post.
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Thread Starter
Teching In
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From: PA
I need to do some searching I think. Everywhere I look it's showing the purple wire goes at the top small post...
Stolen from a C5 corvette post.
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Joined: May 2012
Posts: 205
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From: Mobile, Alabama
Yes it goes on the small starter lug, but you cannot get your hot in run power there for the rest of the wiring
Thread Starter
Teching In
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From: PA
If the purple is the same all that is left is the large red from the old harness which should be constant power right?
was the coil supplying power to the run accessories? That's the only different post i'm missing...
Maybe the horn rely controlled the run power to the stuff that needed it?
Launching!
Joined: May 2012
Posts: 205
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From: Mobile, Alabama
But...but...but....
If the purple is the same all that is left is the large red from the old harness which should be constant power right?
was the coil supplying power to the run accessories? That's the only different post i'm missing...
Maybe the horn rely controlled the run power to the stuff that needed it?
If the purple is the same all that is left is the large red from the old harness which should be constant power right?
was the coil supplying power to the run accessories? That's the only different post i'm missing...
Maybe the horn rely controlled the run power to the stuff that needed it?
Launching!
Joined: May 2012
Posts: 205
Likes: 2
From: Mobile, Alabama
This may be a way. No guaranty
http://www.trifive.com/forums/archiv...p/t-11431.html
Edit - or maybe not. This could be a 68 back problem. You need a meter or test light and someone to turn the key while you find a circuit that is hot in both run and start.
http://www.trifive.com/forums/archiv...p/t-11431.html
Edit - or maybe not. This could be a 68 back problem. You need a meter or test light and someone to turn the key while you find a circuit that is hot in both run and start.
Last edited by 74modified; Sep 3, 2012 at 04:50 PM.
Thread Starter
Teching In
Joined: Oct 2011
Posts: 26
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From: PA
This may be a way. No guaranty
http://www.trifive.com/forums/archiv...p/t-11431.html
Edit - or maybe not. This could be a 68 back problem. You need a meter or test light and someone to turn the key while you find a circuit that is hot in both run and start.
http://www.trifive.com/forums/archiv...p/t-11431.html
Edit - or maybe not. This could be a 68 back problem. You need a meter or test light and someone to turn the key while you find a circuit that is hot in both run and start.
I don't see anywhere that I need to give "hot in run" power to in the new fuse box...
Only the two wires here are what I was planning on adding...
1 fuel pump, 2 constant power...for some reason that they couldn't get from the solenoid...
Launching!
Joined: May 2012
Posts: 205
Likes: 2
From: Mobile, Alabama
I guess I'm not sure why I need "hot in run" stuff? the PCM looks to need constant... everything else is switched through the ignition.
I don't see anywhere that I need to give "hot in run" power to in the new fuse box...
Only the two wires here are what I was planning on adding...
1 fuel pump, 2 constant power...for some reason that they couldn't get from the solenoid...
I don't see anywhere that I need to give "hot in run" power to in the new fuse box...
Only the two wires here are what I was planning on adding...
1 fuel pump, 2 constant power...for some reason that they couldn't get from the solenoid...
Thread Starter
Teching In
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From: PA
I assume one of the two terminals they have in the photo below goes to an "ignition/run" post on certain solenoids? ...but NOT the stock LS1 solenoid...since it only had constant and start.
Everything else in the harness is already pre-wired so to get "run" power it has to be through one of the connections they provided.
The reason they are saying that a certain wire has to be hot in run and start is, itthe motor won't start if it's not that way. A wire may be hot in the run position of the switch and lose power when you go into the start position. If it does that, the car will NEVER START. I see you are confused about the term "hot in run". Hot in run and switched power are the exact same thing.
Thread Starter
Teching In
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From: PA
The reason they are saying that a certain wire has to be hot in run and start is, itthe motor won't start if it's not that way. A wire may be hot in the run position of the switch and lose power when you go into the start position. If it does that, the car will NEVER START. I see you are confused about the term "hot in run". Hot in run and switched power are the exact same thing.
I see switched as off when key is off, on when key is on.
It's been a long day, maybe it'll hit me some other day.
Wow I don't scour the board 1 day 
To answer your question, we have updated the picture in the instructions to show both Large Ring terminals (that you have a question about) go to CONSTANT POWER. Typically this is the large lug of your starter motor since that is where your battery cable is hooked to.
Regarding the starter motor wiring (to crank the engine). This must be supplied by the vehicle you are putting the engine in. Typically it consists of a purple wire from your ignition key and another constant power wire that feeds your fuse box in the vehicle. Hope this helps, if not give us a call when you have time, 732-691-6531. Thanks.
Jon
PSI
To answer your question, we have updated the picture in the instructions to show both Large Ring terminals (that you have a question about) go to CONSTANT POWER. Typically this is the large lug of your starter motor since that is where your battery cable is hooked to.
Regarding the starter motor wiring (to crank the engine). This must be supplied by the vehicle you are putting the engine in. Typically it consists of a purple wire from your ignition key and another constant power wire that feeds your fuse box in the vehicle. Hope this helps, if not give us a call when you have time, 732-691-6531. Thanks.
Jon
PSI
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Thread Starter
Teching In
Joined: Oct 2011
Posts: 26
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From: PA
Wow I don't scour the board 1 day
To answer your question, we have updated the picture in the instructions to show both Large Ring terminals (that you have a question about) go to CONSTANT POWER. Typically this is the large lug of your starter motor since that is where your battery cable is hooked to.
Regarding the starter motor wiring (to crank the engine). This must be supplied by the vehicle you are putting the engine in. Typically it consists of a purple wire from your ignition key and another constant power wire that feeds your fuse box in the vehicle. Hope this helps, if not give us a call when you have time, 732-691-6531. Thanks.
Jon
PSI
To answer your question, we have updated the picture in the instructions to show both Large Ring terminals (that you have a question about) go to CONSTANT POWER. Typically this is the large lug of your starter motor since that is where your battery cable is hooked to.
Regarding the starter motor wiring (to crank the engine). This must be supplied by the vehicle you are putting the engine in. Typically it consists of a purple wire from your ignition key and another constant power wire that feeds your fuse box in the vehicle. Hope this helps, if not give us a call when you have time, 732-691-6531. Thanks.
Jon
PSI
Awesome! I didn't know you guys were members lol.
The updated picture helped a lot when I saw that but the two large terminals made me worried so that's good they both go to constant(as I already hooked them up that way and don't want to crawl under there again lol)
But yeah, the build quality of the harness so far has been great. I wish I set it up to go into the drivers side of the engine bay but ended up having enough length and it still looked decent the way I routed it.
I had to extend my O2 sensor plugs since I'm running sidepipes but that was unavoidable since they weren't even bought/built yet when I ordered the harness.
