greg75vette

Hey guys, I've been lurking here for years as well as other forums looking for info on LSx swaps. From day 1, wiring has been my biggest concern.

Some info: 2000 firebird LS1/T56 into a '75 corvette

Thanks to all of you, I have a pretty good handle on what I need to do to the engine harness in order to make it stand alone. However, When I bought my engine not too long ago, they threw in the complete (at least I think it is) underhood harness as well which includes the fuse/relay box, headlight harness, etc. I have a pic of it below as well as a description of the circles I drew.

My question is who has used this? Was it more trouble trying to adapt it to an older vehicle (pre 1980) than it was worth? I figured I should use this since I have it and should help a bit and create (I hope) a cleaner install.

I have some wiring diagrams courtesy of the FAQ and a few other threads, but it seems to go over my head. I currently have the 2000 camaro system wiring diagram and a nicely done schematic of the relays needed to be used with the harness.

Are there any diagrams, pin outs, schematics specifically of the fuse box and this harness that are more clear? I just trying to better understand the layout of this harness and how to best utilize it with my swap. I honestly have no idea where most of the connectors go or even where to plug in power connections to the fuse/relay box. Any and all help is appreciated.

Here is the picture:

The WHITE circles are the headlights (will most likely discard)
The big RED circle is around the connectors that I disconnected from the engine harness
The YELLOW circle is specifically around C100, C101 and C105.

bjamick

iTrader: (31)

That is the body harness, used for headlights, blinkers, all the good stuff like that. It can't be used to run an engine.

greg75vette

That's nice to hear it's also known and the body harness (I searched assuming that name too). And I'm aware I can't run the engine on this alone. But I simply want to use this in conjunction with my engine harness (on the engine currently) for a more factory look and since it has relays and fuses for what I need (fuel pump, I'm running stock Fbody fans, etc). I figured I could utilize this, but can't wrap my head around it with the info I have.

I think I might figure it out with what I have, but I'm not great with wiring so I was seeing if anyone knew more than what I've seen so far.
The only people I've read using the body harness are guys swapping into an LT1 car.

bjamick

iTrader: (31)

Forget about that harness and sale it. Then buy an engine wiring harness and pcm. Use your stock wiring to control your headlights and other accessories.

Everything you need to know about wiring is all over this section. It's really not to bad once you get started. Pull out the wires you wont need, and run the wires for what you want to add.

greg75vette

That's what I'm trying to tell you: I have the full and very complete engine harness (with pcm). I also understand what needs to be done to the engine harness (or lack there of) to make it stand alone.
However, since I would still need a fuse box, relays, wiring to the fans and to the fuel pump, I figured I could possibly adapt this one. I have no intensions of using the headlight part of this harness (will be removed) or anything else of that sort.

Maybe my question wasn't clear and if so I apologize.

Has anyone used this harness in conjunction with their engine harness to complete the stand alone package that is needed to run an earlier car?

Aaron91RS

iTrader: (8)

i gutted the fuse box then readded wires and relayes I needed to it.
It was great since the stock wiring of course has the right end to just snap in to the fuse box.

So in short I used it to trip relays I added. (maf, coils, pcm, starter, fans)
But I really in no way used it in it's shown form.

greg75vette

Thanks Aaron. Ok it seems like there is hope then. I posted this on another vehicle specific forum and it seems there is a few guys that adapted it.

I was hoping for a quick reference "what each plug does" type of diagram from someone if that exists, but looks like it's up to me to just hunt down and define each plug using the system diagram. Tedious, but do-able. If I figure out anything groundbreaking, I'll be sure to post it.

bjamick

iTrader: (31)

Ok I got you know. Sorry I thought you were trying to use the body harness to run the engine lol.

As for using the fuse box, I guess you could, but I think just going to a junk yard and picking up one out of a GM would make it much easier for ya. It will have all the relays you need along with the fuses.

screaminChick-n

I am so happy that I used the body harness that came with my LS1.

That harness connects to your engine harness at C101, C105 and C102 (the ones that lay on the passenger fender in a LS1 fbody).

Another reason I wanted to do that is I didn’t want to re-pin the PCM for signals, wanted the PCM to control the starter in case of low oil pressure etc.

Any signals I want can be tapped from the above 3 connectors instead.

Yes u would have to eliminate the lights, blinkers, abs and cc circuits from that harness. But its pretty independent circuits and it should come out clean.

Since those fuse boxes contained the relays, fuses for the PCM, fuel, starter, fans that I am using...why re-invent the wheel.

I was swapping into an 82 TA, so the ign key switch connector was the same too. (Wire colors too). I ran that plug into the driver compartment thru an existing hole, I swapped the accessory voltage wire from the 82 ign key connector to this one.

If u look at your 73's firewall harness, there are a few red wires that bring voltage into your compartment for your interior fuse box which in turn powers your stock lights, horns, blinkers etc.
On my 82 it was connected to the alternator +ive terminal. Moved that over to the +ive terminal on the fuse box.

It started 1st time!!

The only down fall is more than 50% of the fuses are not being used. People have combined the 2 boxes into one. Or got a new one and replaced the 2 into one new nice looking box in the engine bay or even back where their under dash fuse box/ relay center is.

If real-estate is a premium (I would imagine in a corvette it is) you can do that.

bczee

iTrader: (12)

As screaminChick-n did, you could use the Body harness for the Fuse box and relays... just connect everything up and strip out what is not needed. Not needed as many have stated, but no reason you can not use some of the front Body harness for the wires, relays and fuses.. some of it will be plug and play, and some will be open to modify as you need it.

Get a Factory Service Manual for the wiring diagram, Alldata or have someone print out what you need to assist with the job of rewiring.

I am thinking of doing the same on my next project 02' Z28 LS1/A4 into my 71' Nova. Why not. I got the parts already !

Good luck,

greg75vette

Thanks guys! I'm glad to see I'm not smoking something too strong. I never asked for this, but when the salvage yard gave me the engine, this harness plus the complete engine harness came with it. I just asked for a complete engine harness and they, well, took it very literally.

I'm not the most handy with wiring (rather new to it) so as of now, I planned on stripping the unused sections of the harness out of the body harness, as you've suggested.
However, for now at least I want to keep the original car harness and the 'new' body & engine harness as mutually exclusive as possible. It may add a bit more (yes space is a premium) but I really don't want to screw up whats there.
Honestly speaking, I'm not quite sure where to tap power and ignition on the car for these new harnesses as of yet. I believe that's what you were driving at, screaminChick-n. I have much to learn. Unfortunately, it's basic wiring, haha.

bczee,
I have the Mitchell Repair system wiring diagram already, courtesy of the forum, do you still think it would be worth getting the a service manual?

rockytopper

I suggest you purchase the current performance stand alone fuse relay box. It is very very easy to create a diy harness and the unit is very compact. I did my first swap and frankly the wiring was the easiest part. Good luck I'd e glad to assist.
Rocky

greg75vette

rockytopper, do you mean this (at the top of the page)? If so, that's an idea. How does this plug in/connect to the engine harness? Do you know if it's water proof or does it need to be mounted in the cab?
I could always sell the body harness and buy this one, so I see it as a valid option.

bczee

iTrader: (12)

Many have just went down to Radio Shack and picked up Wire, Fues and Relays and have just wired them in as required. Using the kit or a donner fuse/relay setup will all work.
Some will just look better or be easier to wire up.. so.. the choice is your, but using the relay and fuse is a must to protect your electrical system.

69 Ghost

I have a similiar setup in my conversion and I am planning on merging my original dash harness with this harness along with the body harness at the fuse box not the relays. I do have the new steering column converted already though. If you look at this you can use it directly under the hood and just tie into the lights and you are ready to go. The nice thing about this also is a much stronger electrical system. I have some pics if you want to see them. I am in the process of adding the engine harness back in the car and this one is next in line for removal and stripping of non essential stuff. Mainly the ABS and emissions stuff.

rockytopper

Yes that is the one I used. I ask the vendor that same question about water proof. They said it is designed to be used under the hood or inside your car. It is ok to get some water as long as it is in a place that doesn't get drenced constantly then no problem. I have mine mounted on the inner fender next to the pcm. You ca nsee my location in the upper left corner of this pic

greg75vette

I like that set up. I'll have to see if I can work in this body harness. I want to go through and label everything out, see where the connections should be made and how things interact. From there I should be able to make a smart decision if it's the right move for me. If not, I'll simply sell it off and go a simpler route. I have to at least try since it was free haha.
I like what you're thinking 69 Ghost, but I think that maybe too advanced for me to completely mend the old and new harnesses together. I'll be able to inspect my wiring once the original engine is out to see if any of that should go. However, I do plan on keeping the conneciton for the headlight motors. I've heard of guys swapping out the vacuum actuators for Firebird motors, so what better way than to use the Firebird harness!

bczee

iTrader: (12)

Hey Rocky, its been a while since I have seen your engine bay.. still like your waterjet work ... I also saw a Olds like yours at Hot August Nights. painted Red like your old Sig was.. Looks good.. when are you going to get around to paint !?