74 914 main wire harness modification, for running a 3.0-6 Options

[Luke M]

I have my brothers main wire harness laid out here on a table. The rear light portion needs some TLC. While I'm at it wanted to delete the under the seat relay. I know just jump the yellow wire and go. I want to clean up that whole mess of wires if possible. My question is what can be deleted and what can't? I plan on adding a few wires for the 3.0 press/temp gauge and maybe a few other spares from the engine up to the gauge cluster.

Maybe Jeff B will chime in here.... @JeffBowlsby

[JeffBowlsby]

My advice would be to don't bother with the deletions. Study the schematic for the circuits you want to delete and you will see that there is alot that is interconnected, which will then require additional repairs. And for what benefit...saving a couple pounds of wire? Also, whatever you renegineer you wil need an EE to figure things out going forward if ther are problems becasue the harness will have no accurate schematic.

[Luke M]

My advice would be to don't bother with the deletions. Study the schematic for the circuits you want to delete and you will see that there is alot that is interconnected, which will then require additional repairs. And for what benefit...saving a couple pounds of wire? Also, whatever you renegineer you wil need an EE to figure things out going forward if ther are problems becasue the harness will have no accurate schematic.

Hi Jeff,

Thanks for the reply. I plan on using color coded wires between the engine and chassis.
If I replace a wire (s) I'm going to use the same color/stripe. I kinda figured to just leave it be and jump the yellow starter wire. Looks like I'll clean things up a little and leave it be. Just wanted to do away with that relay wiring mess.

[ClayPerrine]

My advice would be to don't bother with the deletions. Study the schematic for the circuits you want to delete and you will see that there is alot that is interconnected, which will then require additional repairs. And for what benefit...saving a couple pounds of wire? Also, whatever you renegineer you wil need an EE to figure things out going forward if ther are problems becasue the harness will have no accurate schematic.

You are describing the harness in my big six. I started with the 73 harness. Then I removed unneeded circuits, re-pinned the relay board connection to work with a /6 relay board, changed the ignition switch, and turn signal switches for the six column, added 14 pin connectors to make the instruments removable without disconnecting all the wiring. I also added two circuits to provide power to the headlights so I could add relays up front.

And I never drew a wiring diagram. I need to do that one day....


Clay

[mepstein]

My advice would be to don't bother with the deletions. Study the schematic for the circuits you want to delete and you will see that there is alot that is interconnected, which will then require additional repairs. And for what benefit...saving a couple pounds of wire? Also, whatever you renegineer you wil need an EE to figure things out going forward if ther are problems becasue the harness will have no accurate schematic.

You are describing the harness in my big six. I started with the 73 harness. Then I removed unneeded circuits, re-pinned the relay board connection to work with a /6 relay board, changed the ignition switch, and turn signal switches for the six column, added 14 pin connectors to make the instruments removable without disconnecting all the wiring. I also added two circuits to provide power to the headlights so I could add relays up front.

And I never drew a wiring diagram. I need to do that one day....


Clay

Sounds like what I’d like to do with mine. I found a nos early harness so at least I can start from a known beginning and the wire is nice and pliable.

[Luke M]

My advice would be to don't bother with the deletions. Study the schematic for the circuits you want to delete and you will see that there is alot that is interconnected, which will then require additional repairs. And for what benefit...saving a couple pounds of wire? Also, whatever you renegineer you wil need an EE to figure things out going forward if ther are problems becasue the harness will have no accurate schematic.

You are describing the harness in my big six. I started with the 73 harness. Then I removed unneeded circuits, re-pinned the relay board connection to work with a /6 relay board, changed the ignition switch, and turn signal switches for the six column, added 14 pin connectors to make the instruments removable without disconnecting all the wiring. I also added two circuits to provide power to the headlights so I could add relays up front.

And I never drew a wiring diagram. I need to do that one day....


Clay

Staying with the 74 steer column but deleting the engine relay board. I got a 911 male 14 pin connector to mate with the 914 chassis harness. The fuel pump will be relocated to the front trunk so working on that wiring as well. Yes, I'll add a relay for the pump and also some oil cooler fans too.
I got the new gauges wired today so that's done. Waiting on some wire that I ordered to finish up the rest.

I also found a small red wire on the fuse panel cut. Not sure where it goes or went as I can't locate the other end of it. It looks to be a factory wire that was cut by some DAPO for whatever reason. I'll have to find a color coded wiring schematic and do some chasing. The list never ends.... (IMG:style_emoticons/default/wacko.gif)

[Luke M]

Still messing around with the wire harness here. Got most of it figured out. It needs some tlc for sure. The ground wires by the engine relay board are toast. It looks like a few wires got hot and melted together. Still trying to figure out the cut red wire at the fuse board. I did locate a good color schematic online so I need to give it a good look over. The headlight, turn signal, fog lights, and horn wires look a little rough up front too.
Guess I could always run new wires up there. Hopefully I ordered enough wire to get the job done. All wires will be color coded like the org wires. No need to panic.. (IMG:style_emoticons/default/laugh.gif)


I added a fog light switch to the dash but want it to work independently from the headlight switch. Anyone know if this rewire job will work for sure? I just want to confirm before I start cutting and adding wires for this.

Also adding a hot start relay in the engine bay someplace. I'll take a look and see where I could mount it.

[Puebloswatcop]

Still messing around with the wire harness here. Got most of it figured out. It needs some tlc for sure. The ground wires by the engine relay board are toast. It looks like a few wires got hot and melted together. Still trying to figure out the cut red wire at the fuse board. I did locate a good color schematic online so I need to give it a good look over. The headlight, turn signal, fog lights, and horn wires look a little rough up front too.
Guess I could always run new wires up there. Hopefully I ordered enough wire to get the job done. All wires will be color coded like the org wires. No need to panic.. (IMG:style_emoticons/default/laugh.gif)


I added a fog light switch to the dash but want it to work independently from the headlight switch. Anyone know if this rewire job will work for sure? I just want to confirm before I start cutting and adding wires for this.

Also adding a hot start relay in the engine bay someplace. I'll take a look and see where I could mount it.

Hey Luke,

If you are using a '74 wiring harness, the only wires shown on the schematic from fuse 8 are all Red/Blk. 1 goes to the fresh air blower indicator light, one to the fresh air blower and the 3rd to the windshield wiper switch.

Is it a plain red wire? could it be something the DAPO added in?

[Luke M]

Still messing around with the wire harness here. Got most of it figured out. It needs some tlc for sure. The ground wires by the engine relay board are toast. It looks like a few wires got hot and melted together. Still trying to figure out the cut red wire at the fuse board. I did locate a good color schematic online so I need to give it a good look over. The headlight, turn signal, fog lights, and horn wires look a little rough up front too.
Guess I could always run new wires up there. Hopefully I ordered enough wire to get the job done. All wires will be color coded like the org wires. No need to panic.. (IMG:style_emoticons/default/laugh.gif)


I added a fog light switch to the dash but want it to work independently from the headlight switch. Anyone know if this rewire job will work for sure? I just want to confirm before I start cutting and adding wires for this.

Also adding a hot start relay in the engine bay someplace. I'll take a look and see where I could mount it.

Hey Luke,

If you are using a '74 wiring harness, the only wires shown on the schematic from fuse 8 are all Red/Blk. 1 goes to the fresh air blower indicator light, one to the fresh air blower and the 3rd to the windshield wiper switch.

Is it a plain red wire? could it be something the DAPO added in?

Yes sir, you are correct. Red only wire and it looks like it was an add on by a PO.
I looked over the schematic today and sure enough it doesn't belong there.
Off it came and then I moved on to replacing some damaged wires.
I can now see why some places charge what they do for wire harnesses.
I got the engine bay to tail lights pretty much squared away. I need to install the pins into the holder. Next up is to run new wires for the headlight, fog lights and turn signals. Installing new ground wires up front as well.

Can anyone confirm the fog light switch rewire schematic I posted is correct?

[Puebloswatcop]

Still messing around with the wire harness here. Got most of it figured out. It needs some tlc for sure. The ground wires by the engine relay board are toast. It looks like a few wires got hot and melted together. Still trying to figure out the cut red wire at the fuse board. I did locate a good color schematic online so I need to give it a good look over. The headlight, turn signal, fog lights, and horn wires look a little rough up front too.
Guess I could always run new wires up there. Hopefully I ordered enough wire to get the job done. All wires will be color coded like the org wires. No need to panic.. (IMG:style_emoticons/default/laugh.gif)


I added a fog light switch to the dash but want it to work independently from the headlight switch. Anyone know if this rewire job will work for sure? I just want to confirm before I start cutting and adding wires for this.

Also adding a hot start relay in the engine bay someplace. I'll take a look and see where I could mount it.

Hey Luke,

If you are using a '74 wiring harness, the only wires shown on the schematic from fuse 8 are all Red/Blk. 1 goes to the fresh air blower indicator light, one to the fresh air blower and the 3rd to the windshield wiper switch.

Is it a plain red wire? could it be something the DAPO added in?

Yes sir, you are correct. Red only wire and it looks like it was an add on by a PO.
I looked over the schematic today and sure enough it doesn't belong there.
Off it came and then I moved on to replacing some damaged wires.
I can now see why some places charge what they do for wire harnesses.
I got the engine bay to tail lights pretty much squared away. I need to install the pins into the holder. Next up is to run new wires for the headlight, fog lights and turn signals. Installing new ground wires up front as well.

Can anyone confirm the fog light switch rewire schematic I posted is correct?

Hey Luke, can I ask where you are getting your wire from

[FlacaProductions]

One good source is https://www.restoration-design.com - I've sourced factory colored and sized wire in bulk from them in the past. Great to work with.

[Luke M]

Still messing around with the wire harness here. Got most of it figured out. It needs some tlc for sure. The ground wires by the engine relay board are toast. It looks like a few wires got hot and melted together. Still trying to figure out the cut red wire at the fuse board. I did locate a good color schematic online so I need to give it a good look over. The headlight, turn signal, fog lights, and horn wires look a little rough up front too.
Guess I could always run new wires up there. Hopefully I ordered enough wire to get the job done. All wires will be color coded like the org wires. No need to panic.. (IMG:style_emoticons/default/laugh.gif)


I added a fog light switch to the dash but want it to work independently from the headlight switch. Anyone know if this rewire job will work for sure? I just want to confirm before I start cutting and adding wires for this.

Also adding a hot start relay in the engine bay someplace. I'll take a look and see where I could mount it.

Hey Luke,

If you are using a '74 wiring harness, the only wires shown on the schematic from fuse 8 are all Red/Blk. 1 goes to the fresh air blower indicator light, one to the fresh air blower and the 3rd to the windshield wiper switch.

Is it a plain red wire? could it be something the DAPO added in?

Yes sir, you are correct. Red only wire and it looks like it was an add on by a PO.
I looked over the schematic today and sure enough it doesn't belong there.
Off it came and then I moved on to replacing some damaged wires.
I can now see why some places charge what they do for wire harnesses.
I got the engine bay to tail lights pretty much squared away. I need to install the pins into the holder. Next up is to run new wires for the headlight, fog lights and turn signals. Installing new ground wires up front as well.

Can anyone confirm the fog light switch rewire schematic I posted is correct?

Hey Luke, can I ask where you are getting your wire from

I got my wire from here. https://4rcustomswire.com/
I'm using mostly 16 & 18 G wire. They offer a GXL & TXL wire. The GXL is a better product for automotive use. They also offer high temp wire as well. Shipping is pretty quick and usually I have it in hand within 2 days.

[mlindner]

I did as Jeff said. Only removed relay board, and seat belt relay under passenger seat. All others just rapped up if ever needed again. My wire loom was all in great shape. And I'm very color blind so I could not do what you are doing. Best, Mark[attachmentid=810645)

[Luke M]

I have the wire harness pretty much wrapped up here. I just need to order more cloth tape to wrap the wires up. I want to make the headlights/fog lights mod before I put the dash/harness into the car. Can anyone confirm what needs to be done to make the fog lights come on without the headlights on? I posted a schematic about this but before I start cutting wires I'd like to know if this works.

Thanks..

[lesorubcheek]

That looks like some seriously good quality work. (IMG:style_emoticons/default/thumb3d.gif) It's also a great reminder for the need of real estate to lay out and work on harnesses.

Dan

[JeffBowlsby]

So Luke…how much time do you have in this resurrection?

[Luke M]

So Luke…how much time do you have in this resurrection?

Thanks guys.. Jeff, I have 12 days about 4 to 5 hours a day so roughly 60 hours so far. That's working on the harness, looking at schematics, and comparing my new section to the org. If you look at the pics above you can see my new section laying on top of the org harness. I also did away with the fuel pump wire in the engine bay and moved it to the front trunk. I'll add a relay up front someplace for the fuel pump and oil cooler fans. I added wires from the engine to the dash as well. Using a 911 combo gauge in dash and moved the fuel gauge to the center console. I think I'll need another 2 to 3 more hours of labor then the harness will be done. That includes wrapping the wires with cloth tape.

I also have everything written down so if there's issues later we know what's what. (IMG:style_emoticons/default/shades.gif)