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2.9 to 4.0 swap electrical wiring question! PLEASE HELP?

Rhinehart5

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Ok I’m new to the ranger station have read many write ups on the 4.0 swap but first time posting.

Original Vehicle: 1992 Ford ranger STX 2.9 4x4 manual trans

donor vehicle: 1994 Ford ranger XLT 4.0 4x4 manual trans

I actually done a chassi swap left all harness intact with the motor and chassi pulled the body’s swapped them over and swapped dash harness everything plugged in and mounted all the wiring harness back to the body and firing wall starts runs drives perfectly no problems at all
ONLY thing is the computer from the donor went through on driver side and my ranger computer went through on passenger side firewall

so my question is can I splice the computer harness and leave a pigtail on the plug and extend the harness to run across the firewall to passenger side to mount the computer under passenger side dash?
There’s 39 wires total my plan was to cut the plug and leave a pigtail on the plug and just Extend the harness and color match the wires but I didn’t know if extending the wires the far would mess with any thing electrical…. May be a dumb question I’m just no Electrican and I don’t wanna mess up the computer or short anything out but I don’t know what else to do to get the computer in the cab to stay dry
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ericbphoto

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Lengthening the harness should be no problem. Make sure you verify each wire is connected right. And do GOOD soldered splices with shrink tube, preferably the kind with sealant/glue inside. Crimped butt splices will only cause trouble in the long run.
 

Rhinehart5

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Lengthening the harness should be no problem. Make sure you verify each wire is connected right. And do GOOD soldered splices with shrink tube, preferably the kind with sealant/glue inside. Crimped butt splices will only cause trouble in the long run.
Thank you! I was hoping to hear this! Anybody else have any good advice as far as actually doing the wiring? Should I go with same gauge or upgrade a gauge bigger?
 

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I would keep the wire gauge the same. It is much easier to splice same gauge wire than different gauges.

If you can get wire diagrams for both vehicles, that will help you match wires since it is possible that different colors were used for different years.

I would also wire loom the completed bundle if you can and wrap that in electrical tape to protect the wiring from chaffing and what not. This step may not be possible depending on where the wires run.
 

NakedDucks

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Why do you need to lengthen anything?

This is a plug-and play swap if you’ll swap the dash and Underhood harness....

But to answer your question....

Splicing computer wires to make them this much longer is not a good idea!!

I wouldn’t worry about it, and instead mount the computer in the 92 like it was in the 94....

Just make sure the seal on the plug is good, and use some dielectric grease to make sure the moisture stays out.

(This is how Ford did it to begin with)
 

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Why do you need to lengthen anything?

This is a plug-and play swap if you’ll swap the dash and Underhood harness....

But to answer your question....

Splicing computer wires to make them this much longer is not a good idea!!

I wouldn’t worry about it, and instead mount the computer in the 92 like it was in the 94....

Just make sure the seal on the plug is good, and use some dielectric grease to make sure the moisture stays out.

(This is how Ford did it to begin with)
It might not fit that way because of the body/chassis swapping he did. He made this statement in the first post. I haven’t done the swap he did. So I’ll take his word for it.

ONLY thing is the computer from the donor went through on driver side and my ranger computer went through on passenger side firewall
 

NakedDucks

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I get it, but each wire you cut, creates 2 splices.

And some of those splices can’t get above a certain ohm reading, or it won’t work right or will kick a code.

He’s best to find a way to mount the computer without cutting wires.
 

Rhinehart5

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Why do you need to lengthen anything?

This is a plug-and play swap if you’ll swap the dash and Underhood harness....

But to answer your question....

Splicing computer wires to make them this much longer is not a good idea!!

I wouldn’t worry about it, and instead mount the computer in the 92 like it was in the 94....

Just make sure the seal on the plug is good, and use some dielectric grease to make sure the moisture stays out.

(This is how Ford did it to begin with)
It is plug and play it stars and runs fine everything works as is. But on the 94 the computer went through the fire wall in between the fender and cab and it’s sealed off my 92 is not like that and the computer went through the fire wall inside the cab passenger side floor board
 

Rhinehart5

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It is plug and play it stars and runs fine everything works as is. But on the 94 the computer went through the fire wall in between the fender and cab and it’s sealed off my 92 is not like that and the computer went through the fire wall inside the cab passenger side floor board
I would keep the wire gauge the same. It is much easier to splice same gauge wire than different gauges.

If you can get wire diagrams for both vehicles, that will help you match wires since it is possible that different colors were used for different years.

I would also wire loom the completed bundle if you can and wrap that in electrical tape to protect the wiring from chaffing and what not. This step may not be possible depending on where the wires run.
well I’m using the harness from the 94 the only problem is that the harness on the 94 goes through the fire wall on driver side and computer mounts in between the fender and cab and is sealed off the 92 is not like the the computer runs through the fire wall on passenger side and is mounted in passenger kick panel. So all I’m needing to do is lengthen the harness so the colors all match I’m just worried that lengthening it will cause problems…

it’s hard to explain but the computer on the 94 isn’t accessible from inside the cab it is literally inbetween the cab and fender on driver side and sealed off completely and my 92 body isn’t and there’s really no room to cut a whole on driver side with the main harness round plug the clutch master cylinder the throttle cable and peddles all in the way and I can’t leave it inside the engine bay without it getting wet or moisture or dirt on it or in it
 

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It is plug and play it stars and runs fine everything works as is. But on the 94 the computer went through the fire wall in between the fender and cab and it’s sealed off my 92 is not like that and the computer went through the fire wall inside the cab passenger side floor board
I understand that. But the computer was plug was exposed in the 94 from the factory.... so it’s not gonna hurt it.

You can always get a something like a pelican case and seal it up in that if you want more protection.

Long story short, extending your harness THAT MUCH will cause you problems. EACH CUT produces TWO SPLICES, so it’s not a good idea. Even a soldered and heat shrink join isn't as good as a factory one.

(Ford Senior Master Tech here)

But all that being said, it’s your project, so build it as you see fit.
 

Rhinehart5

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I understand that. But the computer was plug was exposed in the 94 from the factory.... so it’s not gonna hurt it.

You can always get a something like a pelican case and seal it up in that if you want more protection.

Long story short, extending your harness THAT MUCH will cause you problems. EACH CUT produces TWO SPLICES, so it’s not a good idea. Even a soldered and heat shrink join isn't as good as a factory one.

(Ford Senior Master Tech here)

But all that being said, it’s your project, so build it as you see fit.
would sealing the computer in an air tight case be ok? It wouldn’t case it to over heat or anything like that?
 

Rhinehart5

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I understand that. But the computer was plug was exposed in the 94 from the factory.... so it’s not gonna hurt it.

You can always get a something like a pelican case and seal it up in that if you want more protection.

Long story short, extending your harness THAT MUCH will cause you problems. EACH CUT produces TWO SPLICES, so it’s not a good idea. Even a soldered and heat shrink join isn't as good as a factory one.

(Ford Senior Master Tech here)

But all that being said, it’s your project, so build it as you see fit.
because I thought about buying a water proof boxing and sealing it off in the box but I was afraid it would cause it to over heat
 

NakedDucks

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because I thought about buying a water proof boxing and sealing it off in the box but I was afraid it would cause it to over heat
Again.... it was exposed from the factory....

So it’s not gonna hurt to expose it again.

But if you’re that worried, you can always cut that section from your 94 can and weld it back in.....
 

Rhinehart5

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Again.... it was exposed from the factory....

So it’s not gonna hurt to expose it again.

But if you’re that worried, you can always cut that section from your 94 can and weld it back in.....
But it wasn’t exposed the plug it’s self was but the computer was in a sealed off boot inbetween the fender and cab which was completely sealed off on the 94 unlike my 92 and the 92 was inside the cab in the floor board so they was both out of the elements no water or anything and like I said I considered sealing it off in a water proof box but was afraid it would over heat or get to hot
 

NakedDucks

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Try this.....

Drive the truck and see how hot the PCM gets (it doesn’t)....

Seal it in a box. Make a vent tube if you feel safer...
 

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