• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

2.9 to 4.0 swap electrical wiring question! PLEASE HELP?


Rhinehart5

New Member
Joined
Nov 16, 2021
Messages
11
Reaction score
0
Points
1
Location
Arkansas
Vehicle Year
92
Make / Model
Ford ranger
Transmission
Manual
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...
Ok sorry I was unaware like I said in my original post I’m no electrician and i wasn’t sure what to do hence the reason I came to this page to ask for help. I just don’t wanna ruin my computer
 


NakedDucks

Active Member
Ford Technician
Joined
May 25, 2020
Messages
337
Reaction score
63
Points
28
Location
B’ham AL
Vehicle Year
94
Make / Model
Ranger
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
No problem. And if it comes down to it, I have another computer.

But cutting wires to a PCM and extending them around 5 feet is NOT a good idea!!
C2F4E88D-E28F-4388-882A-F58D84A6E57D.jpeg
 

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
15,216
Reaction score
16,352
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.

fastpakr

Forum Staff Member
TRS Event Staff
TRS Forum Moderator
Supporting Member
Article Contributor
U.S. Military - Veteran
V8 Engine Swap
TRS 20th Anniversary
TRS Event Participant
Joined
Aug 6, 2007
Messages
7,993
Reaction score
2,797
Points
113
Location
Roanoke, VA
Vehicle Year
1999
Make / Model
Ford
Engine Type
V8
Engine Size
5.0
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
285/75-16
Especially using butt splices like that.
Exactly. I don't have any concerns about properly extending a harness as needed with good soldered and sealed connections. Butt splices are asking for disaster.
 

NakedDucks

Active Member
Ford Technician
Joined
May 25, 2020
Messages
337
Reaction score
63
Points
28
Location
B’ham AL
Vehicle Year
94
Make / Model
Ranger
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Exactly. I don't have any concerns about properly extending a harness as needed with good soldered and sealed connections. Butt splices are asking for disaster.
Even a soldered connection isn’t good in this case. Extending a harness for around 5 ft (about what he would need to extend it to be) creates 2 soldered connections (resistance) in the circuit... also, the thickness of wire will NEVER be the same as the original.... same gauge, yes, but even then, thicknesses vary.... and you again create a flow rate problem...

It’s best not to cut and extend it in this situation.
 

fastpakr

Forum Staff Member
TRS Event Staff
TRS Forum Moderator
Supporting Member
Article Contributor
U.S. Military - Veteran
V8 Engine Swap
TRS 20th Anniversary
TRS Event Participant
Joined
Aug 6, 2007
Messages
7,993
Reaction score
2,797
Points
113
Location
Roanoke, VA
Vehicle Year
1999
Make / Model
Ford
Engine Type
V8
Engine Size
5.0
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
285/75-16
I'm sorry, but that's nonsense.

Put in two good connections and the change in resistance is minimal.

Use good 18 gauge wire and the added resistance is in the hundredths of an ohm over several feet.

This isn't rocket science.
 
Last edited:

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
15,216
Reaction score
16,352
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.
I'm sorry, but that's nonsense.

Put in two good connections and the change in resistance is minimal.

Use good 18mm wire and the added resistance is in the hundredths of an ohm over several feet.

This isn't rocket science.
I agree. The resistance change would be negligible. And since those conductors are carrying such little current, it really wouldn't matter.

Since he has two harnesses, I would scavenge wire from the extra harness to make the extra length, keeping the connector pins on thos pieces. That way, I'm only making one soldered connection per conductor. I would have complete faith in it.
 

NakedDucks

Active Member
Ford Technician
Joined
May 25, 2020
Messages
337
Reaction score
63
Points
28
Location
B’ham AL
Vehicle Year
94
Make / Model
Ranger
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
I agree. The resistance change would be negligible. And since those conductors are carrying such little current, it really wouldn't matter.

Since he has two harnesses, I would scavenge wire from the extra harness to make the extra length, keeping the connector pins on thos pieces. That way, I'm only making one soldered connection per conductor. I would have complete faith in it.
If you and Fastpakr feel comfortable doing it, then by all means.... do it.

But PCM’s, ECU’s, TCM’s, BCM’s and thing like that DO in fact measure reference voltages, voltage drops, ohms, and ohm drops..... and when they see problems, they lock codes, shut down systems, and respond poorly (if at all).

One bad soldered joint, and your chasing your tail for HOURS to find it.

Is it possible? Yes.
Safe? If done right... yes
Would I do it to a major controlling module? No.
 

fastpakr

Forum Staff Member
TRS Event Staff
TRS Forum Moderator
Supporting Member
Article Contributor
U.S. Military - Veteran
V8 Engine Swap
TRS 20th Anniversary
TRS Event Participant
Joined
Aug 6, 2007
Messages
7,993
Reaction score
2,797
Points
113
Location
Roanoke, VA
Vehicle Year
1999
Make / Model
Ford
Engine Type
V8
Engine Size
5.0
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
285/75-16
If you and Fastpakr feel comfortable doing it, then by all means.... do it.

But PCM’s, ECU’s, TCM’s, BCM’s and thing like that DO in fact measure reference voltages, voltage drops, ohms, and ohm drops..... and when they see problems, they lock codes, shut down systems, and respond poorly (if at all).
Did you read this entire thread and somehow come to the conclusion that you were the only person intelligent enough to know that?
 

Rhinehart5

New Member
Joined
Nov 16, 2021
Messages
11
Reaction score
0
Points
1
Location
Arkansas
Vehicle Year
92
Make / Model
Ford ranger
Transmission
Manual
Thst
I'm sorry, but that's nonsense.

Put in two good connections and the change in resistance is minimal.

Use good 18mm wire and the added resistance is in the hundredths of an ohm over several feet.

This isn't rocket science.
that’s what I planned to do was buy new wire same gauge and solider it together and use shrink wrap and the connections and run approx 5 foot to opposite side of the cab and solder the pig tail of wires to the computer plug and shrink wrap and then use lume snd snd electrical tape to make it look nice and run along the firewall because the computer on my 2 trucks neither one is exposed to rain or water or the elements like the nakedducks guy is saying and I’m worried about it getting hit if I seal it up in a small air tight box but he’s got me worried I’m gonna screw up the computer and have problems extending the harness
 

Rhinehart5

New Member
Joined
Nov 16, 2021
Messages
11
Reaction score
0
Points
1
Location
Arkansas
Vehicle Year
92
Make / Model
Ford ranger
Transmission
Manual
Thst


that’s what I planned to do was buy new wire same gauge and solider it together and use shrink wrap and the connections and run approx 5 foot to opposite side of the cab and solder the pig tail of wires to the computer plug and shrink wrap and then use lume snd snd electrical tape to make it look nice and run along the firewall because the computer on my 2 trucks neither one is exposed to rain or water or the elements like the nakedducks guy is saying and I’m worried about it getting hit if I seal it up in a small air tight box but he’s got me worried I’m gonna screw up the computer and have problems extending the harness
Hot not hit sorry autocorrect
 

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
15,216
Reaction score
16,352
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.
Ok. Here are the numbers.

18 gauge wire; resistance is 5.8 - 7.8 ohms per thousand feet. So, adding 5 ft of wire increases the circuit resistance by 0.029 - 0.039 ohms depending on temperature.

16 gauge wire; resistance is 3.7 - 4.9 ohms per thousand feet. So, adding 5 feet of wire would add 0.0185 - 0.0245 ohms depending on temperature.

I really doubt that the ecu circuits are sensitive enough to detect that. Your multimeter definitely is not. Make good clean solder joints and use heat shrink with sealant in it to keep moisture our.

If that feels like to much risk, just use the short harness and put the ecu in a waterproof box. It's all up to your comfort level and budget.

To put that in perspective, if a sensor circuit is running 30mA (0.03amps), then at about 0.035 ohms, your wire extension has dropped the voltage by 0.00105 volts.
 
Last edited:

NakedDucks

Active Member
Ford Technician
Joined
May 25, 2020
Messages
337
Reaction score
63
Points
28
Location
B’ham AL
Vehicle Year
94
Make / Model
Ranger
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Did you read this entire thread and somehow come to the conclusion that you were the only person intelligent enough to know that?

That’s cute how you only quoted a small bit of my reply instead of all of it.
 

Rhinehart5

New Member
Joined
Nov 16, 2021
Messages
11
Reaction score
0
Points
1
Location
Arkansas
Vehicle Year
92
Make / Model
Ford ranger
Transmission
Manual
Ok. Here are the numbers.

18 gauge wire; resistance is 5.8 - 7.8 ohms per thousand feet. So, adding 5 ft of wire increases the circuit resistance by 0.029 - 0.039 ohms depending on temperature.

16 gauge wire; resistance is 3.7 - 4.9 ohms per thousand feet. So, adding 5 feet of wire would add 0.0185 - 0.0245 ohms depending on temperature.

I really doubt that the ecu circuits are sensitive enough to detect that. Your multimeter definitely is not. Make good clean solder joints and use heat shrink with sealant in it to keep moisture our.

If that feels like to much risk, just use the short harness and put the ecu in a waterproof box. It's all up to your comfort level and budget.

To put that in perspective, if a sensor circuit is running 30mA (0.03amps), then at about 0.035 ohms, your wire extension has dropped the voltage by 0.00105 volts.
Thank you! And one last thing if I decide to do a water proof box would I need to worry about venting it or anything like that? I’m not sure if the computer even gets warm or anything but I was wondering if it might cause it to over here when it’s air tight and no ventilation??
 

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
15,216
Reaction score
16,352
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.
I don't have a good answer for that. I don't think the factory location has any vent. But I've never looked at it closely. I believe Ford sealed it to keep water out. If you do your own box, mount it as far away from heat sources as possible. But the whole engine compartment gets hot in my opinion. There is something under the hood that has rapid-fire explosions happening inside it and heat is a byproduct.
 

Sponsored Ad


Sponsored Ad

Staff online

Today's birthdays

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top