• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Electrical Box of Spaghetti

  • Thread starter Thread starter kraze1
  • Start date Start date Jun 13, 2020
K

kraze1

Member
Feb 16, 2010
6
1
13
Philadelphia, PA
Jun 13, 2020
#1
  • Jun 13, 2020
  • #1
Hello everyone. I bought a clean '89 LX 4cyl roller to do a 5.0 swap. The previous owner did a 5-lug conversion w/Cobra brakes and planned on doing a 5.0 swap, but gave up on her & gave me a bunch of v8 parts in plastic bins. I was able to install the fuel & brake lines. All of the wiring for the car was in one of the large bins...unlabeled. For the most part, through research and internet pics, I figured out the wiring under the hood. The dash wiring has me stuck! I looked at veryuseful.com's diagrams and they are helpful, but what would really be a lifesaver would be a complete wiring schematic with an exploded view that really shows where everything goes. Right now I have a huge wad of wires and brackets coming out from under the steering column & I have no idea what the proper routing of the harness is.

Additionally, while doing my research I was able to look up the white box under my dash and found that it is a "Speed Control Amplifier" and is tied into the cruise control system. I'm installing a 5-speed manual T5, so it will not have cruise control. Do I need to keep this box plugged in & run the wiring outside the car, or can I eliminate it altogether? If I do not connect the speed control amp or the connections behind the fender, will it affect anything else?

Thanks in advance for your help!

- E
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Jun 14, 2020
#2
  • Jun 14, 2020
  • #2
@kraze1

PM me your email address and I will send you a complete Ford Factory 89 Mustang electrical diagram set. The zip file is 2.5 MB and is too big to fit through Stangnet's email gateway.

The plug shapes on the diagrams match the plug shapes on the actual plug. The diagram is divided up by the layout of the car. The first diagram is for the very front of the car, and it works its way to the rear of the car page by page.

They are in a zip file format to reduce the size of the package. If you don't have Windows 7 or Windows 8, or later, you’ll need WinZip or other Windows archive tool to extract them from the zip file.. See www.majorgeeks.com - Download Freeware and Shareware Computer Utilities for a free download.

You will need the Adobe Acrobat viewer which is also a free download – www.adobe.com/products/acrobat/readstep2.html - Adobe Reader download - All versions
 
Last edited: Jun 14, 2020
Reactions: General karthief
K

kraze1

Member
Feb 16, 2010
6
1
13
Philadelphia, PA
Jun 14, 2020
#3
  • Jun 14, 2020
  • #3
jrichker said:
@kraze1

PM me your email address and I will send you a complete Ford Factory 89 Mustang electrical diagram set. The zip file is 2.5 MB and is too big to fit through Stangnet's email gateway.

The plug shapes on the diagrams match the plug shapes on the actual plug. The diagram is divided up by the layout of the car. The first diagram is for the very front of the car, and it works its way to the rear of the car page by page.

They are in a zip file format to reduce the size of the package. If you don't have Windows 7 or Windows 8, or later, you’ll need WinZip or other Windows archive tool to extract them from the zip file.. See www.majorgeeks.com - Download Freeware and Shareware Computer Utilities for a free download.

You will need the Adobe Acrobat viewer which is also a free download – www.adobe.com/products/acrobat/readstep2.html - Adobe Reader download - All versions
Click to expand...

@jrichker Thank you. This will certainly help a lot. I will send you my info right away.
 

Blown88GT

Founding Member
Nov 13, 1999
2,283
524
164
Palm Beach Gardens, FL
Jun 14, 2020
#4
  • Jun 14, 2020
  • #4
kraze1 said:
...

Additionally, while doing my research I was able to look up the white box under my dash and found that it is a "Speed Control Amplifier" and is tied into the cruise control system. I'm installing a 5-speed manual T5, so it will not have cruise control. Do I need to keep this box plugged in & run the wiring outside the car, or can I eliminate it altogether? If I do not connect the speed control amp or the connections behind the fender, will it affect anything else?
....
Click to expand...
You don't need to plug it in & you can eliminate almost all the wiring to it.
However, the factory ECU & the Speed Control use the VSS (Vehicle Speed Sensor) which is attached to the T5.
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
VSS needs to be connected to pin-3 & pin-6 on the ECU.

1988 Mustang Electrical & Vacuum Troubleshooting Guide (EVTM)

File is too large to upload. Here is link to it on my Google Drive. View: https://drive.google.com/open?id=1on5czXKmpETzxUggWTGtoUuVkJT2UUxN
www.stangnet.com
 
You must log in or register to reply here.

Similar threads

S
Electrical No dash lights
  • slojoexxx
  • Dec 11, 2025
  • 1994 - 1995 Specific Tech
Replies
0
Views
142
1994 - 1995 Specific Tech Dec 11, 2025
slojoexxx
S
B
Electrical Why does my fox body keep frying eecs
  • brandyn200
  • Jun 20, 2026
  • Fox 5.0 Mustang Tech
Replies
8
Views
226
Fox 5.0 Mustang Tech Jun 25, 2026
AeroCoupe
Fox Fuel Pump Issues After Replacement/Upgrade
  • Ryu
  • Jun 23, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
23
Views
542
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jul 5, 2026
Ryu
Electrical VSS question
  • Mcmahst
  • Nov 22, 2024
  • Fox 5.0 Mustang Tech
Replies
14
Views
452
Fox 5.0 Mustang Tech Nov 24, 2024
Mustang5L5
S
Fox '87 GT can't get to stay running
  • spilly
  • Mar 29, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
27
Views
767
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 20, 2026
spilly
S
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?