Make A 90-93 5.0 Engine Harness Work With A 89 Dash Harness

mark32

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Hi, is there a way to make a mustang 5.0 1990-93 engine harness a3m computer work with a 89 dash harness? Please let me know if there's anyway to make this work other than buying a whole 89 engine harness, thanks!
 
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imp

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Hi, is there a way to make a mustang 5.0 1990-93 engine harness a3m computer work with a 89 dash harness? Please let me know if there's anyway to make this work other than buying a whole 89 engine harness, thanks!
Sure, you can make any harness work anywhere you want, if you are able to rip it apart, check and trace each and every connection against wiring schematics, make the needed changes, as harnesses as well as color codes changed a lot during those years.

I will be surprised, but not too much, if someone can give you a clear "yes" or "no" here. Sorry. imp
 

imp

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I know its been answered but im willing to tear apart the 93 engine harness to make it work with the 89 dash harness if its possible. Thanks for the answers.
To answer that, we need to know which functions of the EFI are handled by the dash harness. As I recall, my 89 had the PCM Power Relay and PCM itself both mounted behind the RH kick panel. Seems like there was wiring under the driver's seat, Fuel Pump Relay comes to mid. That would be fed-through from the dash harness. Only other thing I can think of in the dash is the CEL, fed by the PCM. There were no other PCM connected functions, I don't think. I don't have '89 wiring diagrams, but DO have 1990; will take a look at them. I had a '93 Cobra, but forget, but think, the PCM Power Relay by then was in the Battery Junction Box, underhood.
 

mark32

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To answer that, we need to know which functions of the EFI are handled by the dash harness. As I recall, my 89 had the PCM Power Relay and PCM itself both mounted behind the RH kick panel. Seems like there was wiring under the driver's seat, Fuel Pump Relay comes to mid. That would be fed-through from the dash harness. Only other thing I can think of in the dash is the CEL, fed by the PCM. There were no other PCM connected functions, I don't think. I don't have '89 wiring diagrams, but DO have 1990; will take a look at them. I had a '93 Cobra, but forget, but think, the PCM Power Relay by then was in the Battery Junction Box, underhood.

Hi, thanks for the reply and the information. Diagrams of all these harnesses would be the best but I myself cannot find them.
 

imp

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Hi, thanks for the reply and the information. Diagrams of all these harnesses would be the best but I myself cannot find them.
Schematic diagrams are good electrically, but they do not show connector locations within the vehicle. Most good wiring diagrams DO show the relative shapes of connectors, which does help some. imp
 

nelzfoxes

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I thought engine harness is stand-alone? Ford’s aftermarket swap harness is based off of the 93 harness. That harness m-12071-a50 is what I used to convert the Daddywagon. Ford used to sell the 93 harness itself as a swap harness I believe. I think your answer is yes. Shouldn’t be too hard. Maybe 1 connector of wires different between years. And as mentioned earlier move 1 or 2 relays. The dash or chassis wires don’t share much with the engine harness I think. VSS, A/C, Tach, KO power, ground, engine light, power in start & run? I wanna say connector by wiper motor but not positive.
 

mark32

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I thought engine harness is stand-alone? Ford’s aftermarket swap harness is based off of the 93 harness. That harness m-12071-a50 is what I used to convert the Daddywagon. Ford used to sell the 93 harness itself as a swap harness I believe. I think your answer is yes. Shouldn’t be too hard. Maybe 1 connector of wires different between years. And as mentioned earlier move 1 or 2 relays. The dash or chassis wires don’t share much with the engine harness I think. VSS, A/C, Tach, KO power, ground, engine light, power in start & run? I wanna say connector by wiper motor but not positive.

Thats great news! Does anyone have the two pin out diagrams for both 89 dash harness and 93 engine harness diagram. Also any other info and pointers before i rip apart the 93 harness.
 

jrichker

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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.

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
 
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nelzfoxes

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I am not sure what you mean by “rip apart the harness”. Is the 89 a 5.0? You shouldn’t have to rip it apart.
 

mark32

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I am not sure what you mean by “rip apart the harness”. Is the 89 a 5.0? You shouldn’t have to rip it apart.
Hey, no the 4cyl 89 is the dash harness and I'm converting it to 5.0 using 93 stuff. I'm keeping the 89 dash and going to cut up/modify whatever on the 93 5.0 engine harness to make it work with the 89 dash Harness since you said the 93 can be run stand alone.
 

imp

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I am not sure what you mean by “rip apart the harness”. Is the 89 a 5.0? You shouldn’t have to rip it apart.[/QUOTE]
You "rip it apart" only to the extent that if connections as indicated in schematic diagrams do not match pin numbers on connectors, you must remedy that, so that all sensors and such are properly connected.

Working year-to-year has shown me that early in the '90s Ford began skipping wiring conductor colors around, as well as maybe conductor numbers. This means that an EFI harness off an '89 may have different connections than a later one. IN GENERAL, '89 to '93 are pretty alike, but no guarantees. '94 up definitely different.

If yer installing an EFI motor in an early car, for example, you had better have wiring diagrams relating EXACTLY to the EFI harness used, or exact wiring information relating to the engine, year, and model being hooked up. Horrible headaches can happen otherwise. (Been there). imp
 

rd

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Ran into this way back trying to use an 80 engine harness and the 80 dash harness with 82 gages. Did not want to use the 82 engine harness because it was for a straight six and had two many wirenut connections from the previous owner.

Smoked the alt gage.

So, I checked the pinouts at the dash on both harnesses, I think I had both wiring diagrams. It turned out the 82 dash harness would plug into the 80 engine harness and run the 82 dash perfectly.

Suggest check that both engine harness have the same pin config at the dash harness connector, then check the pinout for the dash connection.
 
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