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Converting a 1973 A/T Engine Harness to M/T


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I have been working on creating a comprehensive diagrams so I can rebuild all of my wiring and I could really use some help with the last couple of details. I started with the full color wiring diagram that is floating around the internet and came from Classic Z Cars, but these specific things aren't covered in it, so please don't tell me to look at the FSM or the wiring diagram.

 

Context: The previous owner sold me the car largely disassembled so I have had to chase all of the wires and connectors and figure out what they go to. In the process of doing that I discovered that my engine harness is for an automatic, but I have a manual car. There are also a couple of wires that were snipped.

 

The first thing I need to understand is what one of the cut wires is for. It's a thin black wire (approximately 14 or 16 AWG) and comes out of the main trunk of the harness near the Seatbelt Relay connector. I traced it to the top left pin in the green connector (15B on page BE-2 of the FSM), which corresponds to a wire that is missing on my dashboard harness. This makes me think these wires are dedicated to the automatic cars.

Screenshot 2023-02-15 at 5.02.23 PM.png

 

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The next thing I need to understand is how the manual harness is different from the automatic harness for this year. I already figured out how the throttle opener solenoid wires are different, but I could use help with understanding the wires that go to the 4-pin connector on the manual cars and how they are different from the ones in the 6-pin connector on automatics used for the seatbelt relay.

 

The 6-pin connector wires are BY, BY, BY, B, G, G (#17 on page BE-2 in the FSM) and the wires for the 4-pin connector are GB, BW, BW, BY (#18 on page BE-2 of the FSM). I am pretty sure the GB wire on the manual is for the throttle opener solenoid and connects to the speed switch on the speedometer. I assume the BY wire on the manual replaces the third BY on the automatic. I have no idea about the others. I would have assumed there was a green on in there but no.

Screenshot 2023-02-15 at 5.00.58 PM.png

 

Here is a drawing showing how the wires in my harness are routed from the green connector to the Seatbelt Relay:

Screenshot 2023-02-16 at 7.37.56 AM.png

 

Notice that I have two BY wires going to my neutral switch, not green, and they come out of the seatbelt switch, not the green connector. If I understand correctly, on the manual cars the green wires bypass the 4-pin connector and go straight to the neutral safety switch. By the way, I know that the wires for the inhibitor switch are wrong in that drawing. On automatic cars replaces the neutral safety switch.

 

I need to know what the 4-pin connector on the manual harness plugs into since there’s no seatbelt relay on manual cars. I am assuming the green connector's BY wire and GB wire (marked as missing in the drawing above) go to that 4-pin connector. If the BW wires merge somewhere into one wire I have no idea where that BW wire would come from.

Screenshot 2023-02-16 at 9.59.41 AM.png

 

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The last thing I need to figure out is what the BY wire on the blue connector goes to. It's the center pin on the bottom (#15-A on page BE-2 of the FSM). This is completely missing on my engine harness, but also on my dashboard harness, which leads me to believe it is specific to manual cars, just like the GB wire for the throttle opener.

Screenshot 2023-02-15 at 5.08.37 PM.png

 

I would really appreciate help ironing these details out. It's the final roadblock on getting my wiring diagram done so I can start rebuilding it. Let me know if are details I should add that would help.


 

 

Edited by matthewabate
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