FJ40 1974 Trailer Socket and Switch Electrical Question? (1 Viewer)

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How do you hook up the switch to the socket and the switch and socket to the harness?

I don't understand the Terminal Connections explained on the bottom?

The Trailer Socket has 7 connections
The Trailer Switch has 6 wires.
I also have 8 wires in the Socket/switch area.

My trailer switch does not have the male, female, and ring ends (They were changed). So I don't have a reference point like in the diagram.

Diagram taken from an old Thread discussing Trailer socket and switch (ended 2016)
Trailer Socket Change over Switch
Trailer Socket Switch 2.png



My Trailer Socket Switch Back Side View
ON is on the top
OFF is on the bottom

Left are 3 GY wires
Right are 3 GO wires

Trailer Socket Switch Back Side.jpeg


My Trailer Socket

Trailer Socket Numbers Back Side.jpeg
 
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Diagram doesn't show how to wire the trailer plug but the switch is straight forward. The purpose of the switch is so the flasher doesn't have an extra lamp load in the circuit. The switch is just a common double pole double throw switch. When you switch to the trailer the turn signals on the back of the vehicle will not work. If have a unused pin on the trailer socket would be easy to use a relay to do the same thing automatically.
 
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Isn't the Switch needed to control the rear turn signals etc.?
I think what I mean is you would need to run the wires straight to the rear combination lights if you want to by pass the switch and trailer.
The switch allows the electricity to go to the rear combination lights?

My initial plan was to set up in its stock configuration and then modify if needed.
 
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My understanding of the trailer switch diagram

1. GO - Turn signal switch TL terminal?
- Left terminal ? What terminals? From the Harness?
2. GY - Turn signal switch TR terminal?
- Right terminal ? What terminals? From the harness?
3. GO - To Trailer socket (left side turn signal light)
- What number on the socket would that be? Or does it even matter?
4. GY - To Trailer socket (right side turn signal light)
- What number on the socket would that be? Or does it even matter?
5. GO - Rear Left Turn signal.
- GB to switch
6. GY - Rear Right Turn Signal
- GY to switch

I just realize the GO and GY in color coding for the switch has nothing to do with the GO and GY in the harness.
It is to separate the 2 circuits?

If I understand the Haynes Trailer Switch Diagram correctly and matching it to the Trailer Switch Diagram from the factory manual (post#1)
1. GY from Harness
2. GB from Harness
3. GY to Trailer Socket
4. GL (GB) to Trailer Socket (GL should be GB color?)
5. GO (GB) to Left Signal Light (GO should be GB color?)
6. GR (GY) to Right Signal Light (GR should be GY color?)

X = is were I had cuts or after market crimps in harness wires

FJ40 1974 Rear Harness Diagram.jpeg
 
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Mar 16, 2015
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Okay I think I understand it?
GY and GB refer to the wires going to or away from the switch.
GY and GO from the diagram are not used in my explanation below.

1. GY (left turn) from harness
2. GB (right turn) from harness
3. GY (left turn) to Trailer Socket
4. GY (right turn) to Trailer socket
5. GB (right turn) to combination light
6. GY (left turn) to combination light

This means when the switch is ON these work?
1. GY (left turn) from harness
2. GB (right turn) from harness
3. GY (left turn) to Trailer Socket
4. GY (right turn) to Trailer socket
5. OFF
6. OFF

And when the switch is OFF these work?
1. GY (left turn) from harness
2. GB (right turn) from harness
3. OFF
4. OFF
5. GB (right turn) to combination light
6. GY (left turn) to combination light

Trailer Socket Switch 2.png
 
Last edited:
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Mar 16, 2015
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My next question would be what gets hooked up to the trailer socket?

My understanding of the SOCKET according to the Haynes Manual

1. Ground
2. RL (Why would it have reverse?)
3. G = Park lights
4. GW = Brake Lights
5. GL (GB) = Right Turn Signal
6. GY = Right Turn Signal
7. Extra?

Does it matter which number on the trailer socket things are hooked up to?

1 = Ground
5, 6 = come from the trailer switch.
2,3,4 = come from the harness.
 
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I found this in the thread I attached above. It gives the connections for a 1977 FJ40.

1977 FJ40 Trailer Socket and Switch connections.png
 

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