Jump to content
Mysta2

Ignition switch wiring ('79 620)

Recommended Posts

The socket that connects to the rear of the ignition switch in my truck has 4 wires (it's a 6 socket plug and the switch has 5 leads, but there are only 4 wires)

 

I'm not sure what they all are and I can't find a wiring diagram that matches much of what I see under the hood of the actual truck.

 

Confirmed are the following:

1. white (heavy gauge) - Battery positive.

2. Black w/yellow - Starter motor

3. Black w/white - Fuel pump

4. Blue - Unknown

 

#3 runs the fuel pump, but is this just switched power? Does it run everything?

What is #4 supposed to do? If #3 is just the fuel pump then #4 must be the rest of the switched power circuit. I don't get any spark at all to indicate a closing circuit when I touch the battery positive to it (white).

 

Thanks

Kit

Edited by Mysta2
  • Like 1

Share this post


Link to post

The #3 probably just powers the fuse box that the pump is wired too...just like the coil. 

  • Like 2

Share this post


Link to post

There are 3 wires from and to the '79 620 ignition switch.

 

White....  brings 12 volts to the ignition switch, hot at all times.

 

Black/Yellow.... start signal to the starter solenoid. Hot only in START position.

 

Black/White...  Sends power to the ignition relay in the engine compartment which powers the ignition module, fuel pump, powers half the fuses in the fuse box. Hot in ON and ACCY.

  • Like 3

Share this post


Link to post

- Hmm. That does seem to be how mine works... bonus wire for extra credit? -

 

Thinking about this a little more:

 

The switch needs to have 4 wires:

 

ACC= Lights, radio, gauge cluster?, fuel sender?

OFF= nothing

RUN= Lights, radio, gauge cluster, fuel sender, fuel pump, Coil

START= Lights, radio, gauge cluster, fuel sender, Coil, starter

 

So the ACC needs to be on it's own wire (the largest circuit with everything short of running the engine)

RUN wire (Black w/white) could just be the fuel pump and coil.

Start wire (black w/yellow) would have to be just the starter.

Hot wire would have to be there to power all of this.

 

...so the blue must be the ACC circuit.

 

I welcome any corrections to my conclusions.

 

So what is powered in these trucks with the switch turned to ACC? Does the fuel guage come on in the ACC position? Does the cluster light up? My wiring is a mess and I can't be sure anything is connected to the blue wire at the moment. As already noted, it doesn't spark at all so it seems that it may not be connected to anything.

Edited by Mysta2
  • Like 1

Share this post


Link to post

I looked at the diagram and blue goes to the radio. I assume switch 12v power

  • Like 2

Share this post


Link to post
On 4/24/2019 at 10:06 PM, Mysta2 said:

- Hmm. That does seem to be how mine works... bonus wire for extra credit? -

 

Thinking about this a little more:

 

The switch needs to have 4 wires:

 

ACC= Lights, radio, gauge cluster?, fuel sender?

OFF= nothing

RUN= Lights, radio, gauge cluster, fuel sender, fuel pump, Coil

START= Lights, radio, gauge cluster, fuel sender, Coil, starter

 

So the ACC needs to be on it's own wire (the largest circuit with everything short of running the engine)

RUN wire (Black w/white) could just be the fuel pump and coil.

Start wire (black w/yellow) would have to be just the starter.

Hot wire would have to be there to power all of this.

 

...so the blue must be the ACC circuit.

 

I welcome any corrections to my conclusions.

 

So what is powered in these trucks with the switch turned to ACC? Does the fuel guage come on in the ACC position? Does the cluster light up? My wiring is a mess and I can't be sure anything is connected to the blue wire at the moment. As already noted, it doesn't spark at all so it seems that it may not be connected to anything.

 

All exterior lights including brakes and dash (but not signals) horn, clock, interior light do not need the ignition switch. They are available at all times.

  • Like 2

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.