Hazard Switch – Brake Light – Turn Signal Circuit Analysis

Boy, did I bite off a lot with this one. However, these three circuits all come together at the Hazard Switch, so I chose to take on the challenge and analyze them all at once. I used the 72 FSM as my guide. I am including a PDF of this analysis as well.

Since this is a labor of love that takes significant time to put together, I ask that you give me and my blog full attribution if you choose to post my work elsewhere.

This guide will work for the 1972 Datsun 240Z.
It should work for a late 1971 240Z.
It may work for a 1970 or early 1971 240Z.
It should work for a 1973 240Z except that the physical layout of the Hazard Switch is different as are some of the connections between the Dash Harness and Engine Harness and between the Dash Harness and the Body Harness.
I hope this helps with any work you are doing with these circuits.

(Update: Image revised on 2015-03-07 to correct errors and change to color.)
Hazard Turn Brake Circuit v2-1

From the positive post on the battery, the cable runs down to the starter.
At that point it connects to the Fusible Link.
The Fusible Link connects to a White wire.
The White wire connects to the Dash Harness, and then to SPLIT 1.

SPLIT 1 (Power Source for Hazard Lights and Brake Lights)
One branch of the White wire continues to the Fuse Box.
It goes to the fuse and comes out Green/Yellow.
The Green/Yellow wire goes to SPLIT 2.

SPLIT 2 (Hazard Lights Branch)
One branch of the Green/Yellow wire becomes Blue/Yellow and goes to the Hazard Flasher.
A Green/White comes out of the Hazard Flasher and continues to the Hazard Switch.
When the hazard lights are activated, the Green/White wire makes contact with the following wires:
White/Black
White/Red
Green/Black
Green/Red

SPLIT 2 (Brake Lights Branch)
The other branch of the Green/Yellow wire goes down to the Brake Pedal Switch.
When the brake pedal is depressed, the Green/Yellow wire makes contact with another Green/Yellow wire.
The Green/Yellow wire travels to the Hazard Switch.
When the Hazard Switch is off, the Green Yellow wire makes contact with another Green/Yellow wire.
The Green/Yellow wire then goes to the steering column and on to the Turn Signal Switch.
When the turn Signal Switch is in the middle position, the Green/Yellow wire makes contact with both the White/Black wire and the White/Red wire.
When the Turn Signal Switch is in the right turn position, the Green/Yellow wire only makes contact with the White/Red wire.
When the Turn Signal Switch is in the left turn position, the Green/Yellow wire only makes contact with the White/Black wire.

SPLIT 1 (Power Source for Turn Signals)
The other branch of the White wire goes to the Ammeter, and comes out White/Red.
The White/Red wire goes to the Ignition Switch.
When the Ignition Switch is in the RUN position, the White/Red wire makes contact with Black/White wire.
The Black/White wire goes up to the fuse box, goes through the fuse, and comes out Green.
The Green wire goes to the Hazard Switch.
When the Hazard Switch is off, the Green wire makes contact with another Green wire and goes down to the Turn Signal Flasher.
The wire comes out of the Turn Signal Flasher as White.
The White wire goes to the steering column and changes color to Green.
The Green wire goes up to the Turn Signal Switch.
When the Turn Signal Switch is in the right turn position, the Green wire makes contact with the following wires:
White/Black
Green/Black
Green/Red
When the Turn Signal Switch is in the left turn position, the Green wire makes contact with the following wires:
White/Red
Green/Black
Green/Red

Coming out of the Hazard Switch and Turn Signal Switch…
The Green/Black wires join and go up to the Right Front Turn Signal.
The Green/Red wires join and go up to the Left Front Turn Signal.
Both front turn signals go to a Black wire that is grounded with the Negative post of the Battery in the engine compartment.
The White/Black wires join and change color to Green/Black before going to the Body Harness.
The Green/Black wire at the Body Harness goes back to the Right Rear Turn Signals.
The White/Red wires join and change color to Green/Red before going to the Body Harness.
The Green/Red wire at the Body Harness goes back to the Left Rear Turn Signals.
Both rear turn signals go to a Black wire that is grounded to the chassis in the rear of the car.

(Update: Image and PDF revised on 2015-03-07 to correct errors and change to color.)
Circuit Diagram

PDF of this post.

Advertisements
This entry was posted in 240Z, Electrical, Tech Tips. Bookmark the permalink.

30 Responses to Hazard Switch – Brake Light – Turn Signal Circuit Analysis

  1. Pingback: Hazard Lights - Brake Lights - Turn Signal Circuit Analysis

  2. Pingback: help identifying some wiring - ZCAR.COM - Datsun : 240Z, 260Z, 280Z, 280ZX, 300ZX, 350Z, 370Z : Nissan

  3. Pingback: Dashboard Instruments Out & Blow Signal Fuse - ZCAR.COM - Datsun : 240Z, 260Z, 280Z, 280ZX, 300ZX, 350Z, 370Z : Nissan

  4. Pingback: Headlights

  5. Pingback: Help needed: Alternator not charging and Turn signals not working.

  6. Pingback: A Question Regarding Turn Signals and Hazards

  7. Pingback: mystery blinker problem

  8. Pingback: Help! Electrical issue: 1973 240z, turn signals work, hazards do not

  9. Pingback: Voltage at driver brake light drops to 0 when load applied

  10. Pingback: 72 z rear turn signa problem - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

  11. Pingback: Turn signal flasher-71

  12. Pingback: Need some turn signal help

  13. Pingback: One brake light working

  14. Pingback: Turn Signals and Brake lights cease to function.

  15. Pingback: all sorts of eletrical gremlins(260z)

  16. Alex says:

    Great write up. Looks like the 260z shares a lot of that information.

    • Thank you. I did use the circuit break-outs in the 74 FSM as an inspiration for this post. I think this diagram is easier for the novice to follow that having all of the wiring diagram together.

  17. Pingback: Intermittant Brake Light Problem

  18. Pingback: Right front turn light (amber) not working

  19. Pingback: Adding a relay to turn signal and brake light circuits? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

  20. Pingback: 71 240z taillight fix - ZDriver.com

  21. Pingback: Front right turn signal light

  22. Pingback: 1972 Datsun 240z - ZDriver.com

  23. Pingback: 240z Electrical and Carb Issues - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

  24. Pingback: Brake lights always on?

  25. Pingback: 1972 240z Hazard switch removal? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

  26. andrew says:

    help me!!! I am in the process of rewiring my 1973 240z father son project. we are using the ez wiring harness. question i have is; rear taillights
    , you have 4 prong connector. RB back up lights, B ground, GW taillights, GB or GR turn signal and brake light. How can you run the brake light and turn signal on the same wire?

    • First, take a look at where I took apart a 240Z turn signal switch. https://fiddlingwithzcars.wordpress.com/2012/12/04/turn-signal-repair/
      You can see there are two switches inside the turn signal switch. One connects the brake light circuit to the rear lights, and the other connects the turn signals to the rear lights. When you move the lever, you break contact to the brake lights on that side. That’s how one wire can be connected to two circuits.
      If that’s not a good enough explanation, let me know, and I can probably email you with more details.

  27. Luis says:

    Hello I have a 1972 240 z and I have a problem whit the left side stop lights i did check if is any power on the wires and i have a low light on my power tester device which means there is power but not enough for the light bold, light bold new also signal and parking lights work perfect but not the stop light on the left only right side works perfect, any idea what could be the problem?

  28. It is likely the turn signal switch. Here is a guide I wrote on cleaning it: https://fiddlingwithzcars.wordpress.com/2012/12/04/turn-signal-repair/.
    If you don’t wish to tackle it, I can refer you to someone whom you can pay to clean it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s