Hazard switch delete/replacement solution

[MaddieCycle]

Perhaps this has been covered elsewhere, but the time came for me to fix this hazard switch debacle.  Lubricated it etc...., bottom line is that these 34 year old plastic bits sat under the windshield for too long and finally disintegrated, turn signals working intermittently, lost my brake lights, so I did a rewire workaround.  Note this is for my 1986 KC with the combined full red tail lights. This is probably different for those years that have the red tail/brake and yellow flasher lights.

The switch is a 3PDT, it has two states.  In one state (hazards off), it passes through 2 connections: one to the turn signal circuit, and another that links the brake light circuit.  In the hazard-on state, it cuts the turn signal and brake light connections, and connects the hazard flasher unit (there are 2 flasher units in this truck, one to operate the hazards, and one for regular turn signal use) to the front and rear turn signal lights on both sides.    The switch is connected via a 10-pin connector right behind the dash at the steering column, 9 of the pins are active and one is a dummy. 

 

In my truck, the colors of the wires in the harness from the switch to the connector were not the same as the colors coming out of the connector and into the truck, which are also the colors listed in the FSM diagrams.  So, I removed the switch, cut it off the harness, and used a continuity test to identify each of the wires in the harness:

 

1 - Green/Yellow

2 - Green

3- Green/White

4-Green/Black

5 - Green/Red

6 - Brown

7 - Red/Black

8 - Red/White

9 - Red/Green (look closely, the green stripe and the black stripe look very similar)

 

Then what you want to do is create the following setup on a quadruple pole, double throw switch (switch has two positions, both are "on").

 

"On" state 1 (Hazards off): Connect 1 to 2 and 8 to 9. In this state, 3,4,5,6, and 7 should ALL NOT be connected to anything.  The way to do this is to put a diode between each of 4,5,6, and 7 and a common connection which is then connected to one of the two switch terminals.  Then connect 3 to the other switch terminal.  If you don't use the diodes, it won't work as connections between 4,5,6, and 7 will allow back-flow of current in the "hazard off" position and screw everything up when you use your turn signal or brake lights.

 

"On" state 2 (Hazards on): Connect 3,4,5,6, and 7 all to each other.  1 should NOT be connected to 2, and 8 should NOT be connected to 9. 

 

I wound up buying a 2-pack of 4 pole-double throw (4PDT) switches on Amazon for $13, that way if one turned out to be junk, I'd have a backup.  You can also get 12v diodes super cheap on Amazon.

 

Drill a hole on the extreme lefthand side of the dash and install the toggle switch there, click the connector back together, and enjoy reliable operation of all of these functions.

 

While you are at it with the steering column shroud removed, do the 5 minute easy tilt-wheel fix by removing the reverse thread bolt using a 12mm wrench, take the locking arm off and move it by a few splines, then tighten.

Edited October 3, 2020 by MaddieCycle

[MaddieCycle]

Here is a circuit diagram. Also I forgot to mention above that you need to use diodes to keep 4,5,6, and 7 disconnected from eachother in the hazard off state, so I updated above.

[datzenmike]

Kind of complicated and the Nissan switch doesn't use diodes.

[MaddieCycle]

On 10/2/2020 at 8:35 PM, datzenmike said:

Kind of complicated and the Nissan switch doesn't use diodes.

I'll bet there are diodes inside that body that protrudes with "Niles" written on it.  Can't make this work without diodes.  I would have loved to have not done this but the switch is NLA new and ebay ones are pricey and also likely to be just as old and janky. YMMV, this worked for me.