Hazard Switch Wiring Diagram

SouthArk370Z

Ah. For some reason I was under the impression that your wiring was different than the '09 FSM I'm using. Apparently it's just the wire colors.

There does appear to be some miscommunication here. Not unusual on the Intertubes. I think the main problem is my mistaken belief that your wiring was different.

You only need one of the grounds (assuming the other end of both wires is a good ground, which it should be). I'd go ahead and connect both ground wires. If you only connect one, use the largest wire (but I'm guessing they are the same size).

It is "good engineering" to isolate computer circuits from "external" circuits but that's a bit of overkill in a modern car where you have excellent grounding. Plus, this is a digital I/O line, not an analog sensor, and noise is not as critical when you are looking for on/off. Theoretically, separate circuits would be best; in practice, it doesn't make a lot of difference. I'm guessing that the reason Nissan did it their way is: If the ground for 3-terminal switch has high resistance (eg, corroded connection), then it would be possible for the power going to the light to feed into the switch circuit (and vice versa) - as long as you have a good ground, that shouldn't be a problem. Even with a poor ground, it shouldn't be unsafe, to you or the car, in your situation. It might not work right, but it shouldn't do any harm.

As long as you have a good ground, the light should work properly. The "other" end of both wires are grounded and at the same potential, so, electrically, the terminal ends are the same.

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