Headlights off with key.

[Ben A...]

Hey,
My car is 73 Duster.
I keep leaving my headlights on with the engine off when I park the car.
Can I modify the light switch so it only has power with key on position?

Would that mean just switching the tan wire to a key-on accessory fuse?

Would this affect other electronics in the car? Anything I'm not considering?

Thank you,
Ben

 

[Dana67Dart]

Best thing to do would be to wire a relay inline with the feed to the headlight switch. I think there are 2 cir that feed the headlight switch one for headlights and one for parking lights (only about 50% sure about that, I'm getting old)

In which case a double poll single through relay would do both

The relay is triggered by the run cir.

Whenever key is in run, headlights COULD be on

 

[Ben A...]

Best thing to do would be to wire a relay inline with the feed to the headlight switch. I think there are 2 cir that feed the headlight switch one for headlights and one for parking lights (only about 50% sure about that, I'm getting old)

In which case a double poll single through relay would do both

The relay is triggered by the run cir.

Whenever key is in run, headlights COULD be on

That's a much better approach than what I had in mind. Safer, easier. Thank you sir!!

 

[67Dart273]

PLEASE DO NOT DO THIS!!! One reason headlights are wired "hot" is for SAFETY!!! There is way more chance that the ignition switch circuit will FAIL and that is the last thing you want, tootin' down the road at 1xxxxxxxxxxxx mph!!!

Build yourself a headlight warning alarm, VERY VERY easy to do. You pick up the wire coming out of the light switch going to the dimmer switch, put a series diode and your choice of a loud annunciator/ alarm/ buzzer in there, and connect the other end to switched ignition switch power.

Diagram I shamelessly stole online LOL

 

[67Dart273]

HOW IT WORKS. When the ignition is on/ lights off, the diode prevents any power conduction, and it does not sound
With key on and light on, there is 12V on both sides of the device, no conduction, no alarm
But with key off and lights on, power flows through the circuit, and the loads on the accessory circuit form a ground return to activate the alarm

 

[Ben A...]

PLEASE DO NOT DO THIS!!! One reason headlights are wired "hot" is for SAFETY!!! There is way more chance that the ignition switch circuit will FAIL and that is the last thing you want, tootin' down the road at 1xxxxxxxxxxxx mph!!!
View attachment 1715938355

Hmm... a buzzer! I suppose my interest in safety is greater than my hatred of buzzers.
Interesting, thank you. Very straight forward wiring.

Out of curiosity... What are the safety considerations for the headlights to be wired hot?
I suppose if I wired headlights to power only with key on, and the ign circuit were to fail while driving (is that common?), I could be flying down the highway with no lights or engine power? Ooof.

Is there some clever way I could wire it to power the headlights only with key-on, but provide some sort of failsafe power circuit if the ignition switch circuit fails? Or would that get so complicated it's not worth the effort?

Thank you for your help

 

[67Dart273]

Again, safety. You could device some sort of "latching" circuit (relay) but those can fail too. You don't HAVE to use a buzzer, as I said "the annunciator of your choice" There are lots of them nowadays. I bet if you look around you could even find a voice module, some "hottie" voice "hea---head-lights sweetie" LOL

 

[Ben A...]

Again, safety. You could device some sort of "latching" circuit (relay) but those can fail too. You don't HAVE to use a buzzer, as I said "the annunciator of your choice" There are lots of them nowadays. I bet if you look around you could even find a voice module, some "hottie" voice "hea---head-lights sweetie" LOL

Hahah, fantastic idea. Perhaps I should wire this voice module for a few things... Even the kickdown "ooo! faster!"

 

[Dana67Dart]

PLEASE DO NOT DO THIS!!! One reason headlights are wired "hot" is for SAFETY!!! There is way more chance that the ignition switch circuit will FAIL and that is the last thing you want, tootin' down the road at 1xxxxxxxxxxxx mph

And if your new car has a headlight relay failure or if crackedback's headlight mod fails, or if the headlight switch fails...
My 96 Jeep GC has automatic lights with a photo sensor and a computer.

No difference.

I agree a buzzer will also work but OP asked about turning off the lights when the key was turned off.


IMHO your concern is unwarranted.

 

[crackedback]

And if your new car has a headlight relay failure or if crackedback's headlight mod fails, or if the headlight switch fails...
My 96 Jeep GC has automatic lights with a photo sensor and a computer.

No difference.

I agree a buzzer will also work but OP asked about turning off the lights when the key was turned off.


IMHO your concern is unwarranted.

Why you drag my name into this?

Also, my system has redundancy that an OEM wiring doesn't. Even if the low beam fails in my kit from any number of potential issues, you always have the other side to flip over to that has a dedicated power circuit.

You can't account for all potential issues. Every system will have a potential failure point. You can only set it up to minimize those points.

And yes you can wire in a relay to the main feed of the headlight switch. Just know the issues with doing so and install an override switch in case of relay failure.

 

[Dana67Dart]

Why you drag my name into this

Didn't mean any harm, it's just relays are used to run everything, planes,elevators and my point was there are other kits and OEM systems that can have a failure so the concern of using a relay to control your headlights was a moot point.

Your system is a good system and your redundancy is awesome. And I doubt anyone realized it had the redundancy you pointed out.

Sorry for dragging you into it.