• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

12V Circuit Up based on Hazard flashers

Not open for further replies.


New Member
I hope this isn't too elementary for this group, but I have need for very simple a 12V automotive circuit that will light a lamp continuously based on the vehicles' hazard flashers being on. (Background: the tail lights on an equipment trailer are hidden when the gate is open. Have added some LED strobes that can be seen by oncoming traffic, but they need a continuous 12V power source. I would like for them power up whenever the (intermittent power) to the "hazards" is active.) Any suggestions? Thanks!


Well-Known Member
Most Helpful Member
I'm 95% sure that the hazard lights use a flasher separate from the turn signal flasher, so the power being switched by the hazard push switch is just steady dc. Intercepting the wire between the switch and the flasher module would do it.

A wiring diagram for the towing vehicle would answer that. Have you Googled for the wiring diagram?

A 555 Timer chip wired as a re-triggerable one-shot with a period longer than the time between flashes, followed by a dc relay would do it, too.
Last edited:


New Member
I have the wiring diagram for the 1993 through 1997 Altima and it's typical of what I remember. It uses one flasher module. I've never seen a car (except pre-1970 retrofits) with two different flasher modules, but that doesn't mean they don't exist, it means I haven't seen one.

Some cars may still have a place you can get 12 switched from the hazard switch. These 93-97 Altimas do not.

You would need a diagram of your car to be sure, or as MikeMI suggested as an alternative, use a retriggerable one shot.

If your LEDs don't consume much power, you could run them from the blinkers. Charge a 470 uF 25V capacitor thru a diode from each blinker and power the LED from the capacitor. If it almost works, try a larger capacitor.


New Member
Good suggestions, both!

Thanks for the replies.

I should have pointed out that this needs to be self-contained within the trailer, so intercepting the hazard circuit before the flasher would work, but would require an non-standard additional wire to the trailer (which needs to be standard so it will function the same way no matter the tow vehicle).

The strobes currently get their power from the "tail lights" through a manual switch. I can intercept the intermittent power from the "hazards" when they are on so it would be nice to either: 1) actually provide the power to the strobes, or 2), keep a relay closed so I can power them from the continuous "tail light" source.

This would help prevent the idiot driver (me) from forgetting to turn off the strobes while tooling down the street.

The diode/capacitor might just do the trick, but would I have to be concerned that it might continue to power them for some time after the flashers were turned off - or is that just a function of proper sizing?

adartse ral

New Member
flasher relay circuit and hazard circuit for automobiles

i am a student want to know the flasher relay circuit and hazard circuit for automobiles thanks and more power

Not open for further replies.

Latest threads

EE World Online Articles