Simple Tweak Alerts You When You’ve Left Your Headlights On


[Paul McGuinness] owns a Series III Land Rover, and as the vehicle as formerly used by the British military, it’s lacking some of the modern amenities he was accustomed to. Overlooking the lack of power steering and all-around drum brakes, the one item that [Paul] really missed was a buzzer that let him know when he left the lights running.

On more than one occasion, he’s had to have “The Sarge” jump started after leaving the lights running all day. Explaining the humiliation involved with jump-starting a Land Rover with a Nissan Micra (an unfortunate excuse for a vehicle, known here in the states as the Nissan Versa) in his blog, [Paul] decided that he’d had enough – it was time to build a headlight warning buzzer.

The circuit itself is straightforward, consisting of a normally closed relay connected to his headlights and ignition, along with a buzzer. When the key is in the ignition and the lights are on, the relay is open and the buzzer is silent. However, if the lights are on and the relay is not supplied power from the ignition, it closes and sounds the alarm.

A simple fix for a frustrating problem – we like that.

47 thoughts on “Simple Tweak Alerts You When You’ve Left Your Headlights On

  1. Why not just wire the headlights to shut off when you turn the car off? I find any kind of headlight chime extremely annoying, because it shouldn’t be something I have to deal with. What if I actually do want the headlights on when the car is off for once, you ask? It could be set up so that if I turn them off then back on, they will go on, or I could just turn the key to Accessory. I can’t imagine any situation when I would want to leave the headlights on but wouldn’t want to leave the key in the car.

    1. What if you get home and the power on the street is out and you want to illuminate your front door and some of your house while you get inside? I mean, you could separate your house keys from your car keys and then go at it, but that seems a bit much.

      Or, what if you’re somewhere you want more light, like packing up after dark at a crowded park or beach after a party and you want the extra light from your headlights but don’t want to leave your keys in your car, or even leave your car unlocked?

      I mean, those are just two possible situations off the top of my head, but I’m sure that people who don’t live in luxury could find more situations where extra light without the risk of leaving keys in the car is a reasonable desire.

      1. I think many cars these days have a timer that will keep the lights on for a certain amount of time, then shut them off. I’m guessing a cool trick is to have that control (potentiometer) to control the length, so if you need it for longer you can set it up, but it will always turn itself off (eventually) if the keys are not in start position.

      2. I keep my car keys from my house keys seperate anyways.

        Since I often go out of the house without needing my car but very rarely find myself out of the house with my car without my car keys ;)

        thus less pocket cluster.

    2. You’re right, that would be taking this hack to the next level. In response to “No One’s” counterpoint, maybe you could use a manual override [just a button/switch that disables your circuitry] in the odd event you want the lights to stay on.

    3. Another solution would be to implement something that a lot of newer cars have: a timer for the headlights. That way you can leave them on if you want, but eventually they will go off so you don’t drain the battery. Though I don’t like cars that *always* leave the lights on after you turn the car off. Normally I just want the lights to be off.

    4. there are many situations where you need to leave the lights on with the keys out. Landrover thefts are up alot, so keeping you keys on you whilst you work by headlight is benefical to you insurance.

      Plus landrovers are old, the wiring on them are designed by people who, back in the day, would have thought it was obviuos that you turned your lights off, cos you could see that they were on!

      I’m sticking this hack on my landy right now!

    5. *Some* Toyotas have a great feature: you can leave the lights turned on always. When you turn off the car, they remain on until you open the driver’s side door, at which point a relay shuts them off until you turn the ignition on again.

      If I were modding his car, that’s the way I’d set it up. Hondas of the same vintage do not do this, and not all Toyotas do. Mine’s a 1998 Camry and it does.

      1. My 89 Corolla GT-S had this auto-off feature too and so does my 2010 Prius. It’s pretty awesome.

        It only works when the car is first turned off and then you open the driver’s door. To get the headlights on again.

        When you get back into the car and turn it back on, the lights come right back on.

        If the lights get shutoff and you need them on again (while the car is turned off) you just turn the control stalk to off and back on again.

        Very simple and elegant solution.

  2. On an old landy you don’t even need that level of complexity.

    A small buzzer with a diode in line mounted between the headlights and the ignition will do. The buzzer passes insufficient current to keep the ignition coil live.

    On newer cars this may not work so well if the ignition signal is used to drive a relay that the high current devices hang off – the buzzer might even pass enough current to keep the car running!
    (been there, seems that the midget alternator warning lamp passes enough current to keep a modern k-series engine running)

  3. I wish I had thought of this when I had my old ’64 Chevy.

    As far as the times you need to leave your lights on to rummage in the garage or whatever, leave them on. He didn’t disable the lights. I’d just close the door so I didn’t have to hear the thing. I doubt it would bother me. It’s not like he has it honking the horn or something.

    Pretty cool hack, IMO.

  4. Great idea!
    It seems mine no longer works and have had to get a jump a few times because of it.
    Btw the Nissan Micra is a great car !(yes I own one)
    And I don’t think it is the same as a Versa, both look very different.

  5. I did something similar for my 1975 Lancia Fulvia. I bought a beeping reverse light, removed the lamp from it and then wired it between the headlights positive rail and the driver side courtesy light door switch. This means that the beeper goes off any time the lights are on and the driver door is open, but it’s a pretty uncommon condition, and works well as a warning. The diodes were taken off failed fluorescent light bulbs, rated at 1A each, and I wired several in parallel to ensure they would withstand enough current to the courtesy light portion of the circuit. I think it’s unlikely that the lights would draw much more than a couple of amperes, though. Hackish, but it has not failed so far.

  6. Why don’t you just use the hand crank to start the engine when the battery dies? That what I always did on my ’73 Series III in the same situation (open palm technique, of course). I really missed that option when I started driving my wife’s old Honda and left the lights on one time (the buzzer had stopped working many years earlier).

    1. I have done in the past, but when the battery is *completely* flat, there isn’t enough to charge the coil and get it firing… Tried it the day I had to get the jump start off the Micra :shamed face:

  7. That’s weird, my old Audi didn’t have a headlight buzzer, but it had these two huge warning lights on the front of the car that light up when the headlights were on. If you got out of the car, and the two huge warning lights were lit up, that meant you forgot to turn off the headlights. When you turned off the headlights, the two huge idiot gauges on the front went dark. I’ve often by labeled the “absent minded professor” by my associates, but even I could figure out if the two huge warning lights positioned at the front of the car were on, that I had forgotten to turn off my headlights.

    1. You are assuming that a) It’s fully dark outside, b) I’m going to walk to the front of the Landy (which I don’t where I park it), and c) That the headlamps cast more light that a half-burnt candle…. :oP

  8. Gotta love the oldies built to last. Mine is an antique tagged 81 f150 ranger straight six with borg-warner t18 4 speed. No abs, fuel injection, high-lamp, air bag or any modern safety other than 3500lbs of steel, Vacuum power steering and front discs. Gas mileage is around 10/city, but my insurance is only 250/yr and new parts are often in stock locally, dirt cheap and easy to wrench.

  9. Here’s how I do my vehicles – I got the idea from a Popular Mechanics article from the ’60s, no less:

    I connect the + lead of the buzzer to something which is hot when the lights are on – a dash light is good.

    The – lead of the buzzer goes to the wire attached to the oil pressure switch – the one that lights the OIL idiot light on the dash.

    This works because the pressure switch is closed if the engine is off – no oil pressure, switch closes and the oil pressure light goes on – and so does the buzzer, if the headlights or park lights are on. When the engine starts and oil pressure builds up, the lead floats, the buzzer will not sound.

    Added benefit: if you lose your oil pressure you are warned by a buzzer, as long as your lights are on.

    I once did this to a Mustang that had an oil pressure sender instead of an idiot light. I installed a tee where the pressure sender was, and added a pressure switch for the headlight alarm.

    1. Ah… You assume that the Oil pressure light comes on in my 30 year old Landy (and that it has any working dashboard lights!) – Seriously though, it is a good idea, but these things are so basic you wouldn’t believe it. The whole vehicle has 4 fuses, and the headlights use 5 relays (take a look at the light switch in my blog and you’ll see why)

  10. Obviously don’t know cars that well. Versa in the states is a Tiida in the reast of the world. The Micra is a whole level of car below the Tiida. So low it isn’t even offered in the states. Also the Versa sold in the states is the hot rod, unless you get the base model you get the bigger 1.8 engine. Not sure how it all worked out with the new Versa just released, but that is how the original Versa was.

  11. Ah. I could use that in my ’93 Mitsu Pajero, can’t really belive Mitsubishi didn’t think about that 20 years ago… Or it’s just one more thing that has stopped working in that bloody vehicle.
    Will probably wire something like that to it soon, jump wiring a 2,2 tonne 4×4 from a Ford Transit didn’t feel that good…

  12. First off, who the hell wrote this article?

    That “poor excuses of a car” has a buzzer built in standard.

    It also by miles more reliable then that English piece of crap. ADAC/TüV proves this, which is really well respected institution on automotive tests.

    Not even to speak about fuel consumption, seeing all the green hacks, I’m very disappointed by this insulting tone.

    Better engineered also, using a chain instead of a rubber belt for engine distribution.

    So please tell me, since when are personal opinions valued more then facts here on HAD?

    That “car”is just a vintage piece of automotive engineering that should’ve been sent to the scrapheap a long time ago.

    1. Hmmm. Let’s see – If you compare the carbon footprint of my 30-year-old Landy that has done 40,000 miles, and compare it to your car with all its computers, rare-earth chemicals etc. I wonder which comes up on top?

      Instead of ‘throwing away’ the vehicle simply because it is old, I use it as a workhorse for taking my 3 Irish setters to the beach, collecting logs for my burner and taking rubbish to the recycling plant (instead of letting the local authority land-fill it!)

      And… The Nissan Micra (the old one that jump started me) is a poor excuse for a car. It’s the size of a cornflake packet, and I wouldn’t want to be in one in an accident LOL :o)

  13. I have a ’96 Chevy Blazer and on more than one occasion, I’ve come out to a dead battery because the damn rear hatch was either left open by me or accidentally popped open by the Keyless Entry. In this modern age, It’s just pathetic really that GM would design a vehicle that will allow itself to suck it’s own battery to death. Even more pathetic that there isn’t an after market product that will send a signal to an alarm into your house to let you know that your vehicle is in the driveway killing it’s own fool self.

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