Headlights on Reminder

By Roger Kizer

Saturday night at Carlisle this past year, a few of us went to dinner at a local restaurant. We drove our Barracudas to the eatery where we parked, went inside and were seated. It was a few minutes later when the waiter approached the table and said, "Which one of you own the white car? You left your lights on." Doh!
I think it's something we have all done at one time or another in our classic car. We have gotten used to the bells, buzzers or whistles we get when we leave the keys in the ignition or leave the lights on in our daily drivers. Who could blame us really? We're conditioned for the noise to remind us.
Well since nobody wants to come back from dinner to a dead battery, I present this article to give you that audio prompt to remind you to turn off your lights.

You will need a single pole double throw relay (SPDT) also known as a Bosch relay. A connector for the relay, a 12V buzzer or chime, an inline fuse holder and some wire and connectors. Here is the wiring diagram. Click on the image for a bigger view.
If your not up on your relays this is the diagram on how they work. pole 86 is grounded and when power is put to pole 85 it activates an electromagnet pulling the internal switch from 87A to 87. When the relay is un powered, a connection is made from pole 30 to 87A. When energized the connection is switched to create a connection from pole 30 to pole 87. This is how the chime will work. When the lights and the ignition are off, nothing is energized, no power through the relay. If you leave the key off, but turn on the lights, you will send power through the relay between poles 30 and 87A to activate the chime. If you turn on the ignition, the relay is energized at pole 85, pulling the internal switch and breaking the connection between poles 30 and 87A, stopping the current to flow through the relay to the chime.
You are probably asking yourself "Hey, what happens to the current going to pole 87"? We don't need to output any current to anything so we simply do not use that wire in our connector. Here you see pole 86(ground) is orange, pole 85(Ignition on) is red, pole 30(lights on) is white and pole 87A(output to chime) is black. The connector you have may be different, just refer to the diagram for correct wiring. Notice there is no pole 87 wire. That's because we do not need it in this application.
For your Ignition on power to pole 85, I would tap the fuse box. The heater fuse is powered only when the ignition is turned on.
When you remove the protective cover on the back you can see that there are some power taps ready to use. Just crimp or solder a female spade connector to your wire and connect it to the heater fuse.
Now since you are pulling ignition on power before the fuse, you will need to add in an inline fuse connector to protect the circuit. You can use the style shown or one for a glass fuse. A 3A fuse should do the trick.
For the lights on power to the 30 pole on the relay I tapped the radio connector for power. I'm using the power here to power the light in my tach, adding a wire here for the relay is easy. No fuse needed here as the power is fused before it gets to this point.
You can buy a buzzer or chime from your local auto parts store or electronics supply house. Just ground the chime and connect the power lead to the 87A pole on the relay. You can also use the chime from any car. That option my even have a more pleasant tone than the store bought buzzer.
Here is what it looks like all wired up. I used a plastic wire tie to mount the buzzer to the fuse holder. The red wire from the fuse holder will go to the power tap in the fuse box while the white/black wire will go to the radio connector to get lights on power.
Heres another view. I did solder the wires here and used shrink wrap.
I mounted the relay/fuse/chime harness by drilling a hole in the Brake pedal bracket. I used some electrial tape to keep the wires together. I used the mounting screw for the relay as the ground for the buzzer and relay. The buzzer works great and is not too loud, a perfect reminder. If you are having problems with the dimmer portion of your headlight switch, the buzzer might not work. I had this issue and resolved it by replacing the switch. I hope this little project will leave you with a fully charged battery after you stop for dinner during cruise night.