Adding a Headlights Warning Buzzer to my Series III Land Rover

Dear Avid Reader,

Despite the superb performance of my Landy in the snow, the poor beast fell foul of that terrible affliction… human error.

It seems that I simply cannot remember to turn off the headlights when getting out of it on a cloudy day (or at dawn/dusk).

In order to save the embarrassment of having the guys at the office try to bump-start it (with a completely flat battery), or the ignominy of being jump-started by a Nissan Micra (yes… it happened), I developed a simple circuit using an old relay and a cheap buzzer in order to stop this happening again.

If you want to check wiring colours for your Land Rover, look at my Manuals page [here]

As you can see, the Relay being in a ‘Normally Closed’ position would make the buzzer sound all the time the lights are on, but the power from the ignition opens the relay and stops the buzzer sounding. When you turn off the ignition and remove the key, the relay closes, and if the lights are still on, the buzzer sounds.

This isn’t complicated, but boy does it save some hassle.

Now… the next thing to do is build this into as small a package as possible, and determine the least intrusive way of connecting the 3 wires to the Land Rover without having to dismantle the dashboard!

After procuring a simple NC relay (courtesy of the local Motor Factors), I planned the connections out as follows:-

I then soldered some wires onto the buzzer, and crimped connectors onto all the cables as you can see. The reason for using a ‘NC’ (Normally Closed) relay, is that when then ignition is in the ‘on’ position, the relay is charged, and the contacts open. Therefore breaking the connection and stopping the buzzer from sounding. When you turn off the ignition, the buzzer will sound if there is power to the bottom leg of the relay (labeled ‘Lights+’ above). Therefore If the lights are off, no power = no buzzer, and if the ignition is on, open-contacts = no buzzer.

Next, I needed to connect it to the wiring in my Landy (which as you can see, is a bit archaic!) – On my ex-Military model, the Blue/Black wire is live when the main headlamps are on (I didn’t want the buzzer for side-lights, just in case I wanted to park it on a lane and leave those on). The earth was snagged from a screw into the bulkhead (where most of the relays seem to be earthed anyway!), and the Ignition live was derived from a spare spade connector on the Ignition barrel. You can probably find your particular wiring diagram [here]

Job’s a good ‘un – Buzzer sounds now if I leave the headlamps on with the ignition off.