Price - Stock No 500

Check Your Kit




1. Mount components to the PCB from the PLAIN SIDE. 




We can text the functionality of the unit with the vehicle's battery.  The 0V wire connects to the negative terminal of the battery. The parking light wire connects to the positive terminal.  When these two connections are made, the buzzer will sound.  When we connect the Ignition wire to the positive terminal (along with the Parking Light Wire) the buzzer stops.  Every time the ignition wite is removed from the battery, the buzzer will sound.  In one sentance:

When the Parking Lights are ON, AND the ignition is OFF, The Buzzer is ON.  

The option exists to install the unit in the steering column or in the engine bay.  As the Headlight Guard will only sound when the ignition is off (ie. the motor is off) the volume of the buzzer should be able to be heard from the engine bay.

In either case we will be required to make three connections to complete installation:


Almost all cars are 0V to chassis.  This means that any metal part of the vehicle will be 0V.  You may find a wire that is connected to the chassis, this is a good location to connect the 0V wire.


If mounting in the engine bay, tests will need to be run to determine a wire which has 12 V present when the parking lights are illuminated.  A good place to locate this is around the relay which controlls the lights.

With the steering column installation, locate the light switch and test the wires eminating from it to determine the Parking Light wire.  (12 V present when the parking lights are illuminated).  You may find the dashboard dimming control has a suitable wire for this connection.

As a rule, the parking lights will rem ain on when the headlights are on.  This means that the Headlight Guard will sound if either the headlights or parkers are left on and the ignition is turned off.


In the case of an engine bay installation (petrol Engine), the ignition wire can be connected to the positive connection of the ignition coil.  In diesel engines, connection may be made to the fuel cutoff valve. 

When installing in the steering column, identify the ignition wire, eminating from the ignition switch. 

In any case tests should be run to determine a connection point that has 12 V present when the ignition is on and 0V when the ignition  is off.

Three wire taps are included for easy installation. 


Check for dry joints, joints not soldered at all, or solder bridging PCB tracks.

Check locations of all components.

Technology Notes


If you are not familiar with the workings of a transistor and ohms law, please take some time to read how transistors work and Ohms Law .

When the lights are left on, and the ignition is off the Connection to Parking Lights is 12V and the Connection to ignition is 0V.  This means that a small current will flow from the emitter to the base, this turns the transistor on and supplies current to the buzzer through the collector (Hear Sound).

When the lights are on and the ignition is on, the current through the emitter / collector of the transistor is blocked by the 12V present on the Connection to ignition.  The transistor is off and no current flows through the transistor to the buzzer (Hear no Sound).

When the lights are off, the Connection to parking lights is 0V so again no current flows from emitter to base - the transistor is off (no sound).  The state of the Connection to ignition is irrelevant.

Finally the two 1N4004 diode is included to eliminate any feedback from the Connection to parking light to the Connection to ignition and vice-verca.  If the diode was not included, it is possible the vehicle may continue to run with the ignition off and the lights on (not desirable).


 View the  BC557 Datasheet

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