Shopping: Real Estate |  Costumes  |  Guitars
This Issue Archived Articles Blog About Us Contact Us
SEARCH


Adding a Beep to Your Locking

An audible indication that your car is locked

by Julian Edgar

Click on pics to view larger images

At a glance...

  • Adding a 'door locked' indicator to your remote central locking
  • Very cheap - just one or two components used
  • Easy to do - no workshop manual needed
Email a friend     Print article
This article was first published in 2009.

Nearly all cars of the last 15 years have remote central locking as standard. You press the button on the key and the locks slam. Sometimes you’re notified of what has happened by a beep or flash of the indicators, but in other cars there’s no indication at all. The latter can be a bit of a pain – until you test a handle, you’re never quite sure that the car is locked.

Click for larger image

What this little project does is beep when the doors lock. There’s no indication when the doors are unlocked (none is usually needed), and the modification will work with all systems – including those like the one shown here that use a single button on the key to both lock and unlock the doors.

The Approach

The basic idea is to wire an electronic buzzer in parallel with the door lock solenoid or motor. These motors (or solenoids) are fed current with one polarity when unlocking the doors and the opposite polarity when locking the doors. If you put the buzzer the right way across the wiring, it will sound only when the doors are being unlocked.

The Parts

Click for larger image

To make the sound you’ll need a 12V electronic buzzer. This should be fairly loud as in use it will be buried inside the door, muffling it. You might also need a diode, but we’ll come back to that later.

Removing the Door Trim

Click for larger image

The first step in the install is to remove the door trim. We chose the driver’s door but any door with electric locking can be picked.

Click for larger image

Be careful when removing the trim. In addition to clips, there are often a few screws, usually hidden. In this car (a Toyota Prius), there was a screw hidden behind a flap inside the door handle...

Click for larger image

...and another inside the armrest. Remove these screws before gently prying the door trim loose.

Click for larger image

The inners of the door cavity are usually protected by a plastic liner, held in place with adhesive black mastic. Gently pull this loose, starting in the area where the door lock motor is likely to be.

Finding the Right Wires

Click for larger image

In the case of this car, the locking button is connected to the door lock mechanism by Bowden cables. By following these we were able to find the door lock motor itself.

Click for larger image

Here is the lock motor, almost completely hidden inside the door. But there’s no problem – we don’t want to access the motor itself, just the wires leading to it.

Click for larger image

And here are those wires. The bundle is wrapped in loom tape but...

Click for larger image

...this is easily sliced open to reveal a bunch of wires. But which ones are the right ones to connect the buzzer to?

Testing

Click for larger image

The answer is easier than you’d first think. Just carefully bare a small portion of each of the wires, making sure that they cannot touch each other or the metalwork of the car. Then try connecting the buzzer to the different wires until it sounds briefly when the doors are locked.

Yep, that easy.

If you are using an electronic buzzer, you won’t do any harm if you connect it across the wrong wires first.

Click for larger image

Once you have found the right wires for the buzzer, try unlocking and locking the car a few times. In some cases you might find that the mechanism is now a bit erratic. If this is the case, this little critter – a diode – is likely to be able to solve the problem. (Small diodes are available from any electronic store – a 1N4004 is fine.) Wire it into one wire going to the buzzer (try each way around until the buzzer still works) and then check that all is again fine.

Soldering

Click for larger image

Insulate the previously bared wires that aren’t required and then solder a pair of wires to the correct leads. Thoroughly insulate these connections with tape.

Click for larger image

In the case of the Prius, the diode was needed and it was connected up next.

Click for larger image

The new cable was wrapped in tape and then the system again tested.

Buzzer Mounting

Click for larger image

The buzzer was mounted inside the door using double-sided tape – out of view in this pic but that’s what the fingers are doing! Be careful when picking the mounting position to ensure the window can still move up and down without being obstructed.

Click for larger image

Again to avoid fouling the window mechanism, cable-tie the new wiring into place.

After that it’s just a case of reassembling the door trim and you’re finished. Now, no more wondering if you really did lock the car!

Did you enjoy this article?

Please consider supporting AutoSpeed with a small contribution. More Info...


Share this Article: 

More of our most popular articles.
A 2-amp variable voltage power supply for under $10!

DIY Tech Features - 1 October, 2013

Cheap Power!

The mechanics of diesel engine fuel systems

Technical Features - 20 January, 2007

Common Rail Diesel Engine Management, Part 1

30 cylinders, 21 litres and 470hp!

Technical Features - 25 July, 2008

The Chrysler A57 Multi-Bank Engine

Understanding virtual swing arms and virtual centres in suspension systems

Technical Features - 7 April, 2009

Virtual Suspension

Advancing the ignition timing can result in better fuel economy

DIY Tech Features - 28 April, 2008

The 5 Cent Modification

How to design for ultra light weight

DIY Tech Features - 15 June, 2007

Making Things, Part 7

The best shape for inlet pipes

DIY Tech Features - 29 January, 2002

Ballistic Bellmouths

The frame, seat and chain path

DIY Tech Features - 16 June, 2009

Chalky, Part 6

The story of the wonderful BMW M1 - a purpose-built racer

Special Features - 7 April, 2009

M1 Magnificence

You don't need an expensive factory towbar harness - even on CAN bus cars.

DIY Tech Features - 4 August, 2009

Towbar Electronics

Copyright © 1996-2020 Web Publications Pty Limited. All Rights ReservedRSS|Privacy policy|Advertise
Consulting Services: Magento Experts|Technologies : Magento Extensions|ReadytoShip