I live in a neighborhood that some people are scared of, and I drive an old car that is very easy to break into and steal. I didn't want to put an actual car alarm in my car because of the cost and their proclivity for false alarms. So, I decided to make a fake alarm for my car with a flashing red LED while installing my car stereo.
Warning: Do not attempt this instructable without assistance if you have no knowledge of wiring. Doing so can result in serious damage to you and your vehicle. You will also need to drill at least one hole somewhere in you dash. If you don't feel that you can do this without damaging the internal workings, then don't try this. If you have a newer car with anti-theft features I also advise you not to try this as screwing with the wiring of your car may trigger them and render your car or it's stereo useless.
Step 1: Supplies
Here's what you'll need to pull this off:
1. Linrose B5100H1FL Panel Mount Flashing LED, Red, 20mA, 12v $3.50
Can be obtained via Fry's Electronics:
(Any flashing LED that works on 12 volt DC power will do.)
2. Wire tool for stripping and crimping connections. Approx. $3 to $5
These can often be obtained with the connectors
3. Red wire crimp connectors
4. Access to hot and ground wires that are not controlled by your ignition switch
5. Extra wire
5. 12 volt toggle switch (optional)
7. A drill and drill bits
You really should already have these. If not I advise you to seek assistance before attempting this instructable.
Step 2: Wiring
1. First off, for safety, disconnect the ground (black cable) from your battery. Be advised that you will lose your presets on your radio, but that's going to happen in the next step anyway and at least you're less likely to be shocked.
2. Decide on the place you want to put your LED and toggle switch, it you chose to use a toggle switch. Be sure you can access the the other side of the dash where the hole is to be drilled and that you'll be able to get wires from "point A" (your stereo) to "Point B" (your LED and/or your toggle switch). You also want to make sure your LED is visible to potential thieves, and that your toggle switch is hidden. Another very important thing to check is that you will not be damaging anything important when drilling the hole for these items. Once you're sure of all of this determine what size your holes need to be, then drill them.
3. On your car stereo locate the yellow wire and the black wire. The yellow wire is the hot wire that provides power to your car stereo while the ignition is off. You will need to cut and splice this wire and run one side to one of the wire to your LED. Basically you cut yellow wire strip each side. Then you crimp a red connector on one side of the wire. On the other wire you twist together a piece of *extra wire long enough to reach your LED then crimp them to the other side of the connector.
*If you want to be able to turn your LED off, be sure to leave enough wire to reach the place you've chosen to mount your toggle switch.
4. Repeat the previous step, this time splicing the black wire. This time you only need enough wire to reach the LED, unless you decide that this is wire you want attached to the switch, it doesn't matter which you choose.
5. Now, if you're not using a toggle switch you simply strip then connect the wires to the LED.
6. If you're using a toggle switch you will need to run one of your wires to the switch attach it to the switch, then add another wire to the opposite side and run that wire to your LED then attach it. If +/- is noted on your LED, connect the yellow wire to the + positive (red wire) wire on the LED, and the black wire to the - negative side (black wire) of the LED.
7. Now you just need to mount the LED and Switch. Then put everything else back together.
8. Once you've reassembled everything you are ready to reconnect the ground wire to your car battery. If you've done this without a toggle switch your LED will begin flashing. If you have a toggle switch check to make sure it enables/disables your LED. If all is well then you're done. Congratulations!
Step 3: Mission Accomplished!
Now that you're done you can now enjoy many of the benefits of a car alarm without any of the annoying false alarms. Don't worry about the drain on your battery, your flashing LED would take years of no driving to run down a healthy car battery.