Installing an Alarm
on Your BMW
Wayne R. Dempsey

Difficulty Level: 4
Difficulty scale: Adding air to your tires is level one
Rebuilding a BMW Motor is level ten

[click to enlarge]

     Nothing is worse than having your BMW stolen or messed with. Although many BMWs came from the factory with a keyless alarm system, many did not. The good news is you can easily install either a factory alarm unit or an aftermarket one in your car in a short amount of time. BMW designed the car to accept an alarm and pre-wired all the connections for the alarm to communicate with the rest of the car’s systems. Installation is a snap—basically, plug in the unit and it will integrate automatically with the ignition cutoff, the doors, the trunk, and the windows. Good aftermarket alarm units, such as those manufactured by Stellar, are an excellent choice in place of the factory unit. The Stellar units start at about $250 and add a host of additional features like a microwave proximity sensor, integrated window control, shock sensitivity, and/or remote starting. The unit I chose for my 325ic convertible was the basic unit with window control and a microwave sensor. The microwave sensor is very important for convertibles, as it sounds the alarm if anyone goes near the interior of your car with top down.

     The installation procedure is very easy. Simply remove the glove box from your car (see Photo 2). Then locate the factory alarm plug (see Photo 3). Plug in the unit and route it along the side of the electronics compartment. At this point, you can plug in all of the components and test to see if the system is working. If everything tests okay, pop out the center onboard computer (OBC), the unit that displays the time, date, etc. It simply pops out if you place a credit card in between the seam on the upper part of the unit. With the OBC out of the way, you can pull up on the lower console piece that contains the cigarette lighter. It should also pop right out. Drill a small hole for the alarm LED indicator, and mount the microwave sensor underneath as well.

     The microwave sensor will have at least two sensor adjustments on the unit that you may need to play with for quite a while to get the sensitivity just right. The ideal location for the microwave sensor is in the center of the car, as long as it’s not obstructed by metal. Microwaves will go through fabric, plastic, wood, and glass, but they won’t travel through metal. Start the adjustment process by putting the top and windows down. Start walking toward the car. If the alarm goes off before you get to the car, then you need to reduce the sensitivity. It will take many tries before you get the settings just right so that if someone waves their hand inside your convertible, the alarm will activate. The microwave sensor can also be used on nonconvertible cars, but since they are locked most of the time, they are usually not necessary.

     Route all the wires for the LED and the microwave sensor down the side of the center console and into the glove box. Use some nylon zip ties to constrain the wires to the frame of the car. Drill a small hole in the bottom of the kick panel, and install the valet button; you need to be able to press this button while turning the ignition on in the car.

     Installation of the siren is also very easy. If you’re not using a factory siren, then simply tap into the two existing siren wires with some electrical wiretaps. Mount the siren in the engine bay, toward the front right side of the car (see Photo 5).

Synchronizing remotes with an existing factory system

     More often than you might think, BMWs will be sold without the factory remotes that control the alarm system. Since the BMW factory alarm doesn’t arm itself automatically, you don’t need one of the remotes to use the car on a daily basis. Many times a car is sold and the new owner doesn’t even know that there’s a factory alarm system installed. If you pop open your glove box and discover a factory unit plugged into the wire harness, that’s excellent news—all you need now is a remote control and some time to reprogram it. Remote controls can be found for about $100 or so at the dealer, or you can typically pick up a used remote for much less at swap meets or Internet auction sites.

     On the E36 models (and many other BMW models), the factory installed two different alarm types. The early type is designated by the three-button rectangular remote and was installed in cars up to August 1995. Starting in September of that year, BMW began installing an updated system distinguished by a two-button, round remote control. Both of these systems can be programmed to be used with new or replacement remote controls. The three-button remote reprogramming involves swapping chips into your factory control unit; see Photo 6 for the exact procedure.

     The two-button remote can be reprogrammed without having to take apart the glove box. Simply perform the following procedure:

Prepare the car

1. Close all the doors, the trunk, and front hood.

2. The alarm must be placed into disarm mode (not armed and not activated). If this reprogramming procedure doesn’t work after attempting it a few times, you may have to pull out the glove box and disconnect the harness to the alarm unit (or pull the fuse) to reset it and put it into disarm mode.

3. Remove the key from the ignition.

Start code-learning mode

4. Open the rear trunk, and leave it raised and open.

5. Open the driver’s door and sit down in the driver’s seat.

6. While sitting in the driver’s seat, close the driver’s door.

7. Turn the ignition switch on, then off, five times. Do not start the engine. Simply turn the switch to the on position each time so all the dash warning lamps illuminate. Important: All five cycles of the ignition switch must be performed within 10 seconds.

     The entire sequence of steps (one through seven) must be performed within 45 seconds. When the steps are performed properly, the red alarm LED will illuminate continuously, and the alarm siren will sound a single chirp. This indicates that the code-learning mode has been started. Do not start the engine at this time.

Register remote ID codes

8. While remaining in the driver’s seat, open the driver’s door.

9. Close the driver’s door.

10. Press and release any button on the remote control unit you wish to register with the alarm unit. The alarm LED indicator will turn off momentarily to indicate that the ID code has been registered with the system.

11. For additional remotes (up to a total of four), repeat steps 8 through 10.

Exit the code-learning mode

12. Open the driver’s door, and get out of the car, but leave the door open.

13. Close the rear trunk.

14. Close the driver’s door. The alarm status LED will turn off, and the siren will sound a chirp twice.

15. The registration process should be complete and you should be able to use all the remotes that you registered with the system.

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This photo shows the BMW factory alarm siren installed in the front right corner of the engine compartment (blue arrow). The yellow arrow shows the wire harness—if using an aftermarket alarm system, you may have to tap into this harness. The red arrow shows the factory siren mounting bracket.

Shown here is the BMW factory keyless alarm unit installed on cars up through August 1995. This controller works with the three-button remote shown in the left inset photo. The alarm controller is programmed to work with a specific remote by synchronizing the small chip in the remote to the alarm unit. Open up the alarm remote, and carefully remove the small chip (red arrow, lower right inset). Then pull out the alarm unit from your car, leaving the main wire harness attached. Insert the chip from the remote into the connector in the unit (blue arrow). Then turn on the ignition, and press the reset button for at least 10 seconds (green arrow). The red alarm indicator on your center console should flash, indicating that the codes have been read and accepted. Turn off the ignition, reinstall the chip in your remote, and test it—it should work! The later-style two-button remote used from September 1995 (upper right inset) uses a different synchronization method described in the main text.