"Alarm status indicator" LED on rearview mirror

[csieminski]

On my 1990 535i, there is a good-size red LED at the base of the rearview mirror, facing the outside of the vehicle. I have seen E39's with this light, and it flashes when these cars are parked.

Based on some research I have done, I believe this light is for the factory alarm. I was hoping it would flash when the car is locked or double-locked (it doesn't), and today I tried entering a code into the onboard computer and securing the car (still doesn't flash, although the red "code" LED on the OBC remains illuminated, as it's supposed to).

Does anyone know what I can do? I'd like the LED to flash anytime I lock or double-lock the car. My car was produced too early for keyless entry, and to my knowledge it doesn't have any alarm. But it does have that intriguing LED.

[jeffreyb4me]

Hello again 'csieminski' ! You come up with great questions. The LED lense in your mirror might actually be functional [have a harness coming out of the mirror] but is not connected to the car. I've never looked but pull the domelamp & sunroof drive cover down and peak at the top of the mirror to see. I think BMW had planned on offering DWA III on early E34's but didn't until the 540's came out and could be optioned with Key Remotes from the factory. The OBC 'CODE' function is not an alarm but an early type of 'driveaway' protection [quite easily defeated] and only 'connects' to the DME. If your car had a dealer installed alarm, there'd be a small red LED and glass breakage mic. at the rear of the console above the tunnel, between the seats with it's control unit under the L/S of the rear seat.
If that mirror's LED is function [not just a dummy lense] you certainly could wire it into an aftermarket or dealer available alarm system. I've never seen it done but you've got a great idea there.......................Best To You !!.............jeffb.

[csieminski]

Thanks, my "great questions" are the result of not having enough money to worry about legitimate (but expensive) upgrades to my car, so I see if I can inexpensively utilize the existing functions of my car (as in fixing the power headrests).

There's no LED between the front seats, so I assume that the mirror LED is either dummy or for a non-installed alarm, as you said. My car is also prewired for a BMW CD changer, but cheapskate previous owner did not apparently get either item when he paid over $43,000 for the car in 1990.

I'm considering getting an $89.95 Stellar keyless entry for my car from Bavauto. It worked great in my 528e, and I remember there was a third button that could be utilized for another random electronic function (dome light, parking lights, etc.). Maybe I could tie this light into the system. All I'd like is for the light to flash when the car is locked. Anyone who wants my car and knows what they're doing will be able to have it, despite any alarm. But with the flashing red light, ordinary people will think I have an alarm (plus it just looks cool), and that's all that matters anyway!

///Thanks!