Well I bought my e28 a few weeks ago and rummaging around I saw 2 remotes in the glovebox. I tore the car apart trying to find the keyless entry unit. Unlike my e34, it wasn't under the rear seat. I finally managed to find it tucked in the roof of the glovebox. To my surprise, I was somehow able to actually get it working, in sync with the siren in the engine bay and all. The alarm is an oem BMW unit, but upon looking through service records and reciepts, it seemed the po had it installed about 4-5 years after he purchased the car new.

I have one problem though, when pressing the button for the doors to lock, they will all go correctly down and the alarm will set, but they will only stay down for about 1 second and all come back up again. Any ideas?

Btw, the central locking works correctly if I use the key to lock the doors.

Here's a picture of the unit I have in my car:

http://i14.photobucket.com/albums/a314/ripcurl530/DSCF3073.jpg

Congratulations dude, you've got a very rare system there; one that I've never seen there before. I don't know anything about the system but if the central works fine from all doors without it than I'd be looking at the output to the central L- module and the input to the keyless Module. Unfortunatley I think its the keyless module.

I have had a similar problem on my '88 528e and found that if my trunk lock key cylinder is left in the "unlocked" state (horizontal) my doors will do the same thing when I lock the car with either the key or the keyless fob. When I turn the key in the trunk so that the trunk does not unlock when the doors are unlocked, the doors remain locked.
My best guess is that the problem is in a switch or the actuator for the trunk. When I found the work around I didn't pursue it any further because I don't mind unlocking the trunk to open it.

Hope your circumstances are as easy to live with.

I have had a similar problem on my '88 528e and found that if my trunk lock key cylinder is left in the "unlocked" state (horizontal) my doors will do the same thing when I lock the car with either the key or the keyless fob. When I turn the key in the trunk so that the trunk does not unlock when the doors are unlocked, the doors remain locked.
My best guess is that the problem is in a switch or the actuator for the trunk. When I found the work around I didn't pursue it any further because I don't mind unlocking the trunk to open it.

Hope your circumstances are as easy to live with.

Well now that you mention is my trunk lock is extremely sticky, it takes several times to get open and when it opens you have to push it several times before it finally pops open.