BMW Repair: keyless entry, 318is, middle button


Question
Hello, just bought a 1994 318is. It has keyless entry. There are three buttons. The top one is to lock/unlock the doors. The bottom one is the panic button. Could you tell me what the middle one does? When I push it, I hear a click under the hood but nothing seems the happen. Thank you.
By the way, what does the is stand for after the 318?


Answer
Casper,
 The 2nd button is usually to activate the alarm.  So if you press the first button it will lock the doors, but if someone pulls on the handle, the door will remain locked and nothing will happen.  If you hit the middle button it will activate the alarm, and if the handle is pulled it will set off the alarm.  This is on most BMWs, so your's might vary slightly.

 The numbers on the back of the BMW tell you what series the BMW is, and what size engine.

 318 = 3-series 1.8 Liter engine (4 cylinder)
 325 = 3-series 2.5 Liter engine (6 cylinder)
 525 = 5-series 2.5 Liter engine (6 cylinder)
 528 = 5-series 2.8 Liter engine (6 cylinder)

 The "is" on the back usually denotes that the car is a coupe (2-door).  A 328i is a Sedan (4-door) and a 328is is a Coupé (2-door).  That's the difference between the cars.  Most people think the "s" means sport, but you can have a 318is and it not have the sport package.
 Hope this helps,
 Josh