1997 BMW 528i Q&A

1997 BMW 528i Question: Alarm System

The alarm system seems to go off for no reason often. What could the problem be and how can one overcome it? -
Answer 1
If it is a factory alarm, then the dealer is the one with the special coding tools, which are necessary. If it is an after market alarm and it is over 2 years old, the best thing to do is to replace it or remove it.They are not worth trying to repair and it is usually the module that is acting up which is usually not available after 1-2 years. -
Answer 2
I WOULD CHECK THE CARS BATTERY IF YOU HAVE A FAULTY BATTERY IT DROP VOLTAGE AND THE ALARM THINKS SOMEONE IS OPENING THE DOOR OR TRUNK ETC.SINCE THE ARLARM WORKS BY VOLTAGE DROP SO BEFORE REPLACING ANYTHING TEST OR HAVE THE BATTERY TESTED. -
Answer 3
Alarm is activated by sensors all over the car. The two that fail the most are the hood sensor and the audio sensor in the car. The cars computer keeps a record of which sensor trips the alarm. The cheapest thing to do is to disconnect the hood sensor. It won't affect the alarm, it just won't be in the system to trigger a fault. Or you could pay the dealer or someone else who has a computer fault reader. -
Comment 1
Is the "hood sensor" you are referring to called an "alarm system switch"? If disconnecting it is indeed the solution to the factory alarm randomly going off, shouldn't I replace it for about $16.00 and maintain the system as it should be? In other words, why is this switch in the system if it isn't necessary and "won't affect the alarm"? -
Comment 2
Thanks, I disconnected the plug to the alarm system switch under the engine hood and the alarm no longer randomly activates. When you say it "...won't affect the alarm, it just won't be in the system...", do you mean all of the other "...sensors all over the car..." still work and only the hood sensor no longer does? If this is the case, I ask as the previous post did, if I should replace the sensor for approximately $16.00 enabling the alarm to activate if the hood is raised while the system is in the alarmed mode? -
Comment 3
replacing the sensor may or may not fix your problem. If the plastic that supports the switch is cracked, forget it, there's your problem, it's creating enough movement for it to false trigger. Do you really need a hood switch in the alarm system. If they're opening your hood and you want the alarm to go off....they've already entered your car. -
Comment 4
Where is the switch located under the hood? -
Answer 4
The hood alarm switch plunger extension is made of plastic and snap off. My mechanic removed the switch and taped the plunger down in the off position. To reset the alarm, he inserted my key into the driver side door, turned the key to the right in the lock position and held it there for 30 seconds, then unlocked the key to the left twice. After that, no problems. Re. 1997, BMW, 528i, alarm problem. -
Comment 1
Why remove the switch, tape in the off position and reset? As far as I know, disengaging this sensor whichever way you choose does not require the system to be reset. I simply unplugged the sensor without having to reset anything. Disconnecting it simply means the alarm will not activate if the hood is raised. Don't get me wrong, I really appreciate your post. Please explain why the system has to be reset. Perhaps after he taped the switch the problem still existed and was only solved after he "reset" it? And hopefully he didn't charge you more than $16.00 which is the cost to replace the switch. -
Comment 2
where is the trunk sensor on a 97 528i located at -