My security alarm / horn went off last night at about 4 am. The drivers side door wasn't even locked and the keys were not in the ignition.
The horn was sounding a short blast about once a second or so and the lights were flashing.
When I opened the drivers door, the horn quit sounding but the lights kept flashing. I tried inserting the key in the ignition but the light still kept flashing. Eventually I removed the battery cable and went back to bed.

Has anybody ever had this happen to them? How can I prevent this from happening again? What caused the alarm to trip in the first place?

 

Was it the factory alarm or do you have an aftermarket alarm installed as well? I installed a keyless entry several years ago that would interfere with the factory alarm and it would trip the factory alarm after a few hours of sitting.

 

I have had the same thing happen to me as well. Only when I opened the door the car kept honking the horn. It happened 3 times all after sitting in a parking garage for about 5 days. Other than that it doesn't work. I eventually had to pull the battery positive as well. Honestly the wiring in my car is hacked up, but I don't know what it could be. Never was enough of a problem for me to spend any time trying to fix, especially since it would be really hard to replicate it.

My alarmed tripped either because I stuck the key in the door or tried to open the door cant remember which. Also it may be worth mentioning that I only have the valet key for mine.

 

FYI if this is the factory alarm...

Inserting the key into the ignition does not disengage the factory alarm. Only turning the locks in the unlock position in the driver's, passenger's, or hatch door will disarm the alarm.

 

It is the factory security system.

I read a message that said it is possible to permanently disarm the security system on the S5. Does anybody know if I can disable thsi security system on my 88 S4?

The neighbors were probably not pleased. The car is parked in my driveway right now.

 

Actually, I believe that it's probably easier to disarm the factory alarm on S4's. The reason is because the alarm control unit is its own separate unit on S4. (S5's have it built into the CPU).

The unit is located on the passenger side behind the dash, I think. I'm going off of memory, and I've no S4. You should be able to just pull the plug to the unit.

 

As covered above, the key does not disarm the alarm when you put it into the ignition (and in fact triggers the alarm again when you do that).

The factory alarm disarms by turning the key to the unlock position in a door or trunk/hatch.

If the factory alarm is falsing, 50% of the time it is related to a bad trunk seal and it is raining, or that the latch switch (what you lock and unlock the doors with on the inside of the car) is dirty or out of alignment.

Unplugging or permanently disconnecting the alarm is not a solution. Fix the car instead of breaking it further.

 

i just permanently grounded my rear hatch latch and took the "hatch" bulb out of the idiot cluster to disarm the factory alarm.

 

I also had this same problem for years off and on. I took the door switch apart and cleaned and aligned the lock switch circuit board. No problems since, that was 3 years ago. It was very easy to fix I wish I had done it sooner.

 

this happend 2 me once and i got freakd out! i was holy ajshdahdsa!!! WTF is going!!! its a demon!!!!! then i just unlockd the door and it turned off, phew....i had 2 cancel the priest 2 come down. saved me like 100bucks!