Alarm goes off frequently in warm weather

[greenheckler]

2001 Boxster Base 5spd

Yesterday my alarm went off about 5 times 15 to 20 minutes apart. 65 degrees and sunny ( I am in Southern California). Fortunately, I parked it in front of my home so I was able to notice it and turn it off via the keyfob. It got to a point where I kept the doors unlocked. Earlier in the day, I took it for a 9 mile drive.

Any ideas on how to start troubleshooting?

Thanks

[Paul]

The best way is to read the alarm codes. Have you done any work on the radio recently?

[thom4782]

This could be several things. Perhaps, your infrared sensor is beginning to fail. Less likely one of the sensors that detects motion might be going. It's really hard to know.

If you have a Durametric cable, you should start by looking for any stored diagnostic codes for the alarm system. This will give you some insight into what part(s) of the system might be triggering the alarm.

If you don't have a diagnostic cable, see if your local dealer or an independent shop will simply read the codes for you at a nominal or no charge. They should be able to read these in less than 10 minutes. If you post the codes here, people can tell you what they mean.

In my recent case, my central locking system would only act up on sunny days after the car was parked in sunlight. It had six or seven codes that didn't pin down the problem, but the overarching code suggested that the door locks were acting differently. By luck, I was able to narrow it down to the passenger side locking mechanism.

Good luck

[greenheckler]

Thanks Thom and Paul

I didn't think about the infrared and motion sensors. Are those located on the windshield area by the convertible top latch?

Paul, I do have an aftermarket stereo. Could you elaborate on why that would cause this?

Thanks again.

[thom4782]

The motion sensors are located near the rear view mirror on either side where the top clips to the windshield frame. They are behind the shinny pieces that look a bit like cat eyes.

There is a central alarm wire that attaches to the stock radio. It senses whether someone is tampering with the radio and it can short out with aftermarket ones because it's not connected to anything. The fix is to put a piece of electrical tape over the exposed wire.

[Paul]

The alarm system has a wire that is hooked up to the mounting bracket for the factory radio. If this wire touches a ground the alarm system thinks the radio is being stolen and activates. If the installer merely unhooked this wire and didn't insulate it properly it can short to ground. BTDT.

[sb01box]

if you suspect the motion detector is the root cause, you can disable it by double pumping the lock button on the fob.