Dale Gribble

Problem:
- Alarm goes off at random after locking car. Occasionally get one beep when car is locked. Doesn't matter if beep or not, alarm will go off at random.

- Alarm sounds like it's dying and gets weaker/more inconsistent as it goes off. Kinda like in the movies when a robot dies/gets electrocuted (think R2-D2 in Empire Strikes Back for fellow nerds out there).

- If the alarm stays on, the 15 amp fuse in the box under the driver's seat blows which kills the alarm, but unfortunately also the central locking as well as interior lighting.


Things that have been fiddled with on the car:
- Aftermarket radio
- Broken window on driver's side (the window doesn't roll down properly when you pull the handle)


Scanned with Durametric:
- UPDATED 4/4/13: A ****load of fault notices come up with error counts, but it says that these are here for information and do not indicate a fault or a repair is needed. Not sure what that means? It might mean that these were past issues. Screen shots of the durametric are below. Also is a screenshot of the various contacts that are showing opened/closed. Screen shot was taken after pressing the lock button while inside the car and then putting the key in the ignition to get the car to read the ECU so i'm assuming that's why a bunch of stuff is showing open when it should be closed or whatever.

Possible Solutions:
- I have no clue. Car is at a porsche shop so someone can go over it and try to find the problem.
- Do you think it's time to bite the bullet and replace the alarm brain? Car is a coupe so it's hard to imagine water having gotten in and shorting out the box.
- Radio or sensor is tripping the alarm at random, but that doesn't explain the fuse blowing on the brain or the alarm not working properly).

- UPDATED 4/4/13: Alarm brain was opened up. Nothing Shorted out. Mechanic went further up the wiring harness and found two exposed wires that could have been shorting out (contact with seat or other metal in the area?)

They have fixed that and since then have been unable to reproduce the issue that I have been having after having the car sit around for 2 days. Have not checked the radio yet but they will do that next.

Advice? Suggestions?

alpine003

First make sure the OEM security wire isn't touching the radio cage.

Did you diagnose or replace the switch on the driver's side? Could be faulty switch sending wrong signals to the alarm brain.

Dale Gribble

Shop is doing that now.
Mother of f***, we can't replicate the problem at the shop now. EVERY night the alarm would go off at my place, but after 4 days at the shop, it hasn't gone off. I think it's haunted...

alpine003

Is your place at an incline, either side to side or front to back by chance?

Dale Gribble

nope, garage is fairly flat. it goes off while it's in the garage too...
things we are going to look at are:
- radio
- window
- inspect contacts in decklid/frunk
- possible that the controlbox is damaged
- possible that when I move the seat, it's contacting/shifting the harness and shorting out the box.

The FOB in the remote is on low battery as well, but i don't see how that would cause any issues since the problem happens with the manual key as well. It's possible that the key head is damaged..not sure what that would do to the alarm's functionality.

jumper5836

I get a horn beep as well. The only thing I can think on mine is that it is from the aftermarket radio. But my alarm does not go off.

You have a motion sensor alarm? Maybe that has shorted some where. Fuse blowing makes me think it's a short somewhere.

Dale Gribble

All the 996's have a motion sensor inside the car from what i've read on here. Yep, urs is beeping once because of the radio. Mine does that too sometimes...not always.

jumper5836

You should fix the micro switch that triggers the window to open a crack. Need's to be fixed anyways.

function12

Have you tried double pressing the lock button to turn off the motion sensor to see if that is the problem? Try leaving the motion sensor off for a few days and see if it still goes off. If it doesn't leave you could have found the problem.
I would also check the battery voltage. Low voltage causes these cars to do goofy things. New radio may have to much stand by draw.

Dale Gribble

Updated the main post with new info and Durametric Screenshots

alpine003

Interesting on the exposed wires. Did someone tamper with it to make them exposed?

Dale Gribble

Could have happened if they got caught on something under the seat.
In any case, the alarm problems are gone, my car runs great and I am one with the universe again.

alpine003

Which wires were exposed exactly? Some under the seat? I'm wondering if this is something isolated or something that could happen to others too. Either way, glad you got it working again.

Dale Gribble

Mechanic says he's seen it happen before, but I suspect that it happened in my case because an aftermarket remotestarter/alarm was installed.

Things to note:
- Alarm now doesn't beep when locked....ever.
- Pressing the lock button on the fob beeps the car once like it should, indicating the motion sensors are disabled.
- if you lock the car with the key

LI911

Not to hijack here but I guess I found the right thread. Car's in the garage and my alarm went off at 4am this fine Saturday and now I can't back to sleep because I want to figure out the problem. It went off Thursday afternoon too, it's only been twice but I have to assume it's somehow related to the stereo I put in last Sunday.

Things to check:

1) Battery charge - my battery did die when I was playing with the new radio after install Sunday, I jumped it and took a 10 minute ride. I also took it for a 60-75 minute ride on Thursday afternoon. I did a bunch of short trips yesterday so maybe it's just the battery. I put the top up and down a few times on these sort trips too. Hoping this is the issue.

2) OEM security wire (I remember carefully reattaching to the horseshoe and sliding the boot back over it - but i'll double check it)

3) fuse under seat

4) harness - under seat?

Anything else?

Thanks as always for any advice.

I need to fix this problem quickly as random alarms in the night will not help my insomnia.