anewbill

Please help. All of a sudden my alarm has started going off for no apparent reason. The car will just start honking away after 5-20 minutes of being locked. I have checked all of the door switches including the glove box, trunk and engine lid. I also checked the battery voltage per Adrian's book just in case that could be causing the problem.

The battery voltage is 12.5 when I first shut the ingition off, then it drops to 12.34 after around 15 minutes (about the same time the alarm starts to go off).
At idle the voltage is 13.69 and it rises to 13.72 at 1900 RPM.

I also tried leaving the glove box open to see if that would prevent the alarm from sounding. This did not help. The LEDs just flashed twice per second to indicate an alarm fault and then the alarm went off after about 10 minutes.

Any and all ideas are very much apreciated!

Andy

dfinnegan

I had a similar problem. I would lock the doors and the alarm would sometimes go off ten or twenty minutes later; sometimes a couple of hours later.

I then began having trouble with my door locks. I would lock the car, turn to walk away, and the door locks would pop back up.

It turned out to be a limit switch problem. The lock motors in the doors can be moved up or down to adjust the switch setting. After adjusting the passenger door lock motor (Hammer got me there) I no longer have locking problems. Nor do I have alarm problems.

If you can gain access to a Bosch Hammer that will help in diagnosing where the problem is coming from.

Cheers,
Dave

darth

Same problem here, I disabled each switch one at a time so that there was no possible way they could trigger the alarm then when the alarm triggered I disabled the next switch and so on. After disabling every switch it turned out to be the infamous green radio wire.

Hope this helps
Bill
90C2

anewbill

Thanks for the advice guys!
Bill,
How do you disable the switches? I assume you are talking about the door, hood, and glovebox switches that turn the lights on and off?

Thanks,
Andy

agentpennypacker

I just pulled the fuse : )

anewbill

Ok, so I just did some more troubleshooting over lunch. I tested the door, hood, engine cover, and glovebox switches by holding them in and then arming the alarm. All of the switches correctly activate the alarm when released.

I did notice that the small metal flap the covers the key hole on my drivers side door appears to be stuck open. This is causing the key to stick a bit when actuating the locks, however the alarm seams to be arming correctly and the doors will stay locked.

Unfortunatly, the alarm is still going off after about 10 minutes of being armed.

Thanks again for listening!

Andy

darth

Andy

What I did to disable each switch, was with masking tape I held them in the "in" position to ensure they didn't make contact with chassis ground. All these switches are doing if you look at them, is connecting a single wire to chassis ground when the door is opened. Somehow you have to ensure they don't make the connection to ground in order to elimnate each switch as being defective. Then I armed the alarm. If the alarm didn't trip after a period of time I went to the next switch and did the same. I ended up disabling each switch and the alarm still went off. Then I found that the green wire was the culprit - either the inner green wire was touching the outer sheath which is in effect the same as chassis ground or it was comming into contact with the chassis itself. It was cut off by the previous owner and left hanging behind the dash which on windy days caused the alarm to go off more frequently. I presume the wind was somehow getting into the car and moving the wire causing it to short to ground and in turn setting off the alarm. Once I insulated the inner green wire from both the chassis and the outer sheath the problem was solved. You may find it is one of your switches. Thru this procedure I also found that the glovebox switch had been disconnected probably due to a buletin sent out by Porsche to address a false alarm in the glovebox.

Hope this helps
Bill
90C2

anewbill

Bill,
Thanks for the reply. I'll give the masking tape idea a try. I still have the original radio installed, so I hope my green wire is still intact.
Andy

anewbill

Update:
Here are the things I've done so far to track down the alarm issue. Unfortunately, nothing has worked yet. The alarm is still sounding after 20 minutes of being activated.

1. Removed radio and made sure the "green wire" is well insulated
2. Removed driver's side door panel and disconnected the central locking wire.
3. Checked all door, glove box, hood, and engine cover switches. (all trip the alarm as designed)
4. Replaced battery

Anyone have any additional ideas for things I can check before taking the car to the shop on Tuesday?

darth

Andy

What MY are we talking about? Did you isolate each switch one at a time to eliminate the possibilty that maybe the switch is defective in that it is falsely setting off the alarm. I know you said each switch sets the alarm but maybe a switch is making contact when it shouldn't. Check for any loose or bare wires (i.e. you should be able to see at least a few inches of wire leading to each switch) while you have the switch out. If you do the masking tape thing I suggested (i.e. so that there is no possible way for that switch to activate the alarm) and you arm the alarm after you've isolate each switch one at a time, wait the 5 to 20 minutes or longer which is the time you say it takes typically to go off. Leave the switch(s) you isolated and move onto the next if the alarm doesn't trip. If you go thru all of them and given them sufficient time to set off the alarm then the switches are not suspect. I left each switch isolated for sometimes hours before I isolated the next just to be sure.

Hope this helps
Bill
90C2

anewbill

Bill,
Yes, I isolated all of the switches one at a time by removing, inspecting and taping them. After some additional troubleshooting yesterday, I believe I have resplved the issue. I resoldered the glove box switch as it was looking a little frayed. Once I reistalled the switch and reconnected the battery, the alarm seemed to be much happier. I left the car locked in the garage all night and was not woken up by any alarms!

Thanks to all for the advice and moral support!

Andy

anewbill

Doh! Got home from work tonight, locked the car in my garage, 20 minutes latter alarm started blairing. Unlocked the car, relocked it and waited 1 hour... no alarm. Unlocked again, relocked it and still no alarm after 2 hours. Off to the shop tomorrow to see what the hammer says.

shesminetoo

Andy,

Does the LED's on the lock stems flash normally? If it flashes twice a second it means that it is picking up a fault. Mine did that and I had it fixed today during the annual service at Porsche Centre. It turned out to be the radio, "green wire". Curiously enough, whenever my alarm armed correctly, i.e. the LED's flashing once a second, the hooter went off after about 5 to 10 minutes. This happened perhaps one in a hundred times. Most of the time it indicated a fault, flashing twice a second, but at least didn't cause a racket.
Reg's

anewbill

Frans,
Yes, the LED's are flashing normally. I took it by the shop this morning and had the faults codes read and cleared. Nothing really looked out of the ordinary as most of the faults could be atributed to my testing over the weekend. My engine cover switch was not turning off the light until the very last mm of clearance when closing the cover, so we replaced the switch to see if that was causing the problem. Hopfully, that will do it.

darth

Andy

What year is your 964?

Bill
90C2