SC Factory Alarm - Issues / Solutions

[jwernquist]

The Factory Alarm Aka - Pandora's Box -
I have been afraid to use my factory alarm since the moment I purchased my car
I remember clearly the PO saying - "This is the Key for the Factory Alarm and here is the spare key for the Factory Alarm, I wouldn't use this alarm until you get home and your car is safely in your garage."

That being said I never used the alarm. However in the middle of the night my alarm went off. I never triggered the alarm. I went out there turned the key on and off and the alarm went off.

Today I went out and opened my door and the alarm sounded for a few minutes. Then went off. I proceeded to put the key in the car and drove off. Went to the gas station and came back home got out, shut the door opened the door and the alarm went off again then shut off on it's own.

I've gone through this thread - Which Applies to a the later Carrera
Factory alarm starting to love my porsche

Haven't found much on the SC.

So step one it sounds to me like my problem is in the switch mabey a loose contact on the back of the switch.

Strangely enough the switch and alarm work fine when triggered with the key.

Any tips for removing the switch and cleaning etc. Can it safely be removed then re-plugged in?

All is well at the moment, however I am a little leery at the current time.

JW

[83-911SC cab]

I tried removing the door switch for my alarm with the battery connected and as soon as I removed one of the wires from the switch the alarm started sounding. I had to disconnect the battery to remove and replace my door switch.

Other than that I had no problem replacing it. I can not remember if the alarm operates properly, for soon after replacing the switch the car went in to the body shop (3 years ago) and I am yet to get it back, but that is another story....

Good luck,

Gregg S

[janz]

After reading your post a few times to get the idea of what is going on I would say that the key switch is bad or you have a wire or connector problem at the switch in the door jamb. I would start there looking for the problem. If none found there then it might possibly be the alarm control itself but my money is on the switch or the wires/connectors in the door jamb. Mine is still working perfectly since the first test and I use it all the time just because its there.

[schoward]

I cut and pasted in this follow-up which I added to an old post of mine (do a search if you want to see history) ...just a possibility for you.......

Go in through trunk and check this little white plastic 2-wire plug I speak of.

Jiggle the wires - if the alarm goes off, that could be your issue. When I said 'no way to stop it', I did not have the keys handy as they were missing (replaced switch afterward). Problem solved for two years now.

OLD POST:

ok it only took a year - but finally solved the problem with my randomly honking factory alarm on my 81SC.

I have heard of others having this problem, which basically causes the alarm horn to sound occasionally while the system is off. It can be quite embarassing and frustrating as there is no way to stop it. And it seems like no rhyme or reason. Sometimes movement or vibration triggers it or sometimes virtually nothing at all. Very wierd and annoying and VERY sensitive. At one point, the 'vibration' from my seat belt light buzzer triggered it.

Turns out the 2 wires that run from the alarm module to the key switch in the door goes through a 2-wire plug along the way to connect the wires coming in from the door key switch (probably to ease assembly of the car). It seems the plastic plug corroded/deteriorated so that the connection was sometimes 'lost' which I presume interrupted the expected resistance from the switch and caused the alarm module to think the key switch was disconnected or tampered with.

The 2 wires are a grey/brown combo and the plug is behind the master cylinder area (near the big plug which plugs in many of the other wires coming in from the door.

In any case, wanted to post this in case any SC owners experience this as it is really annoying and embarassing and something a shop would probably kill you on charges to find.

Oh - and afterward , I replaced my alarm key switch which had no key. Factory Alarm works perfectly. I love it when 25-year-old gizmos start coming back to life.

[Chakka71]

My alarm key turns in the door to deactivate/activate but regardless of its position it doesn't turn it off. I assuming i'll need to take the door apart? Any thoughts or things I should be looking for in the door once apart? Thanks

[kiwiokie]

I have an '83SC with the lock for the factory alarm in the drivers door. I did not receive an alarm key when I purchased the car and I suspect the alarm system has been removed or disconnected. Where do I look for the alarm controller unit? Is there a separate siren that is activated by the alarm or does it use the regular horn? I am turning the car into a minor hotrod so would like to remove any excess wiring that I do not need. Is it possible to remove the factory alarm wiring or should I leave well enough alone? Cheers, John

[LM3929]

The alarm control unit located in the center of the trunk deck just under the Defrost fan unit, the alarm horn is near the fuel pump attached to the alum frt. cross member.


Lorne M.