Mostly when armed, the alarm horn on my car is going off for no reason, sometimes even when I think that I have it unarmed! This just started for me on my '96 (Immobilizer) in the middle of my road trip to Lake Arrowhead this weekend. Had to leave the car unlocked for long periods.

Last time I armed it just recently, the LEDs were blinking evenly every two seconds or so. No 10 second gaps or double flashes.

Any advice would be appreciated, even just to make sure it's disarmed. It seems just opening a door may help. All of my lights work and I assume that they go off as well: trunk, glove, domes, engine. Radio plays fine. Thanks!

 

How old is your battery?

A weak battery could cause odd behavior. I have a voltmeter you can borrow.

lights and radio will work even with a weak battery, light will be a little dimmer, and you may not even notice.

 

Have a similar problem and wondering the same thing. And my battery is new.

 

most car alarms have pin switches on the hood and trunk. On a factory alarm, they are usually tied into the circuit that activates the light in either. The pins can get misaligned or worn down and not work properly. It is also not obvious that the light is still on in your hood or trunk, when it is closed and latched.

I would look at those circuits next if the battery is providing full voltage. (which even a new battery may not be providing)

 

Robin posted the list of alarm triggers from the workshop manual. If your alarm is triggering fairly regularly then you could work through that list. Many of them can be disconnected then reconnected one at a time to see if they are the cause.

The switches for the hood and trunk are in the latches. They can be removed from the system by disconnecting the electrical connector. You can leave the glove box door open (bulb out). The alarm system will show a fault (double blink) but the alarm will work ignoring the glovebox circuit. The radio wire (infamous green) must be isolated. It should have some kind of insulation covering the wire/terminal on the end.

 

That link should come in handy. Will try that.

 

If you can get a hold of a PST-2, you can read the codes and status of the alarm system - that will tell you what triggered the alarm.

 

Thanks for the suggestions. It turns out that my Optima Yellow top is about 7 years old. Voltage measured is as follows:

- While on the cigarette lighter charger: 13.37
- Off charge, one minute later: 13.07
- Off charge, 4.5 hours later: 12.90

It doesn't seem like there are too many cases of low voltage problems. Since Robin suggestions include taking the seat out, I think I'm going to find someone with a PST-2 and be done with it.

 

Lomita 911 is my closest shop, so I took the car down to Dieter and Hans (real names, even though it's Hollywood) to take a look. They enlisted the help of our own Lorenfb, who determined that the radio was not getting consistent power. Radio was removed, contacts cleaned and replaced. Fortunately, I knew where my radio code was. Entered it and all is good!

Cost was very reasonable and I was even allowed to pick the car up after 5:00. Never been to Lomita 911 before, but at this point I am definitely a fan!

 

I have known Dieter for about 20 Years. Good guy. He originally worked at Vasek with Alwin, Arnold and 2 other Dieters, of course the first 3 went on to form ANDIAL, the other Dieter had a shop in HarborCity also.

Did Derick look at your car?

 

Derek has moved on to Porsche Motorsport NA in Santa Ana.

 

Good for him! His a good guy. He can put his technical skills to good use there. He would have fit in at Callas also.

 

If it is intermittent, as it is on my car (sometimes won't go off for several hours, or not at all, and one time it took only a minute) how does a PST-2 detect anything? Seems like it needs to be going off for the tech to find the problem. This just started in the hot DC area weather. And yes, I tried it with top up and down, AC switch on and off, windows up or down, open and close the trunk and hood, ...I will check the radio cable since I put in a remote CD changer in the trunk myself (hmmm) a couple of years ago. Infamous green wire you say?

 

oh, hold on. A PST-2 will read the history of codes for alarm activation? I have decent OBD2 reader but I don't think this will help. I use it for clearing ECU when the damn dash engine code light goes on due to SAI clogging.

So what is a PST-2?

 

dcdude has been helpful, and I may take car to dealer to check the alarm history. I have cleared the ECU once in the middle of this problem time, but not in last couple of alarm triggers.

What I did not make explicit is that the damn thing sometimes goes off even when the car is NOT LOCKED. I wonder if the root cause is in the actual car switch- you know, where you put the key and turn. It has an electric component that is known to go bad, and mine IS bad since the dealer bypassed part of it years ago to allow the car to start! (I do not get the little immobilizer light on the dashboard gauge as a result.) Although this worked well for years, it may be the root cause. Any analysis of whether the alarm going off with car unlocked must be due to other than the usual culprits noted above (and which I think I addressed on my car)?