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Blinkers flashing, alarm problem?


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2001 996 C2 Cab. When I activate the alarm I frequently come back and find the blinkers (hazard flashers, turn signals, you know what I mean) flashing. Alarm siren never sounds (not that I have ever heard). When I unlock the car the flashers stop.

This has happened both top up and top down, and only when I activate the alarm. Alarm seems to activate correctly (no beep warning). And it seems to be a new problem this season. No changes to the car, other than replacing the horns late last year (and the horns seem to work fine).

Any thoughts on what might be wrong?

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Interesting. I will try locking with the key. I did recently change the battery in the key remote.

Are the flashing blinkers used to indicate the alarm was triggered or a fault? I just read about watching the red alarm indicator, so I'll have to see if that starts double flashing the next time.

What happens if you lock it by key?

If it works fine with the key it might be the remote - battery or coding.

A PST2 can read the codes for the alarm system which should tell a tech exactly what the problem is.

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The system goes through a series of tests as it "sets" the alarm. If during one of those tests a criteria is not met then an alarm readiness state is displayed (i.e. rapid flashing, double-flashing, on, off, or normal flashing). Rapid flashing means that the alarm system is not "primed". Unlike the signal most folks get with an open zone (single horn beep when a zone is open) the rapid flashing would indicate that the alarm did not succeed in reaching the readiness state.

Again, if it works with a key then it is likely either a battery (bad battery or poor contact) or even a sticking button on the remote.

BTW... you said rapid flashing not double flashing... right?

They mean different things.

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Loren - what I intiially reported was about the cars hazard lights flashing.

I did not pay attention to the alarm system LED at all. Now I will start watching that (I'm sure that observers will think I am just lusting after my vehicle...).

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One more question - I noticed that when I press my key remote, the red LED flashes fairly quickly (maybe 4 times per second or so) - is that the proper behavior?

The system goes through a series of tests as it "sets" the alarm. If during one of those tests a criteria is not met then an alarm readiness state is displayed (i.e. rapid flashing, double-flashing, on, off, or normal flashing). Rapid flashing means that the alarm system is not "primed". Unlike the signal most folks get with an open zone (single horn beep when a zone is open) the rapid flashing would indicate that the alarm did not succeed in reaching the readiness state. 

 

Again, if it works with a key then it is likely either a battery (bad battery or poor contact) or even a sticking button on the remote.

BTW... you said rapid flashing not double flashing... right?

They mean different things.

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The alarm has it's own horn. It is not the same as the horns when you push on the steering wheel. The alarm horn is the round metal silver thing next to the battery on the drivers side. The steering wheel horns are behind the front bumper cover on the passenger side. Sounds like your alarm horn is dead and that is why you only see the flashing lights in the front and rear of the car when it goes off, and not also the alarm horn.

Disconnect the connector to the alarm horn and hook up a volt meter. Arm the alarm then set it off and see if the voltage jumps from 0 to 12 volts in sinc with the flashing lights. If it does then replace the horn.

Then you have to figure out why the alarm is going off by itself.

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Yep - just checked and the alarm horn is dead. So I guess I will have to check voltage to verify it is the horn (as per your suggestion). Then its off to the local repair shop to pull the error. Thanks for all the help.

The alarm has it's own horn.  It is not the same has the horns when you push on the steering wheel.  The alarm horn is the round metal silver thing next to the battery on the drivers side.  The steering wheel horns are behind the front bumper cover on the passenger side.  Sounds like your alarm horn is dead and that is why you only see the flashing lights in the front and rear of the car when it goes off, and not also the alarm horn.

Disconnect the connector to the alarm horn and hook up a volt meter.  Arm the alarm then set it off and see if the voltage jumps from 0 to 12 volts in sinc with the flashing lights.  If it does then replace the horn.

Then you have to figure out why the alarm is going off by itself.

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If the alarm horn is dead and the lights double flash then it is likely an open zone. Most common open zones are: the center console lid not shut tight (or the microswitch is broken), then microswitch for the front trunk, or 3rd party radio installed without covering the alarm trigger point. It could be this simple.

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Sorry, bad explanation on my part. The alarm horn is dead but the alarm light just normal flashes when I turn the alarm on. I double checked that it does activiate properly, and alse verified that if I leave a zone open that it is detected.

I am assuming that when I come back to the car and find the flashers going that the alarm has been set off, so I will need to track down why it is going off randomly.

If the alarm horn is dead and the lights double flash then it is likely an open zone. Most common open zones are: the center console lid not shut tight (or the microswitch is broken), then microswitch for the front trunk, or 3rd party radio installed without covering the alarm trigger point. It could be this simple.

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Well I might be a bit confused as we need to distinguish what flashing lights you are talking about. I assumed the red flashing LED on the dash worked, to let you know the alarm is set. When the alarm goes off it flashes the bulbs in the head/tail lights, and is supposed to make the alarm horn go beep beep.

If the alarm horn is bad then when the alarm goes off then all that happens is the bulbs in the head/tail light blink. I replaced the alarm horn on a Boxster that did this. I first tried to fix the horn by turning the sealed adjustment screw on the side of the horn but it sounded like crap. It is just a VW horn and does not cost much.

If you replace the alarm horn and the alarm goes off for no reason then you have a second problem. Except this will be a noisy problem with a working alarm horn. I just hope is is not a bad alarm control unit as they are expensive.

You said you had the horns replaced last year. Which horns?

For others, the top black horns are for the steering wheel. The round one below is for the alarm.

post-4-1113858932_thumb.jpg

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Just tested the alarm horn voltage, and it goes from 9.6 volts up to 11 volts or so. That doesn't sound like good news - dare I guess that I look to the alarm control unit next?

Re: the other horns, I replaced the Porsche horns with the Griot European horns. They are way louder.

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You got me curious so I hooked up my digital volt meter to the alarm horn connector. This is a January 1997 Boxster. I had the meter connected for all 3 tests.

(1) With the alarm not set there was a constant 9.1 volts. No key in the ignition. I am suprised. I do not know why there would be voltage present if the alarm is not going off. So your car is the same as mine.

(2) I then set the alarm, confirmed it was set by the blinking red dash light, and voltage was 8.9.

(3) Then I opened the inside door to set the alarm off, which I could tell by the blinking head/tail lights. Voltage was pulsing between 11.1 - 9.5 in sync with the flashing lights. No horn beeping because I removed the conector for this test.

You must have a bad horn so replace it. Either that will solve the problem or you are going to have a noisy car if the false alarms continue.

I wish I knew if a bad horn is related to "false" alarms, as if the flashing lights are to let you know that the horn does not work. The Boxster owner did not tell me if he was getting false alarms when his horn went bad. But then, I did not ask how he knew the horn was bad.

post-4-1113934147_thumb.jpg

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That is a huge help - I am off to buy a new alarm horn. Then I'll have to tackle the false alarms... Might be time to get PSE put in while I get the alarm diagnosed!

Edited by trauh
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The 9 volts is just an open-circuit 'floating' voltage that is a symptom of how the alarm horn is controlled by the alarm unit. The 9V is shunted by the horn when it is connected. (Horns are surprisingly heavy current consumers and therefore quite a low resistance)

Incidentally, on later model cars, there is an alarm siren as well as an alarm horn. So it 'screeches' as well as 'toots' when the alarm is set off. However, if a zone is left open you just get a single 'toot' from the horn.

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All fixed. With continued observation I noticed that the alarm system led did sometimes cycle into the double flash indicating a fault. Yesterday I picked up the new alarm horn and 5 minutes later it was installed. So far it works like a charm. Horn beeps, and the system arms correctly (which I now believe it never was doing).

Crossing my fingers that it stays that way. Loren and Toolpants and others, thanks so much for the guidance. This board rocks!

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  • 2 weeks later...

Dear Friend,

I currently have this same problem in my 98 Boxster. So by replacing the horn the false alarms quit? I sure hope this should be it.... :rolleyes:

All fixed.  With continued observation I noticed that the alarm system led did sometimes cycle into the double flash indicating a fault.  Yesterday I picked up the new alarm horn and 5 minutes later it was installed.  So far it works like a charm.  Horn beeps, and the system arms correctly (which I now believe it never was doing).

Crossing my fingers that it stays that way.  Loren and Toolpants and others, thanks so much for the guidance.  This board rocks!

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This intrigued me. Could the floating 9v and the resistance of the horn (assuming it is not O/C) be used to sense the horn. If so then it makes sense. A faulty horn would show up as a fault in the alarm circuit and the lights would flash.

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