Battery Isolator and Alarm Relationship - Ferrari Life
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post #1 of 6 Old 05-11-2013, 02:19 AM Thread Starter
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Battery Isolator and Alarm Relationship

I've read the dirvers handbook, the alarm manual , the workshop manual and various threads on the alarm system and battery isolator. My 550 is a Euro spec and the alarm is set up to do 5 off 30 second cycles of the siren, when it is triggered.
I have tried on several occaisons now to operate the car battery isolator under the bonnet ( hood) and each time this sets the alarm off and it runs continuously i.e. it goes pasts 5 off 30 seconds of cylces and just keeps going doing 30 second cylces of the siren.. If I reengage the car battery the alarm then stops after 5 cycles as per the manual. The doors and boot lid ( trunk) are closed. The keys are not in the ignition. Only the bonnet is open for access to the switch. What am I doing wrong and what happens when I have to change the battery? Do I just go deaf?
With a low battery, that would not turn the engine , I connected a second battery in parallel with jump leads and started the engine. The engine started but the alarm went off and continued to sound until I disconnected the second battery. The alarm then stopped.
Apart from wearing ear protectors, does anyone have any suggstions?

'97 Rosso Corsa 550 Maranello
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post #2 of 6 Old 05-11-2013, 02:47 AM
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Nigel, can you trace your siren's power cable and determine if it goes directly to the battery's positive & negative terminals, or where it's picking up its power?

Mine is wired directly to the battery, so it effectively bypasses the battery isolator switch (ie the alarm still receives power when the isolator switch is opened and everything else is isolated) I don't know if this was factory wiring or a dealer mod on my 550, but it keeps the alarm happy (and my eardrums intact )

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post #3 of 6 Old 05-11-2013, 08:01 AM
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I have the same effect on my 456M. I can turn the battery switch off without alarm only when the alarm is not engaged. I.e. the car has to be unlocked.

When I store the car during winter and set the battery switch to off, the car is always open.
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post #4 of 6 Old 05-31-2013, 12:42 PM Thread Starter
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Just to close out on this one with the solution.
John, I have not been able to trace all the alarm wiring, but it looks like it has not been wired so as to bypass the battery isolator switch.
As for operating the isolator switch, without triggering the alarm, the solution is blindingly obvious, once I discovered it. The battery must be isolated in the 120 seconds between the immobiliser being disarmed using the key remote and the automatic rearming by the ECU, if the engine is not started. Pass the 120 seconds the immobiliser is rearmed and the siren will trigger if the car battery is isolated.

'97 Rosso Corsa 550 Maranello
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post #5 of 6 Old 05-31-2013, 12:45 PM Thread Starter
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Mehl, I forgot to add it is not just my car must be unlocked,as you mention, I also have to be in the 120 second window, otherwise the alarm triggers even with the car open.

'97 Rosso Corsa 550 Maranello
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post #6 of 6 Old 05-31-2013, 02:55 PM
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Nigel- The system was designed to prevent someone from disabling the battery and then stealing the car. In many Corvettes, thieves would just drill a few quick holes in the side of the battery case, wait a few seconds for the battery to drain, and then tow the car. Glad you figured out the 120 second requirement.

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