355 Siren just goes of after car is locked with FOB

Sounds like you have an intermittent short somewhere.

Can you confirm that your door open lights work (individually)? For all we know it could be related to your missing door open buzzer module

A short in a door lamp bulb holder may trigger the alarm. A short in the buzzer module may trigger the alarm, too, if you have one.

 

I'm not sure if removing the door cards will help. Since your lights (on the aft end of the door) appear to be working normally, it's less likely that there's a problem in the door. I just hope the F355s are not going the way of the F348s and the wiring on the door hinge is starting to break and short out.
Maybe your door open switches are out of adjustment. Did you eventually find them (near the lower door hinge)?

 

The only way to know is to read the memory and parameters to see what is happening.

 

Was your car ever showing the correct number of beeps and flashes or did you only notice the irregular beeps and flashes when your car alarm started going off? The new antilift sensor or door-switch-spraying may have stopped the alarm going off, but you may be correct in thinking that the SD tool may need to reset something to clear up the flashing/beeping problem. To me it seems an odd design though.

 

It seems that fear of something breaking might become a major factor in our F348/F355 parts purchasing decisions

I wouldn't throw away your old one, Paul. Someone might want to experiment with it and look into the possibility of attaching a replacement "plunger type NO" switch to the metal bracket.

Not identical, but you get the idea:

https://chnanma.en.made-in-china.com/product/pBdEtGUcqRYV/China-IP65-Panel-Mount-Push-Plunger-Type-Sealed-Limit-Switch-with-Ce.html

10 switches for U$12?

 

Just had a closer look at my switch and I'm amazed at how little the plunger moves when the lid is closed. I'm not surprised that wear and tear would result in the switch not opening when the lid is closed.
As I said before, you can adjust the switch slightly to help with the process.

If your switch is like mine, as a temporary measure, you could depress the plunger on the switch as shown in this photo and jam something non-conductive between A and B (on the underside of the switch)

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This should stop the switch conducting and setting off the alarm randomly. Normally, when the engine lid is open, the pointy part of A inserts into the hole in B allowing continuity.
At the moment, I'm not sure if the plunger itself forms part of the conductive circuit. The mounting bracket is connected to part "A" all the time.

(EDIT: The switch is more robust than I imagined. It's not something which would break easily. Unless the spring on the plunger is broken, I'm sure yours could be repaired by cleaning and adjusting)

 

This is correct. As you say, Ferrari seems to like doing things differently.

If your switch is operating as you describe it, then it should be ok (other than, perhaps, wear and tear affecting the movement of the plunger). Did you try rotating the bracket slightly to put the plunger closer to the part it hits on the latch?

 

Are we all sure the 360 alarm in the 355 is ok

 

I assume you mean the 36o anti-jacking sensor?

 

Aren't these sentences contradictory? Or was the switch intermittent, then finally broke?

 

Yes

 

Shouldnt removing the sensor have the alarm consider it as a open circuit thus not trigger the alarm? I am trouble shooting my alarm as well as the same symptoms are happening, and keeping the circuit open or the connectors from touching doesnt help so I dont believe the plunger in my case is the problem. Did you figure yours out?

 

Is it working now that you changed the sensor?