09 Boxster S alarm and horn issue

[Crankgrinder]

Hi, got a issue with my alarm/horn

Alarm has been going off in garage for no reason when both locked or unlocked. when it goes off both siren and main horns just blare out. has had diagnostic check which showed no issues !
Been disconnecting battery when in garage, but last week on connecting main horns blare out and cannot stop with key, turn twice in door etc. taking horn fuse out does not stop it.
anyone experienced this or got any idea's ?

 

[½cwt]

Usually a sign that the battery is toast. Fit an 096 or 110 sized battery from a decent brand. Bosch Yuassa, Varta with a decent guaranty on it. Also, if you park in your garage consider a CTEK battery conditioner. These are good for cars that are not used so frequently.

 

[deMort]

Alarm siren , water under the passenger's seat due to a blocked drain tube and coins in the ashtry are some things i can think of ..

Pull the carpet up behind the rear passenger seat and make sure its dry , unplug the siren and remove coins from the ashtray would be the first steps .

With a tester we can see events and actuations , one is the fault with the car when locked and the other is what has triggered the alarm .. these both need checking .

The car alarm for a C16 ( UK model ) should Not activate the horn as well as the siren with an alarm actuation .. therefore to me its water or a software / siren issue .

 

[½cwt]

Ah, yes, the costly problem.
Check for blocked rear drains, water going down the rear bulkhead inside the cabin, or a wet bottom to the passenger door card which could let water on if the door membrane is split or has been badly re fitted.