problems with a car that has been without power

[datmbn]

I have had the car (GT 2007) parked over the winter and in order for the battery not to discharge, I have lifted the earth cord on the battery.
When I was going to look at the car yesterday and plugged in the battery, the horn started howling with a persistent tone that did not stop until I
started the car, but as soon as you turn off the car the horn starts again and the instruments flash as if the alarm is on the horn sounds with
a persistent tone and the light also shines with a steady light
Everything else seems to work, you can unlock the car, both the cabin and the luggage. and it is perfectly possible to drive
Does anyone have any idea what the error might be?
I also tried to reset the alarm with the small button on the red light on the steering column.

 

[eighty6gt]

small button the red light on the steering column?

You'll want to clarify if you have an aftermarket alarm system. I've never seen a good one.

 

[07 Boss]

How was the car parked? Did it get rained on? SJB water intrusion is where I first look when the electrical starts acting wonky.

 

[datmbn]

I do not think it has an aftermarket alarm
And it has ben in an perfekt dry barn with an konkret flor so No water

 

[datmbn]

The car was in for airbag replacement on the passenger side 2 days before I put it away, and then they must have been toreing near she SJB, considering how sloppy the "Sweden conversion" at the headlights was done, it may very well be a splice sleeve or power thief behind sjb who gave up.

I have to drive the car home and redo the "sweden conversion" behind sjb as well (use soldering iron and tin, as well as shrink tubing and vulcanized tape

 

[JimC]

The stock alarm doesn't have a 'red button' so you must have an aftermarket unit installed.

 

[datmbn]

After further investigation I may have an aftrmarket alarm

Maybe I hawe an aftermarket alarm that have come out of synk .
I will try to conekt the battery withe the car lockt maybe it will work

Speaking of alarms that have get out of synk
A few years ago I had a car with an alarm that you had to learn the remote control every time the car was without power, and it was done
by first locking then unlocking the car, at first locking / unlocking, the alarm learned the remote not so safe but smooth.
One night I had changed the starter motor on that car and did not think about learning the remote so the next morning when I opened the garage door with the garage door remote the car was locked
and the garage door opened so there I stood with the car locked and the garage door open, when I then pressed close on the garage door the car was unlocked.
It was just to disconnect the battery, wait a few minutes and then start again.