Good morning, I know this topic has been covered many times but I just really want come sort of confirmation that my thinking is good before I spend any money. The alarm went off last night on our 2009 1.9 Octy. It seems to go off every few months for no reason. Anyway, I got my VCDS plugged in and checked on the activations. The current activation was code 22 (back up horn) and the last three/two were all Interior monitor. The last ones were in the summer so likely to have been a spider or fly, so I'm not worried about that. But it was -1C last night, so cold, and the back up horn activation sounds like the battery in the thing is dying. (main battery voltage was 12.5 after standing all night so I don't suspect that) I think I have to buy another alarm/horn unit, do you agree? I bet they are expensive if genuine, any cheaper substitutes available? Failing that, I wonder if I could just unplug the alarm and forget it. The immobilizer is the important thing I would say and the car isn't worth a great lot. Thanks. 

I would say the battery in the alarm unit it end of life. You can usually find genuine replacements on eBay around £35.

 

You can cut the old one open and replace the battery pack with something similar but you need to solder onto the board and reseal the casing and find a cell pack that will fit.

 

Also if the battery has leaked it can damage the board.

 

Yes you can unplug the alarm unit. Main downside is that if someone breaks in there is nothing to scare them off...

I have the same problem with my Octavia.  My garage (not a Skoda dealer) advises that it is poss to 'unplug' the alarm whilst retaining the immobilizer as '...this is in the key'.  He also suggested locking with the key as '...on some cars this will not arm the alarm'.  Is this true of Octavias?  I cannot find a plan of the fusebox which identifies which fuse covers the alarm and/or specifies what else that fuse covers.  Can anyone help?

Have a look at the link below and enter your car model year for access to Skoda's Owners Manual for your model, including fuses.  Note that fuse allocation does vary slightly between some model years.

 

https://manual.skoda-auto.com/004/en-com/Model/Octavia_1Z

 

Locking the remote button twice or pressing the button on the bottom of the drivers b pillar deactivates the motion sensor but not the alarm in entirety AFAIR. 

Many thanks for this.  I have now located the fusebox which is in the RH end of the dashboard and not the LH end as in the manual!  The manual says that fuse 35 serves the 'Anti-theft alarm system'.  I have identified the location of fuse 35 on the chart contained in the fusebox and found the relevant socket in the fusebox BUT there is no fuse fitted!  Any further help would be much appreciated as I now only want to immobilise the alarm.

The fuse layout in the manual and on the cover is a mirror of the actual fuse holders.

 

5 row down, 4th fuse back (to left of) from firewall. Should be 5A.

Did you check the Owners Manual for your exact model?  Use the build date from your VIN.

 

For some reason Skoda changed the fuse panel assignments around the 07/08/09 model years.

Many thanks to each of you!  I will try again tomorrow.  Presumably Skoda made pointless changes to the fuse layout for the same reason that they used a mirror image in the box and the manual - to ensure that only expensive main dealers could solve problems....?   

Just to add to thia my Octavia does the same, alarm randomly goes off!

 

SUCCESS!  5 rows down/4 sockets back from the firewall was indeed a 5A fuse which I have removed.  Difficult to positively prove that I've killed the alarm but everything else still works so time will tell.  I assume the immobiliser still works as my garage says "It is in the key"  Is that true?  Many thanks again to each of you for help.   

You can check if the alarm operates by locking with Windows open. Leaving it a minute then put your arms in the car and wiggle around. That would normally trigger the alarm.

 

The immobiliser should be still active.