I recently changed the windscreen wiper motor/linkages for similar one bought via eBay. The new (used) one works fine; however since then the alarm system is playing games with me. In short - locking the car via remote locks all doors and 4 flashes on the hazards. 10 seconds later, all hazards start flashing and stay flashing. Single button push (on key) makes the flashes stop but the car remains locked. Second push on the key button then unlocks the car ready to start. If the car is locked using the remote, it seems to me the alarm is not activating/working as opening the car using the key should trigger the alarm siren. Similarly a long push on the remote's button should, so the manual says set off the siren in panic mode - it does not.

Before the wiper motor change the car behaved itself. A single remote push would lock the car and set the alarm. Only the locking function now works.

I've taken the siren horn out to maybe see if it's battery is OK. Previous car had openable siren horn and a replaceable 9v battery. This horn has no obvious way of getting to the innards. I'm stumped.

Anyone with ideas? Has this syndrome happened to you before and if what did it take to resolve? Lastly, since the condition has only arisen after I changed the wiper motor/linkage could it be that somehow (??) the car has decided it doesn't want the replacement unit? Unlikely I know but grabbing at straws.

Appreciate your help.

Did you disconnect the battery before working on the wiper linkage?
If so, then this is more likely the cause of the alarm being out of sync.

Alternatively, it may be worth following your work in reverse in case you missed something (done it myself loads of time)

Thanks. I forgot to disconnect the battery before swapping the wiper motors but did a disconnect after, and again when I found the problem but still no cure as yet. Any idea which fuse is used for powering the Sigma alarm system, as the provided fuse panel layouts dont have this system listed?

As far as checking the work I did, nothing to report. Simple unplug one wiper motor, plug in the other one. No other electrical work done at all so nil for me to re-check.

Usually a Sigma alarm (aftermarket fitted) would have an inline fuse for power / ignition feeds but also check a connection has dropped off under the dash

You got picture of remote fob and the siren .
Has the alarm bonnet switch been bent out of position while working on wipers (shouldn't cause exact issues you detailing but best check everything and assume nothing .

Update - I have narrowed the issue down to the bonnet alarm switches. The one under the cowl showed very erratic conductivity when tested with multimeter. Compared to the other one - mounted near the o/s strut tower which showed good conductivity - I swapped them over. The car alarm system seems to be behaving itself, despite the dodgy one still being in the circuit. I now need to source a suitable replacement. Any thoughts based on the picture?