How to connect aftermarket alarm with factory central locking Hyundai i20

SOURCE: Disable or disconnect the factory installed alarm

should be a fuse for it, just remove it......

SOURCE: central locking on citroen xsara 2003

We have this problem too - can only lock the doors by shutting front doors - climb into the car via the back doors - lock front doors from inside and then manually lock back door. Boot is difficult to lock - takes about 3 or 4 attempts to lock it. Driving me mad!! Have been told it is probably worn or broken wires in the flexi hose in the door hinge. I may have to take it to the garage to get repaired.

SOURCE: car starter not working

look under the dash for a small silver toggle switch....this is a disable switch for the remote start portion of the system..you may have kicked it / bumped it with your foot, causing the remote start portion to be deactivated. Just flip the switch the opposite way and try again..
Also, there may have been a pin style switch installed under the hood...Check to see if it is bent or broken, if it is, simply disconnect it and insulate the wire that was going to it. 
This wire is used as a safety to keep the vehicle from remote starting while the hood is up..to keep people from being injured if the remote start is activated while the engine is being worked on. 
Have whatever shop installed the system replace your pinswitch if that is the problem.

SOURCE: ford fiesta ghia 1998 model central locking key

This is a common problem after changing the Key Fob battery.

The solution is to remove the fuse feeding the Cental Locking for 10 minute...Replace then all should work fine

SOURCE: my prestige car alarm keyless entry will not

have you checked the 3 pin door lock plug at the alarm? it may be loose or unplugged totally.