Im installing an aftermarket alarm on a 97 Nissan Primera. When I conncet the two cables for the central locking all the doors bar the drivers door lock/ unlock, the car already has remote central locking so I don't need to install another door motor, what am I doing wrong?

Not knowing anything about the alarm's interface, some are positive trigger, some negative, some are contact closures. Usually the outputs are momentary. e.g. momentary lock, momentary unlock

You may have to provide diode isolation (usually two) or at least an external relay..

Are you activating the car's lock & unlock relay or are you trying to activate the motor directly?

When I did my alarm, I added a switch in the passenger compartment such that I could optionally open the passenger door on unarm.

Thanks for your answer,

The alarm outputs are momentary negative outputs which is what the standard central locking uses. I have connected it straight to the lock and unlock relay - just doubled up on the inputs from the lock unlock switch on the drivers door. The system works fine for all the doors and boot when you arm disarm the alarm but for some reason the drivers door doesn't lock or unlock with the rest... tho if you use the key or the door switch all doors are working.

Ive tried testing all the other connections on the relay to see what happens when I use the door switch as compared with the alarm remote and the inputs/ outputs from the relay seem the same.

Any help is appreciated!

Hey have sorted the problem if anyone else needs it the prob was,
The drivers door actuator was controlled by its own relay compared to the rest of the car, and the only way to trigger that relay was with the standard c/l remote. So to get working with the rest of the car I just had to find the actuator outputs on the relay for the rest of the car and run new cables looping them to the outputs from the drivers door relay. Then unplugged that relay. Now when I use my alarm remote all doors working fine. And if I ever want to use the standard controller just need to plug the relay back in and disconnect the jumperleads I ran.