Relay with pump problem

Hello, I have a Volkswagen Jetta (1988) and it has a vacuum pump central locking system. It is switched using a 3 wire positive system and I have used the diagram for 3 wire + to wire some relays so it works with my Clifford Arrow 3. However, I have a strange problem. When I arm/disarm - the alarm behaves normally but no central locking. If I arm/disarm twice in quick succession, the central locking works. Is there any chance someone could indicate to me why this happens. I am suspecting a lack of current but I am not sure. I checked my settings and they are 3 seconds and double pulse. Regards, monkeytom

It wont lock or unlock, or neither? On newer VW's the Unlock requires a double pulse, but not lock. Try triggering your relays manually by touching the trigger wire to ground a couple of times quickly to simulate a double pulse. Use a fuse in line if you dont feel confident in this procedure. I suggest this because it will help you see what is required to make them work.J Rilla

Owner/Installer

It does both but only every other time. So, lock/unlock fails and then if you lock/unlock soon after it works. It is like it only works if you do it twice. Thanks for the advice though - I'll give it a go.