Latched relay?

A few more details about the switch would help. ]

As I understand it you want a Relay to flip the motor wires from positive to negitive and rest then switch from negitive to positive then rest whenever a pulse is put on lock or unlock.

By "hit or miss" do you mean the switch has a problem? or the vaccum? You didn't mention the year but I used to do alot of these type locks on the older benzes..looks very similar. The problems i would find usually lead to the vacuum lines dried out and leaking so they were not consistant. Normally the "switch" is the doorlock itself..does this vehicle have a regular toggle somewhere or only works off the doors (central locking)

If the problem is the switch..you may need a new one. The best bet on those older ones is to replace all the vacuum locks for electric actuators..you can even use a central locking system which allows the front door locks to control the rears...as well as using your keyless entry.

Post back if you have more info..I don't fully understand the problem.

I think I finally understand this. It would help to know the year of the car but if it's an older vacuum locks it requires an extended pulse to operate properly..a relay will not fix this.

You need to check the programming menu of your security system to see if it has a feature to extend the doorlock pulse. If you don't have a menu (should be in the installation manual) post the make and model of the alarm and maybe we can get the info.

If your unit is not programmable for this they sell pulse extenders for this very purpose. They are cheap so it's worth it rather then building your own..which is another option.

The timing cycle on this circuit is the same as the previous.