Volkswagen Repair: 99 VW Cabrio Keyless problems, vw cabrio, oxnard st

Question
I recently purchased a '99 VW Cabrio. The 2 keyless fobs that came with it will only work to unlock the door and trunk, but only if used with the first 30 seconds of locking the door with the key. After about 30 seconds after locking the door the horn will chirp and the remotes will no longer work at all.
Also, if you close the door and press the lock button on the fob the LED next to the button flashes right away, the doors do not lock and after about 30 seconds the horn chirps and the remote does nothing.
I have tried re-programming the remotes and it is the same.
I know that the vacuum unit does work to lock and unlock the pass side door when using the key in the drivers door and since I do not have the service manual I am unsure if the driver's door operates off of vacuum when using the remotes?

Any ideas?

Thanks,
Jack

Answer
All the power door locks work off the vaccum pump in the trunk. If the vaccum pump is malfunctioning it will mess up the entire system including the alarm. Otherwise, my next guess would be to check the actual lock-latch assembly. These assemblies do wear out over time and also will definitely affect the alarm and power lock system. Third would be to check the alarm module underneath the dash near the light switch(right behind the light switch). I am Max's German Car located at 15020 Oxnard st Van Nuys CA 91411. I have all of these parts used. The vaccum pump is $35;the door lock-latch is $65;and the alarm module(I would need a part number)is $65. CALL: 818-787-9138; I take credit cards and ship.