Audi Repair: Door locks not working, vacuum system, rear doors

Question
bought used 1999 A4 Quattro 2.8 5V, key will lock & unlock drivers door and set alarm. it will not lock or unlock passenger & rear doors. what should I do first?

Answer
If the one key unlocks just one door, then your power door locking system has failed.  I would check the fuses first.  When you lock or unlock the door can you hear a whirring sound from the back?  If so then the power door lock actuating motor is working, but there is a leak in the vacuum system somewhere; more difficult to find but still do-able.  If you do not hear a whirring sound then the power door lock module may have failed, ot the trigger in the door lock is not working anymore.  But go for the fuses first.  Let me know,  Jan