Central locking (Audi 80 B4)

All doors, as well as the trunk lid and fuel tank cap, can be closed by turning the lock switch on the driver's, passenger's or trunk's door. The basis of the central lock is a dual-function pressure pump driven by an electric motor. When the lock is turned to position «Open» this pump builds up pressure, under the influence of which the central locking switches unlock the corresponding lock. To lock the locks, the pump creates low pressure (see illustration 20.0).

Attention! The trunk lock has its own characteristics. If the key hole in the lock switch is vertical, the trunk lock is locked and does not respond to the central locking. This is one way to protect against thieves. If the hole in the switch is in a horizontal position, then the trunk lock «obeys» central lock.

Central locking - check

1. Open or close the driver's or passenger's door lock or trunk lock with the key. The central locking should work when locking/opening any of the specified locks and after about two seconds all locks should be closed.

If the pump continues to operate for more than five seconds, then the central locking system is leaking. In this case, the dual-function pump should run for no more than 35 seconds. After this time, it should turn off.

Attention! If the central locking does not work, then the door and trunk locks can be opened and closed with a key. The lock switch buttons can also be opened and closed manually.

If the pressure pump when turning the lock switch of one of the doors (driver, passenger or trunk) does not work, then to check the electrical part of the central lock, do the following:

2. Check the appropriate fuse.

3. Remove an upholstery of a back right part of a luggage carrier.

4. Remove the central locking pressure pump and disconnect the multi-pin power plug of the central locking switches (see illustration).



5. Loosen the clamp and remove the rubber cuff from the plug.


6. Check the central locking switch on the driver's door (see illustration).



To do this, connect the tester with a control lamp to the plug contact to which the wire with green-blue insulation is connected, as well as to the wire contact «masses» (-) on the body. The control light should be on constantly when the driver's door is unlocked with the key. This means that the opening contact of the central locking switch on the driver's door is OK.

If the control lamp of the tester does not light up, then the opening contact of the central locking switch on the driver's door is faulty or there is a wire break.

7. Change the connection of the tester with a control light. Instead of connecting to a wire contact «masses» (-) Connect tester lead to (+) battery. The second wire of the tester remains in the same place - on the contact of the plug, to which the wire with green-blue insulation is connected.

8. Lock the driver's door with the key. If the control lamp is constantly on, then the locking contact of the central locking switch on the driver's door is in order. If this is not the case, then the locking contact is faulty, provided that there is no wire break.


9. Check up the switch of the central lock of a passenger door. To do this, connect the tester with a control lamp to the contact of the disconnected plug, to which the wire with yellow-blue insulation is connected, as well as to the wire contact «masses» (-) on the body. The control lamp should burn constantly at unlocking of the lock of a passenger door by a key. This means that the opening contact of the central locking switch on the passenger door is OK. If the control lamp of the tester does not light up, then the opening contact of the central locking switch on the passenger door is faulty or there is a wire break.

10. Change the connection of the tester with a control light. Instead of connecting to a wire contact «masses» (-) Connect tester lead to (+) battery. The second wire of the tester remains in the same place - on the contact of the plug, to which the wire with yellow-blue insulation is connected.

11. Lock the passenger door with the key. If the control lamp is constantly on, then the locking contact of the central locking switch on the passenger door is in order. If this is not the case, then the locking contact is faulty, provided that there is no wire break.

12. Check the central locking switch on the trunk. To do this, connect the tester with a control lamp to the contact of the disconnected plug, to which the wire with brown-green insulation is connected, as well as to the wire contact (+) from the battery. The control lamp should be on when the trunk lock is unlocked with the key. This means that the opening contact of the central locking switch on the trunk is OK. If the control lamp of the tester does not light up, then the opening contact of the central locking switch on the trunk is faulty or there is a wire break.


13. Change the connection of the tester with a control light. Instead of connecting the green/brown wire to the terminal, connect the tester's test lead to the brown/white wire. Connect the second wire of the tester to the wire terminal (+) from battery

14. Lock the trunk with the key. If the control lamp is on when the key is in the lock position «Closed», then the locking contact of the central locking switch on the trunk is OK. If this is not the case, then the locking contact is faulty, provided that there is no wire break.

15. Check the pressure pump. If the central locking switches work (see above), then the reason for the failure of the pressure pump may be a lack of power. Check the integrity of the thin wire with black and blue insulation and the thick wire with red and black insulation, as well as the wire «masses» (-) (thick wire with brown insulation). If they are in order and power is supplied to the pump, then the pressure pump itself is faulty.

16. Replace pressure pump (see illustration).



To eliminate leaks in the pneumatics of the central lock, which manifests itself in slow operation of the central lock and too long operation of the pressure pump, it is necessary to check all the elements of the pneumatics in order, and in particular the places of their connections.

17. Pressure pump. Pinch the hose near the pump with pliers and lock one of the locks. If, when the central lock is activated, the pressure pump runs for more than three seconds, but not more than 7, then it is leaky.

18. Replace pressure pump.

19. Check the central locking switches on all doors and on the trunk lid. To do this, disconnect all hoses in order next to the switches. To gain access to the hoses, remove the appropriate lining. After disconnecting the switch hose, lock one of the doors. In this case, the charge pump should operate for no more than 3 seconds, maximum 7. When a hose with a defect is disconnected, the charge pump will start to work in normal mode, i.e. within less than 3 seconds.

20. Replace the defective element of the central lock.