33. Switch the ammeter with a measurement range from 0-5 mA to 5 A to the upper range.
34. Disconnect the ground (-) wire from the battery, after turning off the ignition.
Attention! If the radio has an access code, then disconnecting the battery deletes this code. After connecting the battery, the radio can only be turned on after entering the appropriate code or by using the services of an AUDI workshop or the manufacturer of the radio. Therefore, before disconnecting the battery, check and write down the entered code.
35. Connect the positive (+) lead of the ammeter to the negative (-) battery terminal of the ground wire, and the negative (-) lead of the ammeter to the negative battery terminal.
Caution: When checking the battery on diesel vehicles, remove the glow plug fuse (preheating), to avoid damaging the ammeter with high current.
Attention! The test can also be performed using a test lamp. But if the lamp connected to the ground terminal and the negative pole of the battery does not light, then you must use an ammeter in any case.
3S. Turn off all current consumers, turn off the clock and other constant consumers of electricity, close the doors.
37. Switch the ammeter to smaller and smaller measurement ranges until the ammeter reading can be read (1-3 mA is acceptable).
38. Disconnect various electrical circuits by removing one fuse after another. If the ammeter readings drop to zero when disconnecting a circuit, the fault should be sought in that circuit. The sources may be corroded or dirty contacts, frayed wires, or an internal short circuit in the circuit.
If no fault is found in the circuits protected by fuses, the wires must be disconnected from devices without fuses, such as the generator and starter.
If the instrument readings drop to zero when disconnecting any of the units not protected by fuses from the terminals, then disassemble or replace the corresponding device. If there is a loss of current in the starter circuit or in the ignition system, it is necessary to check both the ignition switch and the starter according to the diagram.
39. Connect the ground (-) cable terminal to the battery.
The article was copied from the website: AUDImanual