: The device is maintenance-free. Use a dry cloth to clean the plastic casing; never use solvents. BOSCH KL 1206 AUTODOC

: Always store the device in a cool, dry place away from extreme moisture or temperature fluctuations.

Verify that the clamps are securely gripped onto the terminals and are not touching each other.

The manual likely won't have a full schematic, but many user forums do. One of the most valuable "exclusive" pieces of knowledge is the charger's unique circuitry. The KL 1206 uses a "center-tap" rectification method on the secondary side of its transformer. This circuit uses a transformer with and a single negative. It then uses only two diodes (one on each positive line) instead of the four you'd see in a bridge rectifier. This is an older, simpler design chosen to reduce diode count, with the transformer winding doing more of the heavy lifting.