VW T4 AAB Voltage Drop and Relay Clicking After Start

Verify the symptom by measuring battery terminal voltage with a digital multimeter. A normal state is 13.5V-14.7V while the engine is running. A drop below 13V or erratic fluctuations indicate charging instability. The clicking sound signifies a relay, such as a split-charge or glow plug relay, rapidly cycling due to low or unstable voltage threshold triggers.