Many Euro 5 and almost all Euro 6 vehicles are equipped with an intelligent alternator. In these vehicles, the function of 12 V isolating relays and D+ simulators is either limited or no longer possible. To ensure that the RV battery/batteries is/are charged, a charge booster or BCB must be installed.
In many newer vehicles, it is difficult or no longer possible to tap a D+ signal directly from the alternator. However, this D+ switching signal is needed to recognise that the engine is running and to put various additional devices into function. On engines without an intelligent alternator, this works with a D+ simulator, as it detects the rising voltage of the starter battery and connects through. For vehicles with an intelligent alternator – mostly Euro 6 – this is only possible with a D+ active simulator. It is attached directly to the engine (cable set or similar) with cable ties and triggered by the engine vibration. When the engine stops, the signal switches off automatically. The delay is individually adjustable. Function is indicated via LED.