We have an Ariston LS 609 Eco Care dishwasher. The soap dispenser will not ?

The soap Dispenser does not open during the wash. We have ordered a replacement part which has different electrical connections to the original. The replacement supplied was type 542 ( part number C00054930), which is supposed to fit, the original was type 540. We cannot find a wiring diagram to explain the difference in the connections. Can anyone help? Ariston was taken over by Indesit and then Hotpoint