all the relay does is provide power to the pump, if the drivers door has been opened, then it gets some current and the relay powers up the pump, it will only go off when the ignition is cut.
The pump only runs when it is told to by the ECU. This is determined by a pressure sensor, so if your pump isconstantly running, I would suspect the accumulator (why helps maintain the pressure) and the spherical shaped object on the acctuator, or the pressure switch.
The accuator is not available from Alfa but is from Fiat, the pressue switch, bag one off ebay, plenty of seles being broken.
I may be talking crap of course, a diagnostic will help pinpoint the problem or Alfa Diag and a cable from Rarebear, but that is where I would look if it were me.
I guess you have access to some diagnostic as you mention the fault 'being cleared'.