Zanussi ZWF1631W Noisy Module

I wondered if this is normal or does it indicate something about to blow? When you first switch on the module makes a noise similar to a fridge compressor only quieter. It then goes into an alarm mode and displays E30 and the pump operates. Sometimes if you press the skip/reset button it resets the system and the machine will operate OK for 2 or 3 washes. Customer says it sometimes displays E34, which is a disagreement between the 2 pressure switches. I think the module makes this noise all the time but it is mostly drowned out by the other sounds.