Diplomat ADP 8322

The dishwasher ran but the plates were not clean.
Opening the door during a cycle revealed the spray arms were not going around.
‘Fiddling with the door’ to make the cycle continue showed the water pressure is too low to make arms spin, though they are NOT blocked ie 6inch ‘fountain’ from lower arms only when in place – but if that is removed, & ‘hole’ blocked, then a small spray from top arms.
I assumed a pump was required to increase water pressure but apparently drain pump is the only pump in the d/w. Is the ‘pressure switch’ the problem ?
Help please …..have read lots of other threads with this model ….is there any way to search by model no. & not wade through 40+ pages ?
As this is a ‘Whirlpool’ model – could you advise number so I can locate Technical Manual – MFI/Howdens have no technical help by phone!