[sunshine windows]

Give the filter before the pump ( if you have one  ) a good clean as I've found this has slowed my flow down considerably in the past.

[♠Winp®oClean♠]

Give the filter before the pump ( if you have one  ) a good clean as I've found this has slowed my flow down considerably in the past.

Yep, good call. A blocked strainer can restrict the flow to almost zero. I have assumed you mean the pump doesn't run unless it's switched to full? Or does it run but doesn't produce any flow unless it's on full?

[ants]

No, the problem is that  it just runs at full power all the time,no matter what setting its on.