My pump only has a knob that you can turn. It appears to be fully variable between low and high, but turning it in either direction doesn't make any difference. There doesn't appear to be any fixed settings. The label on the pump says: Type: ALPHA 15 - 60 130.
I have a Grundfos Alpha pump, about 8 year old, but it has developed a problem that I have seen registered on a number of sites including this one a couple of years ago, but I haven't seen anyone post the answer. I have the exact problem as quoted by mike from guilford in April 2008. In fact...