We got an above ground pool three years ago, and at the same time, the pump in question. It worked fine for the first two years, but now it will not turn on. A couple days ago, it had the same problem. I unplugged the extension cord it was attached to and left it alone. My mom went outside and it... started working just fine. Two days later I go out to replace the filter (Cartridge?), so I turn it off, open the thing, replace it, close the filter, go to turn it on, and... nothing's being filtered. I've tried loosening the screw thing on top of the cap to let out some pressure, as the manual says, but no dice. Tried changing the extension cord it was attached to, maybe it's the power source? Nothing changed. I'm not sure what the actual problem is, and I would be eternally grateful if anybody could help.