Before you start tapping on the pressure switch, open it and see if the points are closed. If they are not, then the nipple going to the switch is probably clogged. Could also be a bad switch. Cycling every 10-15 seconds is not a good thing. A pump needs to run for a minute and be off for a minute at a minimum. Either your tank is too small to use without a CSV or the tank is low on air and probably bad.