Replacement micro switch for the Grid Controls M310 liquid flow switch.
Troubleshooting your M310:
Before you decide to replace your micro switch test it by de-energising the circuit then depress the small switch located on the opposite side of the common contact. Use a multimeter to measure a change in continuity between the common contact and the NC and NO contacts. See images for diagram.
If your contacts work correctly the problem is most like in the flow body caused by slime, dirt or debris. De-presurize your water system, turn off any pumps before opening up the M310 flow body. Carefully clean it out using a soft rag and mild soap and water. Re-install magnetic float and test the system. Avoid adjusting the factory set setscrew or you will throw the flow switch out of calibration. The M310 should activate at 1 gallon per minute of water flow and should always be installed horizontally to allow gravity to help the float drop down into the flow body.
Typical Wiring Schematic: