Primary water flow switches
Reasons a primary water flow switch will fail to start:
- Punctured / perished rubber diaphragm
- Seized bearing plate spindle / out of alignment
- Damaged / loose wiring harness
- Switch contact faulty
A demand for central heating will activate the pump and a rubber diaphragm / spindle arrangement communicates to a micro switch assembly above, transmitting a signal to the printed circuit board for correct operation.
To test a primary water flow switch (on a demand):
Pressure differential type:
Visually assess whether bearing plate spindle is rising through gland nut, activating the micro switch assembly above.
(No spindle movement may be due to a perished rubber diaphragm and/or seized bearing plate spindle).