Domestic hot water and primary micro switches
Reasons a domestic hot water and primary micro switch will fail to start:
- Switch contact faulty
- Damaged / loose wiring harness
To test a domestic hot water and primary micro switch (on a demand):
- Electrically isolate boiler / system controls
- Set multimeter to continuity “buzzer” scale
- A continuity check of the wiring harness at the printed circuit board end will ascertain correct operation of switch and the integrity of wires also.
- No continuity present will be a complete new assembly (micro switch with wiring harness).
Continuity between C and NC = ok
Continuity between C and NO = faulty