Domestic hot water and primary micro switches

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

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