Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the plastic cover from the hot water
microswitch and disconnect wires
microswitch and disconnect wires
Measurement:
With no demand for DHW measure the resistance across the hot water microswitch terminals.
Resistance should be open circuit.
Note:
Pulling the microswitch out of its housing may make this
test easier if the boiler is not in a convenient location.
Resistance should be open circuit.
Note:
Pulling the microswitch out of its housing may make this
test easier if the boiler is not in a convenient location.
Isolate as per TOPs P4
and refit as necessary