Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove diverter valve head from body
Measurement:
Observe the position of the spindle.
If the spindle is extended (Heating Position) expect approximately 6Kohms between Pins 2 and 3.
If the spindle is retracted (Hot Water Position) expect approximately 6Kohms between Pins 1 and 2.
The spindle may be not be fully in one position so also test for 6Kohm between Pins 1 and 2 / Pins 2 and 3, and for continuity between Pins 1 and 3 .
Note:
It is also advisable to check for any water
leaks from the diverter valve body as this can
also cause the fuse to blow and may be intermittent.
If the spindle is extended (Heating Position) expect approximately 6Kohms between Pins 2 and 3.
If the spindle is retracted (Hot Water Position) expect approximately 6Kohms between Pins 1 and 2.
The spindle may be not be fully in one position so also test for 6Kohm between Pins 1 and 2 / Pins 2 and 3, and for continuity between Pins 1 and 3 .
Note:
It is also advisable to check for any water
leaks from the diverter valve body as this can
also cause the fuse to blow and may be intermittent.
Isolate as per TOPs P4
and refit as necessary