Set Appliance State:
Mains Reset Switch OFF
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Remove Clip and remove diverter valve head from body
Disconnect electrical connector from H5 at the main PCB
Remove Clip and remove diverter valve head from body
Disconnect electrical connector from H5 at the main PCB
Measurement:
Test 1:
Measure resistances from bottom black wire to adjacent brown and blue wires.
Expect 8.5 kOhms or greater on both connections
Test 2:
Measure resistances from each of same black, brown and blue wires to a suitable earth point
Expect O.L or greater than 1 MOhm on all connections.
Note:
Take this opportunity to check for any signs of water ingress into valve actuator as this will also cause fuse to blow intermittently.
Measure resistances from bottom black wire to adjacent brown and blue wires.
Expect 8.5 kOhms or greater on both connections
Test 2:
Measure resistances from each of same black, brown and blue wires to a suitable earth point
Expect O.L or greater than 1 MOhm on all connections.
Note:
Take this opportunity to check for any signs of water ingress into valve actuator as this will also cause fuse to blow intermittently.
Isolate as per TOPs P4
and refit as necessary