Set Appliance State:

Mains Reset Switch OFF
Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove Clip and remove diverter valve head from body
Disconnect electrical connector from valve actuator

Measurement:

At exposed connectors Measure resistances from central connection to each of the outer connections.
Expect 8.5 kOhms or greater on both 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.