Hello guys,I'm new here and want to pick your expert brains. I've refurbed my old Vokera 80SP's hydraulics (diaphragms etc) but when I was pressurising the system the pressure gauge never lifted off zero.I bled all the radiators and gave it one last gentle skoosh to see if it would do the trick but no. All I succeeded in doing was to blow the PRV. I drained the system down and removed the pressure gauge prior to ordering a new one. I cleaned off the sender end and blew into it. To my surprise the needle kicked a bit.So if I can make it move with lung power has it really failed? What does the sender probe actually contact in the manifold? Is it water as I can only see some sort of gray/white material when I look in with a torch.As I say I've got a new gauge coming but I'm wondering if that's going to fix things.