My ADV is either constantly free flowing or giving no flow at all.

Remove the Canister head and the flow cone. Check that the ADV tilt lever is still in place. Note. On Early units the tilt lever would on occasion come loose and drop out. The new unit has a modified tilt lever, which has eliminated this potential problem. If the tilt lever is not present remove the ADV assembly and replace the tilt lever with the new style tilt lever from VR Technologies.

Further Resources

Assembly & Testing Document

Video Link: ADV Removal
Video Link: ADV Replacement
Video Link: Head Stripdown