Thanks for the update,I haven't proceeded any further with this at present, busy with other things but did manage to get an "empty" reading of 140ish ohms when testing between the sender connection and earth but as you say,can't get the unit out to check "full" with the tank mounted in situ. The SAAS unit quotes 160 empty and 33 full as one of its pre-set options,apparently appropriate to a Honda setting so I may be able to go with this and adjust the float lever to give me a near enough, good enough solution as its really only the "empty" position that I am overly concerned with and as long as I get an idea of flow rate so that I know at which point I need to start being concerned,I think it may work. Anyway, think I will buy one, have a fiddle and see how I go.