Solenoid tank selector valve

[mybigtruck]

Got a 79 K 20 with dual tanks. The AUX tank has not been used in years. I am currently trying to see if it can be used. I get 12 volts to the connector that attaches to the valve, when the switch is set to the AUX tank position. When I connect it to the valve there is a slight clicking noise. This makes me think the valve is switching but I am not sure. How much noise should the valve make? Should it be an audible "Thunk" or just a little bit of a click like I am hearing? Any suggestions for a test to be certain if the valve has switched? All I can think of is to get the truck running and switch to the AUX tank. If it switches then the engine should continue to run and, of course, it will die if it does not switch. Anyone have any better ideas than this?

THX for any and all help.