Paul --

The "frequency valve" buzzes 'n clicks 'n chatters during normal operation. First, with the engine idling, listen or feel to valve to confirm that it's speaking to you. Second, while idling, unplug connector at the relay and see if the engine changes idle (probably drop and become rough).

If yes, then you've disabled a functioning system. If no, then be suspicious that it's not working.

Also, pull the connector at the valve. 'Though difficult to see in the pix, you'll see on your car that it faces upwards and can hold water. If water's present it'll dissolve the internal connectors over time (because of electrolytic action).

While you have the connector off the relay, inspect the connectors -- looking for corrosion, oxidation, or signs of bad connections. Clean 'em all up -- if nothing else, as a preventative measure.