It'll click on and off every few seconds during normal operation. You can warm the engine and set the climate control to heat, say 80 degrees, and it should turn on and off every 3-5 seconds or so. If it doesn't come on at all, turn the heat all the way up. If that doesn't cause the voltage to cycle, then the climate control head is not operating properly.
In a properly operating momovalve, you can just put your finger on the top of the plunger and feel it click every few seconds.

DG