True, but he can test it by putting a volt meter across the connector. He is just trying to verify if it is getting a signal to close (12V) when the CCU is set to cold. If the voltage is correct and the monovalve isn't closing, that's at least part of the problem. If the correct voltage is not getting to the valve, he needs to look elsewhere in the system. Also, if you plug and unplug it with the temp set to cold you can hear it click open and closed if it's working. Just a starting point.