What test can prove that a solenoid coil is open?

To determine if a solenoid coil is open, checking continuity with a digital multimeter (DMM) is the most effective method. This process involves connecting the probes of the DMM to the terminals of the solenoid. If the coil is functional and properly connected, the DMM will indicate continuity, showing a low resistance value. Conversely, if the coil is open, the DMM will display no continuity, indicating an infinite or very high resistance, hence confirming that the solenoid is not completing the electrical circuit.

While measuring the voltage across the solenoid can provide insights into its operational status, it won't definitively prove that the coil is open since the coil could still be functional and receive voltage without drawing current. Visual inspection may reveal obvious physical damage to the solenoid, but it may not detect internal faults or breaks, so it's not a reliable method for confirming an open coil. Testing the solenoid with a load can help determine if it's functioning while under power, but again, it won't specifically show whether the coil itself is open if the solenoid fails to operate under load. Thus, the best practice for confirming an open solenoid coil is to check continuity with a DMM.