What is a likely problem when a relay coil won't pull in?

When a relay coil won't pull in, one of the most common issues is an open coil. This occurs when the windings of the coil have been damaged or broken, interrupting the electrical path that is necessary for current to flow through the coil. As a result, when voltage is applied, the coil cannot generate the magnetic field needed to activate the relay.

In practice, this means that even if the relay is receiving voltage, the lack of continuity through the coil means it cannot perform its intended function. It's crucial to test the coil with a multimeter to determine whether it is complete and functioning correctly. If the coil is open, it will need to be replaced for the relay to operate properly.

The other factors listed may cause failure in relay operation, but they do not specifically indicate the relay coil itself has an open circuit, making the open coil the most direct and commonly encountered issue when a relay fails to pull in.