If a transformer reads OL between H1 to H2 on a multimeter after isolating the transformer, what does that indicate?

When a transformer shows an open loop (OL) reading between H1 and H2 on a multimeter, it indicates that there is an open circuit in the primary winding. This means there is no continuity in the circuit that would allow electrical current to flow through the primary winding. An open circuit typically occurs when there is a break in the wire or a failure in the winding itself, leading to a disconnection of the electrical path.

This condition suggests that the transformer is not operational, as it cannot receive power to convert and transfer to the secondary side. The reading correlates directly with a failure in the winding that prevents the necessary electrical function from occurring. In contrast, readings indicating a short in the winding would display a significantly lower resistance, and an operational transformer would show measurable resistance in its windings.