how to test a transformer in circuit for short?

To test a transformer in-circuit for a short, first ensure the power is turned off and the circuit is de-energized. Use a multimeter to measure the resistance across the primary and secondary windings. A very low resistance reading (close to zero) indicates a short circuit within the transformer. Additionally, check for any unusual heating or burning smells, which can also indicate a short. If a short is suspected, further isolation and testing may be needed.