It is really difficult to determine whether a winding is shorted using an ordinary multimeter or DVM because the DC resistance of most transformer windings is below the range that most instruments can accurately measure. A shorted turn that can lead to destructive heating within the winding may reduce the resistance of the winding by less than the resolution of the ohmmeter. And if you did not have a precise measurement of the winding resistance before the suspected failure, what are you going to compare your present measured value to?
Depending upon the rating of your transformer, you may be measuring mostly the resistance of your clip leads. I just measured the resistance of the 115 volt primary of a 150 watt transformer to be 2.955 ohms. This was using a 4-wire "Kelvin Connection" that eliminates the influence of clip lead resistance. The same measurement using a standard 2-lead connection with the same instrument indicated 6 or 7 ohms with the reading fluctuating too much over time to get a reasonable reading.
A possibly better way of determining whether a winding is shorted might be to resonate a winding of the suspect transformer with a shunt capacitor and observe the ringing waveform on an oscilloscope after pulsing the parallel LC circuit with a DC source. Very rapid decay with only one or two cycles visible on the oscilloscope would indicate that a shorted turn is absorbing energy from the LC circuit. Ringing sustained for a dozen or more cycles would indicate no shorted turn. These values are pure guesses and should be confirmed with a known good transformer of similar power rating to the suspect transformer if you try the technique. Actually the capacitor can be paralleled with any winding and any winding can be pulsed because the effect of the shorted turn is transformed to all windings.
How did you perform the measurement of the winding resistance and what was your observation?
awright