In the measurement using a hot soldering iron near the resistance, then resistance should be significantly increased

Fuse resistor resistance generally only a few to tens of Europe, if the measured resistance is infinite, they have been blown. Also available online to detect fuse resistance is good or bad, were measured at both ends to ground voltage, if one end of the supply voltage, end voltage of 0 volts, the fuse has blown resistance.
More types of sensitive power transformers to the thermal resistor, for example, and of a positive temperature coefficient and a negative temperature coefficient thermistor. For a positive temperature coefficient (PTC) thermistor mcb circuit breaker at room temperature, generally small, the measurement using a hot soldering iron near the resistance, then the resistance should be significantly increased, indicating that the resistance is normal, without changes show component damage, the negative temperature coefficient thermistor opposite.