Technician A says that the current flow through a rear-window defogger can be often self-regulating. Technician B says that as the temperature of the grid decreases, its resistance decreases, reducing current flow. Which technician is correct

Technician A is correct

Explanation:

Technician B is wrong because decrease in resistance will surely cause increase in the flow of current.

As temperature rises, the number of phonons increases and with it the likelihood that the electrons and phonons will collide. Thus when temperature goes up, resistance 

goes up. For some materials, resistivity is a linear function of temperature. The resistivity of a conductor increases with temperature.