A printhead IC is provided which has an array of nozzles, drive circuitry for receiving print data and sending drive pulses of electrical energy to the array of nozzles in accordance with the print data, a temperature sensor connected to the drive circuitry to adjust the drive pulse profile in response to the temperature sensor output and open actuator test circuitry for selectively disabling the actuators when they receive a drive signal while comparing the resistance of the resistive heater to a predetermined threshold to assess whether the actuator is defective. During use, the temperature sensor can be de-activated after a period of use.