A thick film circuit on an insulating substrate includes a thermal fuse. The circuit includes a conductive strip, which may be sufficiently resistive to comprise the resistor of an automotive fan motor controller, which is made of a material dissolved by a solder which melts at a predetermined temperature. When an abnormal event occurs which raises the temperature of the circuit, the solder melts and dissolves the underlying conductive strip. The solder and melted material of the strip then coalesce into one or more droplets thereby breaking the circuit.