Abstract: In a gas chromatography system of the type including an oven for the GC column, and an electric heater for controllably heating the oven; an improved system is disclosed for controllably opening and closing the oven door to enable a fully controlled heat leak, thereby to stabilize the oven temperature at a desired set point. A signal indicative by first or second conditions of an oven temperature above or below the set point is generated. A heater power control responds to one of the signal conditions by effecting heating of the oven. Bi-directional door motor and actuator means are provided for opening and closing the oven door over a prescribed operating range, and these means are enabled to operate for a predetermined period upon the signal in its first or second condition departing from preset threshold values for a predetermined period whereby closing or opening of the oven door is effected in incremental steps.