A heater control system for a gas delivery system of a substrate processing system includes an oven, N resistive uninsulated heaters arranged inside of the oven, where N is an integer greater than one, and a controller. The oven encloses one or more components of the substrate processing system and to maintain a predetermined temperature in the oven. Each of the N resistive heaters selectively heats at least a portion of one of the components in the oven. The controller is configured to maintain the predetermined temperature in localized regions in the oven by determining a resistance in each of the N resistive heaters and adjusting power to each of the N resistive heaters based on N-1 resistance ratios of N-1 of the N resistive heaters relative to one of the N resistive heaters.