Adjusting a thermostat anticipator involves fine-tuning the lever arm in a particular way, depending on the symptoms that the furnace exhibits. When the heat anticipator is out of adjustment, it can cause the furnace to short cycle or make the temperature settings malfunction.
The first step is to locate the heat anticipator adjustment lever arm by removing the thermostat cover. The anticipator lever arm is fastened to a little disc at the center of the thermostat that has calibration marks, and depending on the make and model of the thermostat, has the word "longer" on it.
If the room temperature exceeds or falls short of the set temperature, move the heat anticipator lever arm away from the word longer or clockwise by one calibration mark. If the furnace cycle turns on and off too frequently, then move the anticipator lever arm anticlockwise or towards the word longer by one calibration mark.
After making the adjustment, allow the furnace to run and the temperature to stabilize for two or three hours, and repeat the same procedure at least once if there is no change. If the adjustment does not solve the issue and the problem persists, then consider replacing the thermostat.