To adjust a thermostat that goes on and off too often or doesn't do a good job of controlling the room's temperature:
* Remove the thermostat's cover;
* Make sure mechanical thermostats with mercury switches (a little vial full of a silvery liquid) are level;
* Find the heat-anticipator°™often a small lever on a calibrated scale sometimes marked "longer";
* Adjust the heat-anticipator one mark closer to the "longer" setting if the furnace or air conditioning goes on and off too frequently;
* Move the lever away from the "longer" setting if you want the furnace or air conditioner to start up more often;
* Wait for the thermostat to stabilize at the new setting;
* Repeat if necessary; and
* If this doesn't work, replace the thermostat.
Turn off the power to the furnace, remove the old thermostat's cover, unscrew the low-voltage wires from the terminals and label them with tape according to their terminal designations. Remove the base plate from the wall.
Following the new thermostat's package directions, push the wires through the baseplate and screw it to the wall. Connect the terminals, then mount the cover.