If you're wondering why your central air conditioning unit is keeping your home too cold in the warmer months, it may be what's affecting your programmable thermostat. If you keep heat-producing items like lamps, electronics and appliances near your thermostat, it can throw off the entire air conditioning system. It will read your home as much warmer than it actually is and force the system to work harder. Be sure to place your thermostat away from heat-producing items and out of the sun's rays.