If your home gets a little warmer than you want before the air conditioner cycles on, it could be that the temperature swing between the on and off cycle is too great. This is a common issue in the older mercury type thermostats. New digital thermostats are more accurate and have a smaller temperature swing, therefore maintaining a more constant temperature in the house. Old style thermostats turn on and off using a mercury switch inside. If you have a new heating and air conditioning system installed or have your thermostat replaced, make sure the contractor doing the job will be recycling the old thermostat and not just throwing it in the trash. Mercury will contaminate ground water. Mercury recycling is important to us at Jacob Heating & Air Conditioning.