Freezing temperatures and non-circulating swimming pools is a bad combination. One of the most common problems found with freeze guards is that the thermostat is not registering the freezing temps or that the thermostat is registering incorrectly. Either way if it is below freezing and your pump is not running, costly freeze damage is likely to occur. Note that it is common for the freeze guard to register about a 5-degree difference from the outside temperature. This is why the freeze guard should be set to 38 to compensate. If set properly and you have to set the thermostat 10 degrees higher just to turn the pump on, it might be time to replace the thermostat. The good news is it is generally an easy replacement that the average handy home owner can do.