There Is A Power Outage; You Get A System Error - Carrier Comfort Touch-n-Go Owner's Manual

There is a power outage
If you lose electricity" and have batteries installed, the thermostat will continue to
display the status because it has a battery backup power source. This means that
even though your heating and cooling system doesn't work, you will still be able to
monitor your home's temperature. In addition, you won't have to reprogram the
thermostat because your settings are retained even if the battery dies. The display
will continue to show the time for 8 hours while there is no electricity.
You get a system error message
Here are the possible system error messages and what they mean:
-- The room air sensor reports that the room air temperature is above
150 ° or below - 50 °.
E4 This means the memory has failed and the thermostat will return to the
factory settings. Call your heating and cooling dealer.