Carrier PTACSTAT-NP-HP Installation & Operating Manual page 24

There are icons flashing on the thermostat display
There are several internal timers which influence the thermostat's operation. If a
timer is preventing the equipment from turning on, the display icons which show
the equipment is operating, will be flashing to indicate a turn- -on delay is present.
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_F or
below - -50_F.
E4 The memory has failed and the thermostat will return to the factory settings.
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