| The word HEAT or COOL is flashing in the thermostat display | This indicates that the heating or cooling system is currently running. When these systems are not running, HEAT or COOL will not flash |
| HEAT or COOL is flashing but the system is not running | The thermostat is telling the heating or cooling system to run, but the system is not responding. You may need to call your local heating and air conditioning contractor |
| Thermostat does not turn on heating or cooling system | Check to see if OFF is shown in display. This indicates that the system is turned off at the thermostat. Move the system selector switch to the HEAT or COOL position. After the compressor short cycle protection 5-minute period expires the system should start. |
| Compressor protection feature may be in effect due to compressor short cycle conditions. |
| Heating or cooling system may be malfunctioning. Call a professional service technician immediately to verify system operation |
| Thermostat turns on heating instead of cooling or cooling instead of heating | Check thermostat wiring to make sure that the heating and cooling stages are connected to the correct terminals on the wiring terminal block |
| Thermostat will not follow program set points | Check current time of day, day of week program settings. Make sure to verify AM/PM indicator is accurately displaying desired time settings. |
| Check to see if OFF is shown in display. This indicates that the system is turned off at the thermostat. Move the system selector switch to the HEAT or COOL position. After the compressor short cycle protection period expires the system should start within several seconds. |
| Verify your program set point time entries. The heating and cooling programs utilize the same set point times, but have individual set point temperatures for the MORN, DAY, EVE and NIGHT set points |
| Thermostat program has been temporarily overridden and program indicator is flashing in the display. Press the HOLD button twice to return the thermostat to normal program operation or wait until next set point and the temporary override will expire. |
| Thermostat program is in Extended Hold (Vacation) Mode and HOLD is showing in display. Press HOLD button to release permanent hold and return the thermostat to normal program operation |
| Thermostat turns heating or cooling system on too often or not often enough | : Increase or decrease first stage temperature differential setting as appropriate to provide the desired performance level |
| Low battery indicator is shown in thermostat display | Replace batteries immediately to maintain proper system operation |
| OFF is shown in thermostat display and heating or cooling system will not start | This indicates that the system is turned off at the thermostat. The thermostat must be in HEAT or COOL modes of operation to control the heating or cooling system. Move the system selector switch to the HEAT or COOL position |
| HI is shown in the thermostat display where the room temperature is normally displayed | The temperature sensed by the thermostat is higher than the 99˚ F (37˚ C) upper limit of the thermostat’s display range. The display will return to normal after the sensed temperature lowers within the 40˚ to 99˚ F (5˚ to 37˚ C) display range. Turn on the cooling system or use other methods to lower the temperature accordingly. This condition could occur from the system being turned off during an exceptionally warm period or upon installation when the thermostat has been stored for a long period of time in a warm vehicle or location prior to being installed |
| LO is shown in the thermostat display where the room temperature is normally displayed | The temperature sensed by the thermostat is lower than the 40˚ F (5˚ C) lower limit of the thermostat’s display range. The display will return to normal after the sensed temperature rises within the 40˚ to 99˚ F (5˚ to 37˚ C) display range. Turn on the heating system to raise the temperature as needed for comfort within the room. This condition could occur from the system being turned off during a cold weather period or upon installation when the thermostat has been stored for a long period of time in a cold vehicle or location prior to being installed. The thermostat should be allowed to warm up prior to installation to allow proper heating control once installed |
| Cannot program a set point temperature higher than 90˚ F (32˚ C) | This is above the normal thermostat temperature setting range of 45˚ to 90˚ F (7˚ to 32˚ C) |
| Cannot program a set point temperature lower than 45˚ F (7˚ C). | This is below the normal thermostat temperature setting range of 45˚ to 90˚ F (7˚ to 32˚ C) |
| Fan continues to run all the time whether the system is on or off | Check that the fan control switch is in the AUTO position. This will allow the fan to run only when the heating or cooling system is turned on and running. Check thermostat wiring to make sure that the fan control wiring is connected to the correct terminals on the wiring terminal block |
| The room is too warm or too cold | Verify the current set point and make any changes that are necessary |
| System turns on prior to the end of a setback period | Thermostat is in Adaptive Recovery Mode |
| NO AUX SET is shown in the thermostat display (model TT-P-421 only). | The thermostat (model TT-P-421 only) is configured for a conventional system, and the system switch is in the EM HEAT position. The unit will still function in a conventional 2 stage HEAT mode, but the display will flash NO AUX SET. Move the system switch to the HEAT position |
