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Troubleshooting
Stuck? Let our troubleshooting guides help you
These troubleshooting guides will help you with any setup and installation questions you may have:
No Heat/No Cool/No Fan (common problems)
No Heat
No Cooling
No Heat or No Cool
Heat, Cool, or Fan Runs Constantly
Blank Display and/or Keypad Not Responding
Furnace (air conditioner) cycles too fast or too slow (narrow or wide temperature swing)
iThermostat™ Setting & iThermostat Thermometer Disagree
Heat Setpoint will not Respond to the Temperature Up Key
Cool Setpoint will not Respond to the Temperature Down Key
Forgot Keypad Lockout Code
No Heat/No Cool/No Fan (common problems)
Possible Cause:
- Blown fuse or tripped circuit breaker.
- Furnace power switch is OFF.
- iThermostat switch in wrong position
- Furnace blower compartment door or panel loose or not properly installed.
Corrective Action:
- Replace fuse or reset breaker.
- Turn switch to ON.
- Make sure RC/PS switch in the proper position. If there is a wire attached to the C terminal of the iThermostat, the switch should be in the RC position. If there is no wire on the C terminal, the switch should be in the PS position.
- Replace door panel in proper position to engage safety interlock or door switch.
- Re-light pilot
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No heat
Possible Cause:
- Pilot light not lit.
- System Switch not set to HEAT.
- Loose connection to iThermostat or system.
- Furnace Lock-Out Condition. Heat may also be intermittent.
- Heating system requires service or iThermostat requires replacement.
Corrective Action:
- Press SYSTEM button to select HEAT and press
 to raise the temperature setpoint above room temperature.
- Verify iThermostat and system wires are securely attached.
- Many furnaces have safety devices that shut down when a lock-out condition occurs. If the heat works intermittently contact the furnace manufacturer or local service person for assistance.
Diagnostic
Press SYSTEM button to select HEAT and press to raise the temperature setpoint above room temperature. Within a few seconds the iThermostat should make a soft click sound. This sound usually indicates the iThermostat is operating properly. If the thermostat does not click, try the reset operation as detailed in the Installation Manual. If the iThermostat does not click after being reset, contact your heating and cooling service person or the TXU Energy Conservation Program at 1-866-733-1807. If the thermostat clicks, contact the furnace manufacturer or a service person to verify the heating is operating correctly.
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No Cooling
Possible Cause:
- System Switch not set to COOL.
- Loose connection to iThermostat or system.
- Cooling system requires service or iThermostat requires replacement.
Corrective Action:
- Press SYSTEM button to select COOL and press
 to lower the temperature setpoint below room temperature.
Verify iThermostat and system wires are securely attached.
Diagnostic
Press SYSTEM button to select COOL and press to lower the temperature setpoint below room temperature. Within a few seconds the iThermostat should make a soft click sound. This sound usually indicates the iThermostat is operating properly. If the thermostat does not click, try the reset operation as detailed in the Installation Manual. If the iThermostat does not click after being reset, contact your heating and cooling service person or the TXU Energy Conservation Program at 1-866-733-1807. If the thermostat clicks, contact the furnace manufacturer or a service person to verify the cooling is operating correctly.
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No Heat or No Cool
Possible Cause:
- iThermostat may be in a cycling event. The word SAVE will appear on the display and the green LED will be illuminated.
Corrective Action:
- Wait for cycling event to end.
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Heat, Cool, or Fan Runs Constantly
Possible Cause:
- FAN switch set to Fan ON.
- Possible short in wiring, iThermostat, or HVAC system
- Possible need of common, 5th wire
Corrective Action:
- Change FAN switch to AUTO.
- Check each wire connection to verify they are not shorted or touching together. No bare wire should stick out from under terminal screws. Try resetting the iThermostat as detailed in the Installation Manual. If the condition persists, contact a service person to add a 5th wire or replace the iThermostat.
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Blank Display and/or Keypad Not Responding
Possible Cause:
- iThermostat switch in wrong position
- Voltage spike or static discharge.
Corrective Action:
- Make sure RC/PS switch in the proper position. If there is a wire attached to the C terminal of the iThermostat, the switch should be in the RC position. If there is no wire on the C terminal, the switch should be in the PS position.
- Use the Reset Operation described in the Installation Manual.
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Furnace (air conditioner) cycles too fast or too slow (narrow or wide temperature swing)
Possible Cause:
- The location of the iThermostat and/or the size of the Heating System may be influencing the cycle rate.
Corrective Action:
- Digital thermostats normally provide precise temperature control and may cycle faster than some older mechanical models. A faster cycle rate means the unit turns on and off more frequently but runs for a shorter time so there is no increase in energy use. If you would like to increase the cycle time, choose SL for slow cycle in the configuration menu, step 4 (see User's Manual). If an acceptable cycle rate is not achieved as received or by choosing slow cycle, contact a local service person for additional suggestions.
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iThermostat Setting & iThermostat Thermometer Disagree
Possible Cause:
- iThermostat thermometer setting requires adjustment.
Corrective Action:
- The thermometer can be adjusted +/- 3 degrees. See Temperature Display Adjustment in the Configuration Menu section of the User’s Manual.
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Heat Setpoint will not Respond to the Temperature Up Key
Possible Cause:
- The desired setpoint conflicts with the setpoint of the COOL mode.
Corrective Action:
- Change system mode to COOL. Raise the Cool setpoint. Return to HEAT mode and set desired temperature.
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Cool Setpoint will not Respond to the Temperature Down Key
Possible Cause:
- The desired setpoint conflicts with the setpoint of the HEAT mode.
Corrective Action:
- Change system mode to HEAT. Lower the Heat setpoint. Return to COOL mode and set desired temperature.
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Forgot Keypad Lockout Code
Possible Cause:
- Forgot keypad lockout code.
Corrective Action:
- Press the up arrow, down arrow, and SYSTEM buttons at the same time to reset the lockout code, unlock the keypad.
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