Lennox Thermostats Troubleshooting

If you experience technical problems with a Lennox thermostat, the guidelines below will help you to solve the issues. Each manual is present in the form of a manual and mentions the most widespread technical failures and problems. Identify the problem and its causes, and fix the device – the tables cover the entire range of issues that can be eliminated manually, or with WiFi connection.

Lennox T7300 Thermostats Troubleshooting

SymptomPossible CauseAction
Display does not come on.Thermostat is not being powered.Check for 24 Vac between C and Rc.
Check that AAA batteries are installed correctly and are good.
Temperature settings do not change.The upper or lower tempera- ture limits were reached.Check temperature setpoints.
Check Installer Setup Numbers 0600 and 0610; modify as needed.
The keypad is fully locked.Check Installer Setup Number 0670 to change keypad locked options.
Heating or cooling does not come on.Thermostat minimum off- time is activated.Wait up to five minutes for the system to respond.
System selection not set to Heat or Cool.Set system Selection to correct position.
System type Selection is incorrect.Check Installer Setup Number 0170 and make sure correct System type is chosen.
Thermostat is calling for Heat (Heat on) or Cool (Cool on) but no heating or cooling is running.Heating or cooling equipment is not operating.Check wiring.
Check Installer Setup Number 0170 and make sure correct system type is chosen.
Verify operation of equipment in System Test mode.
Heat does not turn on (Heat On is solid in the display).Heating equipment failure.Check for 24Vac at the equipment on the secondary side of the transformer between power and common. If voltage is not present, check the heating equipment to find the cause of the problem.
Check for 24 Vac between the heat terminal (W) and transformer common. If 24 Vac is present, the thermostat is functional. Check the heating equipment to find the cause of the problem.
Loose or broken wire connection between thermostat and heating equipment.Check for 24 Vac between the heat terminal (W) and transformer common. If voltage is not present, check wire connection (loose or broken) between the thermostat and the heating equipment.
Both the heating and coding equipment are running at the same time.The heating equipment is not a heat pump but the System Type (Installer Set- up Number 0170) is set to Heat Pump.Set System Type (Installer Setup Number 0170) to match the installed heating and/or cooling equipment
Heating and cooling wires are shorted together.Separate the shorted heating and cooling wires.

Lennox Commercial Touchscreen Thermostats Troubleshooting

Problem Cause / Solution
Some or all keys on the display do not work; why not?Thermostat screen is locked
Backlighting seems dim; is it designed to be dim?When using batteries for power, install fresh AAA alkaline batteries
Thermostat is asking for heating or cooling to come on (screen shows -Heat On- or -Cool On- in display) but there is no heating or cooling running.Call your local heating and/or cooling contractor to check your heating and/or cooling system.
Why doesn’t the thermostat respond when 1 touch the screen?Check to determine if the screen is in the Locked or Clean mode.
The thermostat only allows selection of one day to program. Why is this?Check the screen to ensure it shows OK TO PICK MULTIPLE DAYS. You may need to simply press EDIT.

Lennox Merit Series Thermostats Troubleshooting

SYMPTOMPOSSIBLE CAUSESCORRECTIVE ACTION
1. Spark igniter will not light pilot after repeated triggering of igniter button.A. Defective igniter (no spark at electrode).Check for spark at electrode and pilot; if no spark and electrode wire is properly connected, replace igniter.
B. Defective or misaligned electrode at pilot (spark at electrode).Using a match, light pilot. If pilot lights, turn off pilot and trigger the igniter button again. If pilot lights, an improper gas mixture caused the bad lighting and a longer purge period is recommended. If pilot will not light - check gap at electrode and pilot - should be 1/8' to have a strong spark. If gap does not measure 1/8", replace pilot
C. Gas supply pressure errant.Check inlet gas pressure. Itshould be within the limits as marked on the rating plate.
D. Pilot orifice plugged.Clean or replace pilot orifice.
2. Pilot will not stay lit after carefully following the lighting instructions.A. Defective pilot generator (thermocouple).Check pilot flame, it must impinge on thermocouple. Clean and/or adjust pilot for maximum flame impingement on thermocouple. Ensure that the connection between the valve and thermocouple are tight and secure.
3. Pilot burning, no gas to burner, Valve knob “ON,” and the (standard) burner OFF/ON switch is “ON." Read important note below.A. Wall switch or wires defective.Check wall switch and wires for proper connections. Jumper wire across terminals at wall switch, if burner comes on, replace defective wall switch. If okay, jumper wires across wall switch wires at valve, if burner comes on, wires are faulty or connections are bad.
B. Thermopile may not be generating sufficient millivolts.Check thermopile with millivolt meter. Take reading at thermopile terminals of gas valve. Should read 325 millivolts minimum with optional wall switch “OFF.” Replace faulty thermopile if reading is below specified minimum.
C. Plugged burner orifice.Check burner orifice for blockage and remove.
D. OFF/ON Switch and 'Remote Switch are in the "ON" position resulting in excessive resistance.When turning on the burner using a 'remote switch, ensure that the standard OFF/ON switch is in the "OFF" position. If both switches are in the ON position, it may result in excessive resistance (and millivolt drainage) and the burner may not come on.
4. Frequent pilot/burner outage problem.A. Pilot flame may be too low or blowing (high) causing the pilot/valve safety to drop out.Clean and/or adjust pilot flame for maximum flame impingement on thermocouple

Lennox 11U61 Thermostats Troubleshooting

Problem Cause / Solution
ROUTER / MODEM CONNECTION FAILSMake sure the router and modem are turned on.
Check for connections to other wireless devices and internet connection.
Make sure the thermostat's Wi-Fi is enabled and connected to the home network (Router).
If having difficulty connecting to the router, online research the router model number and/or internet provider to discover and verify that the router band is set to B, G or N bands. You will need to access the routers utility program to make any changes. If not accessible please contact your service provider for help. The thermostat will connect to B, G or N band routers at this time.
NOTE: When set to B or G bands, video streaming will likely be slower that N band. If homeowner has implemented a dedicated N band router for the purpose of video streaming, a separate router for the thermostat may be required.
Reboot your router

Lennox Icomfort Wi-Fi Thermostats Troubleshooting

Alert CodePriorityAlert TextSteps to clear
10Critical(Stat) The thermostat has found an unknown device on the system.An unknown device is seen on the subnet in or outside of configuration mode. Clear by reconfiguring the system. Press the setup tab, press start, and press confirm. If problem persists, then check all DEVICE connections to make sure they are icomfortcompatible.
11Critical(Stat) The thermostat cannot find a previously installed unit.Check all connections and cycle system power. If problem persists, clear by reconfiguring the sys- tem. Press the setup tab, press start, and press confirm. If problem persists, then check all DEVICE connections to make sure they are icomfort-compatible.
12Critical(Stat) The thermostat cannot find an icomfort- enabled indoor unit.Thermostat did not find an Indoor Unit. Make sure there is an icomfort indoor unit on the system. Check R, i+, i- and C connections, ohm wires and cycle power. Replace indoor unit control board if there is no response.
14Critical(Stat) The thermostat found more than one ther- mostat, more than one indoor unit, or more than one outdoor unit on the system.Check wiring and remove duplicate equipment. Reconfigure system.
18Minor(Stat) The outside temperature is below the lev- el where the heat pump is programmed to heat the home. The system will not use the heat pump to warm your home.Notification only - Outdoor Temp is below the Low Balance Point. Heat Pump will not be used to service a heating demand.
19Minor(Stat) The outside temperature is higher than the level where the furnace or electric heat is programmed to work. The system will only use the heat pump to warm your home.Notification only - Outdoor Temp is above the High Balance Point. Indoor Unit (furnace or air-handier) will not be used to service a heating demand.
29Critical(Stat) The thermostat is reading an indoor tem- perature that is higher than 99°F. The thermo- stat will not allow any heating operation to begin until it senses a temperature lower than 99°F.Indoor temperature rose above 99°F during a heating or cooling demand. Heating operation is not allowed. Check to ensure that Heating Equipment is not stuck ON (reversing valve, etc.). Check the accuracy of the thermostat temperature sensor. Select cooling system mode to cool the indoor space.
30Moderate(Stat) The thermostat is reading an indoor tem- perature that is lower than 40°F. The thermostat will not allow any cooling operation to begin un- til it senses a temperature higher than 40°F.Indoor Temp fell below 40°F. Cooling operation is not allowed. Check to ensure that cooling equipment is not stuck ON. Check accuracy of the thermostat temperature sensor. Select heating system mode to heat the indoor space to above 40°F.
31Critical(Stat) The thermostat has lost communication with the (furnace, air-handier or outdoor unit) for more than 3 minutes.[Indicated unif\ has not communicated with thermostat for more than 3 minutes. Check connections. Ohm wires. If fault persists, then cycle power. Fault clears after communication is restored.
32Moderate(Stat) The (furnace, air-handier or outdoor unit) is resetting itself.[Indicated unif\ is resetting itself. This event may occur during a power outage or power fluctuation in the system. If persistent or if it coincides with the system operation then proceed with the following steps. Check the power connections, check the amp draw at the transformer (the transformer maybe overloaded) and check 24VAC voltage at the DEVICE. The alarm is only cleared by pressing the clear button on the Installer Alerts Tab. If the fault persists after checking the connections, replace the unit's control board.
34Critical(Stat) The thermostat does not know the capac- ity (tonnage) of the (furnace, air-handier or out- door unit). Please program the correct capacity of the (furnace, air-handier or outdoor unit).[Indicated unif\ is missing the programmed unit capacity. Go to [Indicated unif\ and program the unit capacity manually. Remove power to thermostat before programming the unit control board. Once programming is complete, reconnect thermostat wires and reconfigure system.
36Critical(Stat) The system has been heating for at least 15 minutes, without a demand for heating.Run the system in diagnostic mode and verify that it matches actual equipment operation. Check for other alarms/codes that may be preventing the system from operating as expected.
Step 1: Check all heating equipment to determine cause of heating demand.
Step 2: Recycle power.
System will clear code when it detects condition has cleared.
37Critical(Stat) The system has been cooling for at least 15 minutes, without a demand for cooling.Run the system in diagnostic mode and verify that it matches actual equipment operation. Check for other alarms/codes that may be preventing the system from operating as expected.
Step 1: Check all cooling equipment to determine cause of cooling demand.
Step 2: Recycle power.
System will clear code when it detects condition has cleared.
38Critical(Stat) The system has not been able to turn on the heating tor more than 45 minutes. The sys- tem will go offline for 60 minutes and try again.Run the system in diagnostic mode and verify that it matches actual equipment operation. Check for other alarms/codes that may be preventing the system from operating as expected.
Step 1: Check all heating equipment to determine cause.
Step 2: Recycle power.
System will clear code when it detects condition has cleared.
39Critical(Stat) The system has not been able to turn on the cooling for more than 45 minutes. The sys- tem will go offline for 60 minutes and try again.Run the system in diagnostic mode and verify that it matches actual equipment operation. Check for other alarms/codes that may be preventing the system from operating as expected.
Step 1: Check all cooling equipment to determine cause.
Step 2: Recycle power.
System will clear code when it detects condition has cleared.
105Critical(Stat / Furnace / Air Handler / Outdoor Unit) The (stat, furnace, air-handier or outdoor unit) has lost communication with the rest of the system.Equipment is unable to communicate. This may indicate the existence of other alarms/codes. In most cases errors are related to electrical noise. Make sure high voltage power is separated from RSBus. Check for miswired and/or loose connections between the stat, indoor unit and outdoor unit. Check for a high voltage source of noise close to the system. Generally, this is a self-recoverable error.
110Critical(Furnace) The line voltage is too low.This alarm/code may appear during a brownout. Line voltage is below its designed operating value. Check and correct tne power line voltage.
111Critical(Furnace) The line power voltage wiring is re- versed.The unit is reporting that its power line and neutral are reversed. Turn off the power to the system and correct the line power voltage wiring. System resumes normal operation 5 seconds after fault recovered.
112Critical(Furnace) The reporting device cannot find earth ground. The thermostat will shut down the system.Provide proper earth ground to the equipment. System resumes normal operation 5 seconds after fault recovered.
113Critical(Furnace) The line voltage is too high.Line voltage high (voltage higher than nameplate rating). Provide power voltage within proper range. System resumes normal operation 5 seconds after fault recovered.
114Critical(Furnace / Air Handler) There is a frequency/ distortion problem with the power to the (furnace or air-handier).This alarm/code may indicate transformer overloading. Check the voltage and line power frequency. Check the generator operating frequency, if the system is running on back-up power. Correct voltage and frequency problems. System resumes normal operation 5 seconds after fault recovered.
115Critical(Furnace / Air Handler) The 24VAC to the (fur- nace or air-handier control board) is lower than the required range of 18 to 30VAC.24-Volt Power Low (Range is 18 to 30 volts). Check and correct voltage. Check for additional power- robbing equipment connected to system. This alarm/code may require the installation of an addition- al or larger VA transformer.
117Minor(Furnace) The reporting unit has poor earth grounding.Provide proper grounding for the unit. Check for proper earth ground to the system. The alarm/code will clear 30 seconds after it is corrected.
120Moderate(Stat / Furnace / Air Handler / Outdoor Unit) There is a delay in the (stat, furnace, air-handier or outdoor unit) responding to the system.Typically, this alarm/code does not cause any issues and will clear on its own. The alarm/code is usually caused by a delay in the outdoor unit responding to the thermostat. Check all wiring connections. Cleared after unresponsive device responds to any inquiry.
124Critical(Stat / Furnace / Air Handler / Outdoor Unit) The thermostat has lost communication with the (fur- nace, air-handier or outdoor unit) for more than 3 minutes.Equipment lost communication with the thermostat. Check the wiring connections, ohm wires and cycle power. The alarm stops all associated HVAC operations and waits for a heartbeat message from the unit that's not communicating. The alarm/fault clears after communication is re-established.
125Critical(Stat / Furnace / Outdoor Unit) There is a hard- ware problem on either the (stat, furnace control board, air-handier control board or outdoor unit control board).There is a control hardware problem. Replace the control if the problem prevents operation and is persistent. The alarm/fault is cleared 300 seconds after the fault recovers.
126Critical(Furnace / Outdoor Unit) There is an internal communication problem with the (furnace con- trol board, air-handier control board or outdoor unit control board).There is an internal hardware problem on the control. Typically the control will re-set itself. Replace the control if the problem prevents operation and is persistent. The alarm/fault is cleared 300 seconds after the fault recovers.
130Moderate(Air Handler) An air-handier configuration jump- er is missing.Configuration jumpers) missing on control (applicable in non-communicating applications only). Replace the jumper or put wire between terminals on control. Cleared after jumper is connected.
131Critical(Stat / Furnace / Air Handler / Outdoor Unit) The (stat, furnace, air-handier or outdoor unit) con- trol parameters are corrupted.Reconfigure the system. Replace the control if heating or cooling is not available.
132Critical(Air Handler) The air handler control software is corrupted.Recycle power. If failure re-occurs, replace the control. System reset is required to recover.

Lennox XP1906 Thermostats Troubleshooting

Issue / ProblemPossible CauseCorrective Action / Comments
- No electric heat operation.Electric heat was not manually configured configured at the Air Handler Control (AHC) before the icomfort Wi-Fi ™ system discovery process at initial power-up.- Manually configure to discover the electric heat section(s) on the air handling
- The thermostat system setting does not offer a emerg. heat choice on an HP system.- Re-setup the icomfort system by selecting the setup button in the Installer program and press start to begin system discovery; then reconfigure the system.
Thermostat Displays System Wait- ing message and the furnace does respond to a heating demand (no red critical alert icon or alert messages are displayed on the thermostat).The furnace is in “watchguard” mode (moderate alert) and will not display the red critical alert icon nor be displayed in the homeowner alert button.- Go to the installer program alert button to view all alerts and details about those alerts.
- If the furnace is in “watchguard” mode, the furnace can be reset from the Home screen by setting the thermostat system settings to off for 20 sec, then back to heat. Then initiate a new heat demand.
Outdoor temperature is not displayed on the thermostat.Outdoor Temp Display must be enabled to display the outdoor temperature on the home screen.On the home screen, press the right arrow Q3 then press the display settings button. Click on outdoor temp dis- play button to toggle ON.
A humidifier was added to the system as non-communicating equipment and the thermostat does not provide the ability to adjust the RH setpoint.Humidification Control Mode is- In the installer program, select the equipment button. Select “Sys- tem" from the device list using the up/down arrows and press the edit button. Use up/down arrows to select Humidification Control Mode from the list. Select the desired humidifier control mode: Basic, Preci- sion, or Dew Point. (Basic is the most popular) and press the save button. Follow the red instructions then exit the system.
set for “Display only 1 ’ which will not allow the icomfort system to control the humidifier.- If Humidification Control Mode is not offered as a menu item choice, the Humidifier must be added to the icomfort system using the Add or Remove Non-communicating equipment screen under the thermostat installer program in the setup button.
The non-communicating outdoor unit is part of the system, but the thermo- stat does not display the outdoor unit.The outdoor unit was not added as a non-communicating unit during initial system setup.In the thermostat installer program select the setup button and follow the on screen instructions until you reach the Add or Remove Non- communicating equipment screen; press yes. Select Outdoor Unit Type from the menu and press the edit button. Select 1 Stage AC Unit or 2 Stage AC Unit and press save. Follow the red instructions then exit the system.
High Balance Point and Low Balance Point are not listed as a menu item to adjust the setpoint on the thermostat of the heat pump system.Balance Point Control must be enabled to display as the High Balance Point and Low Balance Point in the menu and pro- vide the ability for the installer to adjust the setpoint.- In the installer program select the equipment button, then scroll down to system device to System and press edit. Scroll down the menu item choices to Balance Point Control and press edit. Select enable and press save. High Balance Point and Low Balance Point are now listed; adjust the balance point settings and press save.
- If Balance Point Control is not shown as a menu item choice, the system is not connected to Wi-Fi or does not have/recognize an outdoor sensor or the system is not a heat pump.
icomfort thermostat does not show a choice for Dew Point Control Hu- midification mode (only Basic and Precision choices).Dew Point Control will only be displayed if the system has an outdoor sensor.- Add an outdoor sensor to the system and connect to the outdoor sensor terminals on the indoor unit.
- icomfort system is not able to read the outdoor temperature sensor in the icomfort outdoor unit, check outdoor sensor.
The icomfort does not display an alert code message, but the furnace or unit control displays a diagnostic code.The red Critical Alert icon and homeowner alert button do not display non-critical alerts.Go to the installer program alert button to view all alerts and details about those alerts.
The icomfort thermostat does not dis- play the Model # and or Serial # in- door or outdoor unit.The icomfort control was re- placed with a replacement control before the icomfort system was initially setup or configured.- Replacement icomfort controls do not have the Model # or Serial # loaded in the control.
- The Model # and Serial # cannot be added to the control.
- System will still operate normally.
A non-communicating 2-stage out- door unit was added to the system but the unit only runs in 2nd stage.The “W915 2 Stage Compr” clippable option link on the furnace or air handler control must be cut when used with a non-communicating 2-stage outdoor unit.Cut the “W915 2 Stage Compr” option link on the furnace or air handler control.
Transfer the Model #, Serial # and system settings to a replacement control.The icomfort system is capable of copying settings from the previous configuration to the new compatible device (control) found.Reconfigure the system using the installer program and select the setup button. The system will go through the system discovery process. The thermostat will display missing devices (old control) and found compatible devices (new control). Press the next button to accept the new device and copy the settings. Thermostat will display Settings were copied after successfully copying the information to the new control.
Determine the actual Software version of the thermostat or one of the icomfort unit controls.icomfort software is stored in the control and can be retrieved.From the home screen click the right arrow QD then click service info button; then click the thermostat info button; (display shows model & serial numbers and hardware, software, Wi-Fi revision information).
The icomfort thermostat shows an error code related to the outdoor sensor and or the DAS even after removing these optional accessories.The outdoor sensor and dis- charge sensor are options, how- ever if the system was setup with the sensor in place, the icomfort system will see an open sensor reading if it is disconnected.- Disconnect the outdoor sensor or discharge sensor.
- Using the installer program, reset the system by selecting setup button and follow the screen prompts as the thermostat goes through a new system discovery.
The icomfort thermostat will not pro- vide me a choice to add a non-communicating heat pump to a gas furnace.The icomfort system does not have the ability to control a noncommunicating heat pump on a dual fuel system.Replace the icomfort thermostat with a conventional thermostat that has a dual fuel control mode (e.g. Lennox ComfortSense™ 7000).
During system discovery, the thermostat displays a message Thermo- stat is unable to communicate to system components.The thermostat was not success- ful in communicating to the indoor unit.- Verify the indoor unit has a icomfort communicating control.
- Check wiring connections at R, i+, i- and C at the indoor unit and thermostats.
- Check R, i+. I-, C wires for open/shorts.
Temperature or humidity calibration does not respond to calibration changes.Temperature/Humidity calibration changes will change display 1°F or 1 % RH every 3 minutes.Allow the system to stabilize and complete the calibration mode due to the time delay. A 5°F calibration change will take 15 minutes to calibrate the display.
The installer adjustable settings used to configure the system are not listed in the equipment button under the Thermostat 49W95 (only Temp Reading Calibration and Humidity Reading Calibration are listed as menu items).The adjustable system configuration settings are listed in the equipment button under Sys- tem.- In the installer program select the equipment button and choose System from system device and press edit.
- Over 25 installer adjustable settings are provided including balance point, humidification control, dehumidification modes, stage differentials and delays.

Lennox Ellite Series Thermostats Troubleshooting

If...Then . . .
Key to the right of the screen key is blank.MORE key remains blank unless the Furnace Filter Change Reminder has been turned on.
Display is blank.Check that fresh AAA alkaline batteries are installed as marked on the thermostat.
Temperature settings do not change.Check that temperature settings are:
• Heating 40°F to 90°F (4.5°C to 32°C).
• Cooling 50°F to 99°F (10°C to 37°C).
Heating system does not turn on.• Set the system to heat by pressing the SYSTEM key.
• Check the heat temperature setting to be sure it is set above the room temperature and “Heat On” is displayed solidly on the screen.
• Check the circuit breaker to make sure it is not tripped.
• Check the power switch at the heating and/or cooling system to make sure it is on.
• Check the furnace door to make sure it is closed securely.
• Wait five minutes for the heating system to respond.
• If the problem has not been identified and corrected, contact a qualified service technician.
Cooling system does not turn on.• Set the system to Cool by pressing the SYSTEM key.
• Check the cool temperature setting to be sure it is set below the room temperature and “Cool On” is displayed solidly on the screen.
• Check the circuit breaker to make sure it is not tripped.
• Check the power switch at the heating and/or cooling system to make sure it is on.
• Check the furnace door to make sure it is closed securely.
• Wait five minutes for the cooling system to respond.
• If the problem has not been identified and corrected, contact a qualified service technician.
Cannot set System setting to Cool.Check Installer Set-Up Number 170: Heating and/or Cooling Type. Make sure the setting matches the installed heating and/or cooling system.
’’Heat On” is not displayed on the screen.Set the System setting to Heat and set the temperature setting above the room temperature. If “Heat On” is shown solidly in the display, but the heating system does not turn on
’’Cool On” is not displayed on the screen.Set the System setting to Cool and set the temperature setting below the room temperature. If “Cool On” is shown solidly in the display, but the cooling system does not turn on,
“Wait” is displayed on the screen.Compressor minimum-off timer is activated. Wait up to five minutes for the compressor to turn on.
Fan does not turn on in a call for heat (electric furnaces only)Check Installer Set-Up 0180: Fan Control in Heating. Make sure Electric Heat option is selected.
Both heating and cooling systems are operating at the same time.Check Installer Set-Up Number 170: Heating and/or Cooling Type. Make sure the setting matches the installed heating and/or cooling system.
Check to ensure that bare portions of wires are not touching.
Heating is running in Cool mode.Check Installer Set-Up Number 170: Heating and/or Cooling Type. Make sure the setting matches the installed heating and/or cooling system.
Heating system does not turn off and the heat temperature setting is set below the room temperature ("Heat On” is not shown in display.)Check Installer Set-Up Number 170: Heating and/or Cooling Type. Make sure the setting matches the installed heating and/or cooling system.
Red LED is lit in the upper right corner of the thermostat when the system monitor detects a possible problem.A system monitor is wired to the thermostat L terminal.