Trane Thermostat Troubleshooting (Error Codes, Problem and How to fix it)

Here is a list of some of the most commonly encountered difficulties by Trane thermostat users, along with detailed Trane thermostat troubleshooting for specific issues.

List of Trane Thermostat Troubleshooting

Trane thermostat error codes


Trane Error code 26

Meaning: It’s possible that the unit is hot (the furnace has exceeded the set temperature limit).

Proposed fixes: Because this error occurs due to issues such as a clogged filter, blocked fan, blocked air duct, and dirty air conditioner coil, check these components and clean/clear obstacles as necessary.

Error Code 79

Meaning: Hard lockout (low pressure switch is open).

Suggested repair: In most situations, resetting the unit is the only way to fix the problem, therefore turn off the power to both the inside and outside units to reset the system. If the problem remains, look for a defective low-pressure switch, which is the source of the majority of the 79 error codes.

Error code 89

Meaning: the stats can’t “find” the cooling/heating equipment.

Action: Check for a tripped breaker/blown fuse (to your outdoor unit)- these two are common culprits for error 89. But it can be a wiring problem somewhere in the system so check the wiring too.

Error code 91

Meaning: This fault code may be pointing to an issue of power- a low voltage line (from the furnace) may be lacking power.

What to do: The only option is to check the complete furnace to determine what is causing the problem (Call a Pro if this is beyond you).

Trane error code 126

Meaning: Trane error code 126 typically indicates a communication issue between the HVAC unit and thermostat, often caused by extremely low outdoor temperatures. Here are some key points about resolving this error based on the search results:

Proposed fixes:

  • Cycling the power to the HVAC unit and thermostat can help reset the error code (source).
  • The error can signify a broken electrical circuit or low temperature lockout that prevents operation (source).
  • Checking refrigerant levels and having an HVAC technician top it off if low can address the underlying issue.
  • The thermostat summary table may show the zone expander is offline while other components are online, indicating a communication failure (source).
  • Resetting the thermostat connection and checking wiring between the thermostat and HVAC unit may resolve connectivity issues.

Trane 950 Thermostat error codes

Error code 126

Meaning: There might be a low-temperature lockout (the thermostat may have broken the electrical circuit due to the ambient outdoor temperature dropping too low).

Suggested fix: Try to reset the system. Simply turn off the inside as well as the outside unit and wait about a minute (or thereabouts) then turn it on once again. 

Trane Thermostat error 177.04 

Meaning: The error code 177.04 on a Trane system typically indicates a “Drive Overcurrent” fault. This error suggests that there has been an overcurrent condition detected in the drive hardware of the system. Causes for this error can include:


  • Excessive load: The motor may be working harder than normal due to an obstruction or mechanical binding in the system.
  • Electrical issues: There could be problems with the power supply, such as voltage imbalances or loose connections.
  • Faulty motor or drive: The motor itself or the drive that controls it may be damaged or malfunctioning.
  • Control board problems: The control board can sometimes cause this fault if there are issues with its operation or programming.

When you encounter this error, it’s important to address it promptly, as overcurrent conditions can potentially damage the system. Depending on the cause, the fix may involve clearing obstructions, repairing electrical connections, replacing damaged components, or resetting the system (Fixya). If you’re not experienced with HVAC systems, it’s advisable to contact a professional technician to diagnose and resolve the issue safely and effectively.

Trane 1050 Thermostat error codes

Error code 67.06

Meaning: 67.06 may indicate the suction temperature sensor is experiencing problems in cooling mode- it might have shorted/out of range/circuit is open.


To address the error code CL2.067.06 on a Trane system, which indicates a problem with the suction temperature sensor, follow these steps:

  1. Turn off the power: Before doing any work on the HVAC system, ensure that the power is turned off to prevent any electrical hazards.
  2. Locate the suction temperature sensor: Refer to the Trane system’s manual to find the exact location of the suction temperature sensor.
  3. Inspect the sensor: Check the sensor for any visible signs of damage or loose connections.
  4. Check the wiring: Inspect the wiring leading to the sensor for any signs of damage, corrosion, or loose connections that could be causing the fault.
  5. Test the sensor: Use a multimeter to test the resistance of the sensor. Compare the readings to the manufacturer’s specifications. If the sensor does not fall within the specified range, it may be faulty.
  6. Replace the sensor if necessary: If the sensor is found to be defective, it should be replaced with a new one that matches the specifications for your Trane system.
  7. Clear the error code: After the sensor has been replaced or the issue has been resolved, clear the error code according to the instructions in the system’s manual. This may involve resetting the system or using specific controls on the thermostat or system interface.
  8. Turn the power back on: Once the repair or replacement is complete and the error code is cleared, turn the power back on to the system.
  9. Monitor the system: After the system is back in operation, monitor it to ensure that the error code does not reappear and that the system is functioning properly.

If you’re not comfortable performing these steps or if the problem persists after attempting these solutions, it’s important to contact a professional HVAC technician to diagnose and fix the issue. Handling HVAC components can be complex and sometimes dangerous if not done correctly, so professional assistance is often recommended.

Trane Thermostat Troubleshooting

Trane comfortlink ii Thermostat error codes

Error code 79

Meaning: As mentioned earlier, Error Code 79 simply says “low-pressure switch open”. Causes can be an iced evaporator coil, clogged air filter, low refrigerant, or a defective low-pressure switch.

Potential workaround: Reset the system and check if the error clears. If not, check the above-mentioned parts (evaporator coil, air filter, low-pressure switch). And oh, check the refrigerant.

Trane Touch-screen Thermostat Error Codes

Error code E0

Meaning: Thermistor error.

Action: Check sensor terminals S1 & S2 for tight connection. If wires are properly connected, consider replacing the sensor. Otherwise, the thermostat should be serviced or replaced.

Error code E1 /or “–” flashes in the humidity display

Meaning: Humidity reading outside of measurable range. It can also indicate a fault with the humidity sensor.

Action: Try to power cycle- the internal humidity sensor may recover. And if you suspect that the issue could be caused by an external humidity sensor problem, check the Hs & Hp terminals (Don’t forget to check your remote humidity sensor for damage/malfunction). Replace if necessary.

Error code E4

Meaning: Input voltage is out of range. Range must be between 18 Vac – 32 Vac RMS.

Action: Check the thermostat’s input voltage.

Trane 7CONT624AS42DA Thermostat Troubleshooting

Problem-2 Display will not come on

Possible Reason      

  • Loss of 24VAC between R & C at the Control          


  • Check wiring between R & C
  • Check transformer for 24VAC output
  • Check for broken or shorted thermostat wire

List of Products with Price:

Problem -3 Indoor Temperature display is incorrect    

Possible Reason      

  • The indoor temperature display needs calibrating (always allow 1 hour before calibrating after any power cycle)
  • Heat from the touchscreen is being trapped within the body of the control


  • Calibrate indoor temperature sensor
  • Heat from the touchscreen is being trapped within the body of the control   2) Relocate the control away from any competing air sources or redirect the air sources away from the control

Problem -4 Room temperature overshoots the desired setpoint in cooling mode       

Possible Reason

  • The delta ‘Off in cooling mode is set to a negative number
  • Cooling overshoot is enabled and the indoor RH is higher than the target cooling RH
  • The minimum compressor on time has not been met      


  • Intended operation; if objectionable, change the delta “Off” to 0 degrees
  • Intended operation: if objectionable, disable cooling over- shoot or raise cooling target RH
  • Intended operation; if objectionable, lower minimum on time (lowest setting available is 3 minutes)

Problem -5 Heating or Cooling is being displayed, but no air coming from registers/ vents

Possible Reason      

  • Fan delay time has not expired


  • Wait one minute for blower delay to end, then recheck register/grills

Trane Taystat-370 Thermostat Troubleshooting

Problem -6 Heating or Cooling will not come on.           


  • Check that the SYSTEM switch on the thermostat is set to Heat or Cool.
  • Check if the circuit breaker is tripped—reset the circuit breaker.
  • Check if the fuse is blown— replace the fuse.
  • Check for air movement at the register.
  • Check power to the heating or cooling equipment.

Trane Z Wave TZEMT400AB32MAA Thermostat Troubleshooting

Problem -7

Error code 

  1. LED 1 Green: System Operation display: Sys Off displayed           


  • HVAC system is OFF
  • LED 1 Green: System Operation display: WAIT displayed  


  • Minimum Off Time (MOT)delay is active; LED Off
  • LED 1 Green: System Operation display: Cool On displayed          


  • Cooling system is running; LED On
  • Cooling Min Run Time (MRT); LED On
  • LED 1 Green: System Operation display: Heat On displayed          


  • Heating system is running; LED On
  • Heating Minimum Run Time (MRT); LED On
  • LED 2 Green: System Stage display: No display     


  • 1st stage heating or cooling. LED Off
  • LED 3 Green: Run/Hold/ESM display. Shows state of Schedule Run/Hold Mode: Hold displayed


  • The temperature hold is active. LED On
  • LED 3 Green: Run/Hold/ESM display. Shows state of Schedule Run/Hold Mode: ESM displayed


  • (Energy Savings Mode) The temperature preset is active. LED On
  • LED 4 RED: Alert LED. Used for other system alerts: No display   


  • No alerts or messages. LED Off
  • LED 4 RED: Alert LED. Used for other system alerts: Filter displayed        


  • Filter run timer reached. LED On

Note: Most trane error codes can be fixed by resetting it only, therefore how to reset Trane to fix the error code would be your first choice, for general reset and and for each model reset are in detail down below.

How to Reset Trane Error Codes?

To reset Trane error codes, you can generally follow these steps:

  1. Power Cycle: Turn off the HVAC system at the thermostat by setting it to ‘off‘ mode. Then, go to the circuit breaker box and switch off the breaker that controls your HVAC system. Wait for about 30 seconds to a minute before turning the breaker back on. This can reset the system and clear the error code.
  2. Thermostat Reset: Some Trane thermostats may have a reset button or a specific procedure to reset the system. Refer to the user manual for your specific model for instructions on how to reset your thermostat.
  3. Clearing Specific Error Codes: Some error codes may require specific steps to clear. For example, if the error code pertains to a sensor or other component, you may need to address the underlying issue before the code will clear.
  4. Contacting a Professional: If the error code persists after attempting a reset, or if you’re unsure how to proceed, it’s recommended to contact a professional HVAC technician. They can diagnose the problem and reset the error codes using specific equipment or by resolving the issue causing the error.

Remember, safety should be your primary concern. Always ensure the power is off before attempting to service your HVAC system, and if you’re not comfortable with these steps, seek professional help.

How To Reset A Trane Thermostat

For most units, the most effective method for most units is to switch off the entire system and wait approximately a minute (or thereabouts). After that, you switch it back on.

Here now is how to specifically reset several Trane thermostat models:

How To Reset Your Trane 624 Thermostat For A Heat Pump System

  • Step One: Go To ‘Installer Setting‘ Starting from the main screen of the thermostat, press the ‘Menu’ button.
  • Step Two: Set The Outdoor Unit Type.
  • Step Three: Set The Outdoor Unit Stages.
  • Step Four: Set the Indoor Unit Type.
  • Step Five: Check That The Other Settings Are Correct.
  • Step Six: Return To The Main Screen.

Aside from the methods listed above, how do you delete the schedule from a Trane thermostat? To clear all schedules in the thermostat, press HOLD next to the directional buttons.

The temperature will remain at the desired temperature you set. You can go back to schedule mode by pressing the button under the RUN SCHEDULE display.

How to reset a Nexia Trane thermostat?

Follow these steps To Reset a Nexia Trane thermostat:

  • Check that your system is idle.
  • Next, on your thermostat, press Menu.
  • Tap on Settings.
  • Select Reboot and let the thermostat shut down and then restart.

How to reset trane thermostat after power outage

  • Turn the thermostat to the “Off” position. Wait a few minutes, then turn the thermostat either to “Heat” or “Cool.”
  • Set the thermostat to the desired temperature. Wait a few minutes to listen for the sound of the system turning on.
  • Go to the circuit breaker box if you do not feel or hear airflow. Locate the circuit for the HVAC system. If it is tripped, move it back to the “On” position. If it is already in the “On” position, flip it to the “Off” position and then back to the “On” position.
  • Turn the thermostat off and then on again. Set the temperature to complete the reset process.

How to Reboot Your Trane Wireless Thermostat

XL824/850/1050 Wireless Smart Thermostats Only

  2. On the thermostat screen, press Menu.
  3. Select Settings.
  4. Tap Reboot.
  5. Press Yes to confirm and allow the thermostat to reboot.  The reboot process will take several minutes to complete. (Source: Tranehome)

All other Trane Thermostat  Reboot other than those listed above:

  2. Locate the switch for your thermostat in the breaker box.
  3. Flip the switch to the OFF position for 20-30 seconds.
  4. Return the switch to the ON position.
  5. The reboot process will take several minutes to complete. (Source: Tranehome)

Getting into Trane thermostat manual pdf: Click here

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