Trane Thermostat Troubleshooting

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


Error code 26

Meaning: It’s possible that the unit is hot (the furnace has exceeded 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 stat 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- 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).

Error code 126

Meaning: Trane thermostat error code 126 typically signals communication malfunction between the t-stat and your furnace/AC unit

What to do: We recommend that you turn off both your heater and your air conditioner (and wait a couple of minutes). The devices are then turned back on to see if the fault has gone away.

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 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 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.

Action: Check if the sensor is damaged and replace.

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 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 humidity display

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

  • 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
  • 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


  • 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) 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

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.

Getting in to Trane thermostat manual pdf: Click here

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