Trane Furnace Red Light Flashing [All Blinks Solved]

Most often, Trane furnace owners experience flashing red light issues on their furnaces. The Trane furnace red light flashing basically corresponds to the specific error codes in the furnace unit. 

trane furnace red light flashing

While operating, the red light may start flashing 1, 2, 3, 4, 5, 6, 7, 9, or constantly. These types of errors primarily indicate that the system has been locked out from its normal operation currently. 

But each error code means different things depending on the number and speed of the light blinking. Today, we are going to explore each of the errors with detailed information regarding the reasons and simple solutions. So, let’s get started…

Go through our comprehensive guide to find the corrective approaches to fix any error codes on the Trane furnace.

1. Red Light Flashing 1 Time [No Call For Heat]

The trane furnace’s red light flashing 1 time means that the system is not getting any calls for heat. So, it means that the unit is waiting for the signal from the thermostat.

set the correct time and date on the thermostat

Sometimes, the light will still flash even setting the temperature. Anyway, note down the possible reasons why the furnace is not responding to the thermostat:

  • Clogged air filter
  • Wrong installment for the thermostat
  • Loose and damaged wiring
  • Defective circuit breaker
  • Blown fuses

Here are the needed solutions steps that you should follow to fix the issue:


  • First of all, check the circuit breaker and the surrounding wirings.
  • Tighten the loose wire and replace the defective ones.
  • Replace the blown fuse as well.
  • Now, inspect the thermostat. Set the mode to ‘heat.’ Replace the damaged batteries and loose wires from the device.
  • Also, make sure the correct time and date are on the thermostat. Verify a proper installment of the device on the wall.
  • Then, locate the air filter. Clean the clogged debris from the filter to prevent airflow restrictions.
  • The red light flashing issue should be resolved.

2. Red Light Flashing 2 Times [External lockout]

Trane Furnace’s red light blinking 2 times tells you there is an external lockout on the furnace.

This is one of the most common error codes that Trane furnace users face. When there have glitches in the power supply, the furnace catches this error. 


  • First, turn off your furnace, And turn off the pilot light as well.
  • Now locate the reset button of the furnace. Basically, you will find the reset button inside the blower housing. After accessing the reset button, press it.
  • Keep holding the button for about 30 seconds. Make sure you are not pressing the button so hard.
  • You will hear a beep sound from the unit. If yes, release the button and wait until the noise has gone out. It will do a hard reset on the furnace.
  • If your furnace has not a reset button, just leave the furnace unplugged for some time. Don’t forget to turn off the furnace breaker.
  • Then, turn on the furnace. 

For your better understanding, you can read our comprehensive guide on how to fix Trane Furnace blinking 2 times.

3. Red Light Flashing 3 Times [Pressure Switch Error]

Trane Furnace’s red light blinking 3 times indicates the draft pressure error. A pressure switch is an essential piece of equipment for the furnace which works through a safety mechanism to protect the system from overheating. 

Basically, it senses pressure within the flue system. Malfunctioning from this switch leads to the 3 times errors on the red light.

Here we have explored the step-by-step solutions to check out the faulty pressure and the tips to resolve the issue. 


  • First, remove the front access panel. Now locate the pressure switch. You will find 24-volt wires connected to the switch. Disconnect the wires very carefully.
  • This time, measure the voltage of the switch using an ohm meter. Measure the voltage as soon as the fan begins to run. It should be zero.
  • If not, be sure the pressure switch is defective. Replace it. Also, if you get a zero reading, do a power cycle on your furnace by unplugging it for about 30 minutes.
  • Meanwhile, check out the inducer fan. Spin it manually. Remove the obstruction from the fans. Then, inspect the venting pipes. Make sure the pipes are completely unclogged.
  • Now, check if the flashing has gone away. 

4. Red Light Flashing 4 Times [Tripped High-Limit Switch]

It is a common scenario of the Trane furnace that the red light blinks four times and blows cold air only. Flashing 4 times on the red light mainly notifies that the high limit switch has been tripped. 

clogged air filter

One of the leading causes of tripping a high-limit switch is a clogged air filter. If the air filter is blocked by debris, the flame sensor fails to detect temperature accurately, and the furnace gets overheated. 

Blockage in the air filter creates obstruction in airflow, and the furnace stops blowing hot air as a safety mechanism.

Faulty wiring or installation and dirty flame sensor rod are other possible reasons for this.  Whatever the reason is, follow our below instructions to fix the Trane furnace 4 times blinking issue.


  • First, you have to reset the heater by unplugging it for some time. 
  • Then, concentrate on the air filter. Clean out the debris from the filter and around the system.
  • Unblock the flame sensor rod and furnace blowers to prevent overheating issues from the unit.
  • Take a look at the pilot light. Replace the defective pilot light.
  • Ensure a stable installation of the furnace.
  • If all the above steps fail to resolve the issue, be sure the high-limit switch gets defects. Replace your Trane furnace high-limit switch as soon as you can.

5. Red Light Flashing 5 Times [Flame Detect Fault]

Most of the time, the Trane furnace catches the error code of 5. When the red light starts blinking five times, it tells that the unit sensed a flame in such a period when no flame should be present. 

So, the problem is related to the flame sensor. A faulty flame sensor never detects the heat that has been turned on. Either the sensor is cracked, broken, or cracked. 

This may happen after long wear and tear. Also, the problem may start from a gas valve that has closed slowly or the burner flame lingering. It may be stuck by debris or leaking gas. 


  • Turn off the furnace first.
  • Then turn off the gas valves. 
  • Now, unscrew the mounting screw. 
  • Clean the valves properly and ensure they are completely blockage free.
  • Repair for leaking gas on the unit. 
  • Now, remove the flame sensor carefully.
  • Verify if the sensor is dirty or burnt out. Clean it properly.
  • If the sensor is broken or cracked, replace the defective sensor.

6. Red Light Flashing 6 Times [Power Reversed Polarity Or Poor Grounding]

Six times red light blinking on the Trane furnace mainly signals a reversed polarity issue or poor unit grounding. That means the AC power has reversed or the supplied voltage is too low. 

Here the furnace control board is sensing the reversed polarity. In short, the heater is facing a glitch power supply. Also, if the furnace is not installed on stable ground or placement, the unit will catch the same error code. 


  • First of all, check out all the wiring connectors of the furnace. Replace the damaged and cracked wiring.
  • You have to ensure that the black hot wire has about 120 V to ground. Also, the white neutral wire has to be zero volts.
  • The neutral wire should not be connected to the place where the hot wire is connected. It will ensure the correct polarity of the furnace. Now, disconnect the electrical plug from the wall outlet.
  • Leave the furnace unplugged for some time and do a power cycle through the unit. It will assist in eliminating the power glitches like power spike, which is the culprit of giving the code on the board.
  • Finally, you have to ensure the igniter’s proper grounding. It should not be grounded through any cracked place in the ceramic base.
  • Verify the stable installment of the furnace as well. After resolving the igniter and wiring issue and still, you are getting the same code, replace your furnace control board.

7. Red Light Flashing 7 Times [Gas Valve Circuit Error]

If the Trane furnace red light is blinking 7 times error codes, be sure there has a circuit error on the gas valve.

That means either the gas valve is stuck by debris or blocked. Sometimes, leaking gas from the valve leads to the same error code. The other possible reasons are:

  • Faulty hot surface igniter
  • Malfunctioning of the burner system
  • Faulty flame sensor,
  • Defective control board
  • Blown fuses


  • First of all, power off the furnace at the breaker. Check the circuit breaker and the wiring. Replace the blown fuses.
  • To troubleshoot the issue, you have to locate and check out the gas valve. Clean out the valves and make them clogged-free.
  • Now check for gas leaking from the valve. You can use a carbon monoxide detector for this. Also, you may use soapy spray on the fitting to verify the bubbles. Repair the gas leakage. 
  • Replace the defective gas valve if needed. If replacing the valve fails to resolve the issue, there may have a poor signal from the flame sensor. Clean out the flame sensor. 
    • Clean out the complete burner system across from the flame rod. If needed, replace the defective control board.

8. Red Light Flashing 9 Times [Igniter Issue]

The Trane furnace’s red light blinking 9 times specifically determines the igniter issue of the unit. The problem started with the Hot Surface Igniters.

red light flashing 9 times or igniter issue

Also, if the furnace is not receiving power properly or for a lower voltage supply, the red light will flash. 

Improper grounding of the igniter and malfunctioning of the thermostat can cause this as well. However, here is the included solution procedure to fix the issue efficiently:


  • Turn off your furnace before starting.
  • Now check the igniter.
  • Check for any visible damage signs on the igniter. Replace the faulty hot surface igniter.
  • If the igniter replacement can’t solve the issue, ensure that the furnace is receiving power.
  • Inspect all the wiring connections. Replace the damaged ones. 
  • Check out the thermostat as well. Replace the defective thermostat.

You can also watch the tutorial to replace the hot surface igniter.

9. Trane Furnace Red Light Flashing Constantly

If your furnace’s red light is flashing continuously, there is no problem with your unit. All the operation is quite normal, and you needn’t be concerned about continuous flashing.

If the red light blinks in numbers, be sure the furnace has a problem. It indicates that the system is locked out of its normal function.  


How do I reset my Trane code?

To reset the error code from the Trane furnace, you just need to reset the circuit breaker. Just disconnect the furnace from the breaker and leave it unplugged for some time to reset the code. 

Where is the reset button on a Trane xr95 furnace?

All Trane furnaces model has figured a reset button. You will find the red-figured reset button near the burner of the furnace. You can reset the unit by pressing the button.

Where is the pilot light on the Trane furnace?

You can locate the pilot light on the bottom of your furnace. The pilot light is controlled by a control knob.

It’s A Wrap!!

Well!! After reading the complete article, now you have a crystal clear about each of the error codes on the Trane furnace. You can easily troubleshoot the flashes by following the above solution procedures effectively. 

But still, if you have any further queries regarding Trane Furnace’s red light flashing issues or other, don’t be late to ask us through comments. We will reply to you ASAP with possible solutions.

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

4 thoughts on “Trane Furnace Red Light Flashing [All Blinks Solved]”

  1. Just making sure since the red light is blinking constantly with no brakes in between that nothing is wrong and I should not be concerned, right? I appreciate your help.

    • Hi Stephen

      Yes, if your furnace’s red light is flashing continuously, there is no problem with your unit. All the operation is quite normal, and you needn’t be concerned about continuous flashing.

      Wish you all the best!

  2. Hello,

    My Trane XR90 is blinking continuously but the unit will not start. I think it is slow blinking, meaning it is not getting a signal to heat from the thermostat. What should I check? What wires from the thermostat tell the furnace to turn on?

    • Hi Brett

      Generally, a furnace doesn’t respond to the thermostat due to a clogged air filter, the wrong installment for the thermostat, loose and damaged wiring, a defective circuit breaker, or blown fuses.

      Well, to fix the issue, do the followings-

      1. First of all, check the circuit breaker and the surrounding wirings.
      2. Tighten the loose wire and replace the defective ones.
      3. Replace the blown fuse as well.
      4. Now, inspect the thermostat. Set the mode to ‘heat.’ Replace the damaged batteries and loose wires from the device.
      5. Also, make sure the correct time and date are on the thermostat. Verify a proper installment of the device on the wall.
      6. Then, locate the air filter. Clean the clogged debris from the filter to prevent airflow restrictions.

      Hopefully, your problem will be solved.

      Best of luck!


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