Trane Furnace Red Light Flashing 3 Times [Solved]

Trane Furnace’s red light flashing 3 times tells you either there is an issue with your furnace pressure switch or a fault with the ventilation. Plus, clogged inducer fans, blocked condensate drain and pumping lines are also responsible for the red light blinking 3 times.

trane furnace red light flashing 3 times

To fix your furnace’s 3 blinking instantly, check and validate that all the connections to the pressure switch are okay. But, with a faulty pressure switch, simply replace it.

 Besides, make sure there is enough airflow through the vent system and clean the blockage between the condensate drain and pumping lines.

Yet, if you find the red light flashing 3 times is still, then go on reading our comprehensive guide to learn in detail. You will definitely get the solution.

Trane Furnace Red Light Flashing 3 Times [Solved]

In this article, you will find out the common causes and ultimate solution to the Trane Furnace Red Light Flashing 3 Times. So let’s get started.

Note: You can also read how to fix all read light blinking with Trane Furnace.

1. Malfunctioning Of The Pressure Sensor Switch

The pressure switch is an essential element of any furnace which senses pressure within the flue system. It is mainly a safety sensor that prevents the system from overheating. It functions by building up a connection to pass power through it. 

malfunctioning of the pressure sensor switch

But when your Trane furnace’s manual shows three (3) times red light flashing, then it means there is an issue with the pressure sensor switch or faulty pressure switch.

The sensor switch gets faults due to a clogged port on the collection chamber by calcium deposits, dirt, or other debris. Also, for obstruction in the flue or for faulty connection with the flue system, the furnace pressure switch fails to continue its operation. As a result, the switch can’t allow power to ignite the light.

Now, let’s explain how to fix it.


  • First, remove the front access panel of your furnace.
  • Now, locate the pressure sensor switch and inspect all the switch connections. Ensure that they are in the right position.
  • After that, check if they have too much moisture on them. If it happens, remove the debris as soon as possible.
  • Then, disconnect the 24-volt wires from the switch. This time, you have to measure the voltage of the sensor.
  • Take an ohm meter and connect it to the switch. The reading should be at 0 as the switch has closed. But when it is opened, your meter will read 24 volts.
  • Anyway, if the reading is not at zero, be sure it is defective. You need to replace it ASAP.
  • But in the case of correct reading, then relax. It is simply a sensor problem, and you can definitely fix it. 
  • Do a power cycle on the furnace unit. For this, flip the breaker connected to your furnace. 
  • Now, just wait for about 30 minutes and invert the flip again. 
  • Finally, your furnace will be right shortly. If not, check the below section. 

2. Blocked Furnace Hose

After replacing the pressure sensor and still, you are getting the same flashes, be sure the blocked hose of the sensor is the second culprit. At the bottom of the sensor, there has a small white flexible hose attached to it. 

It runs down into the air intake area. Also, on the exhaust side, the sensor splits into two hoses. One is attached to the gas valve, and another one is connected to the burner.

 Anyway, if the hoses are get obstructed by debris, it affects the sensor function. After long wear and tear, there may create cracks and holes in the hoses. However, this time, we will concentrate on the hoses and will fix all the problems:


  • First, inspect the hoses. Check if the hoses are blocked by debris.
  • Clean out the hoses and make them unclogged completely.
  • Also, there should not be any rips and tears on the hoses.
  • Apart from all the above, you will see small nipples where the hoses are attached. There may have been crud, and make it blocked. Clean it out as well. You can use an opened paper clip or a small stiff wire and put it through the fitting. It will easily clean the fittings all the way through.
  • Make sure the hose from the pressure switch is connected end to end.
  • Don’t miss the barb coming from the burner box by sticking a paper clip in and out a few times.
  • Finally, replace the extremely defective hoses or tubes. If it seems hard to you, take help from professionals.

3. Plugged Up Condensate Drain

Among all responsive factors for causing such errors, plugged-up drainage is one of the most common reasons.

All condensate drains of the furnace go into a trap. This trap is quite mandatory for a high-efficiency furnace system. But the one and only downside of the drainage is a blockage inside. 

condensate drain sloped towards

The drainage may be stuck by debris and specks of dirt. It falls a great effect on the furnace system.

Proper maintenance is quite needed for this drainage system to prevent the furnace from overheating. Sometimes, improper setting of the venting system creates malfunctions. 

Follow the below instructions to ensure proper drainage of the system:


  • First of all, look through that each condensate-producing component is sloped towards the drain.  
  • Check out the exhaust vent. You have to ensure that the venting has slopped down towards the furnace at least 1/4” solps per foot of length. Also, there should not be any sags between the pipe hangers.
  • Then verify that fluent water flow through the trap from all its ports. 
  • Clean the trap and make it dirt free. You can use hot water to stubborn blockages easily. 
  • Now, check if the red light flashing issue has been resolved or not. 

4. Clogged Furnace Ventilations

Proper ventilation of the furnace is quite needed for continuing the normal process of the system. But, the ventilation system will raise an issue when the vents are blocked by debris and create restrictions in airflow.

clogged venting pipes

You may find the blockage in the chimney, motor, air filters, or combustion air vent. Due to all these, the combustion air pressure system cannot provide enough airflow through the vent system.

Our experience says that it may happen if there is a clog of dust, leaves, or bird’s nest in the venting pipelines. 


  • First, turn off your furnace.
  • Unscrew the furnace vents to get access to them.
  • Examine each of the venting pipes. Make sure they are free of debris.
  • Use a vacuum cleaner to suck up all the debris from the vents preciously. 
  • Clean the stuck specks of dirt using a brush.
  • Double-inspect the induced fan. Ensure the motor is running well as usual.
  • If there is not enough air coming out, call an expert to repair it. Finally, it is wise to change your motor or air filter entirely.

5. Inducer Fan Problems

In the furnace system, a draft inducer is an essential element located inside of the exhaust flue that is at the far end of a furnace’s heat exchanger.

 inducer fan problems

The chimney has a close connection to the inducer housing. This area is related to the pressure switch. 

There are several reasons behind the failure of the inducer fan peaceful movement like damaged wiring, broken motor, and wearing out of the internal bearings.  

Mainly, the inducer motor or fan helps to vent unexpected gas out of the chimney and the flue. So, when the fan doesn’t work well, you will get a code that is related to inducer issues.


Though most of the problems here require calling an expert, you can simply try the tips to fix the issue.

  • Turn off your furnace first.
  • Inspect if the inducer fan is running smoothly.
  • First, try to spin the fans manually. If it is not spinning freely, be sure the fans have a blockage. 
  • Clean out the debris from the chimney and fans.
  • Make sure there is not any ice blocking.
  • If needed, replace the defective fan motor
  • Hopefully, your furnace is now free from any type of error code. 

More Effective Ways To Fix Your Trane Furnace Blinking Red-light Issue

If the above tricks fail to solve the blinking red-light issue, you can fix the igniting issue instantly. Simply, by restarting your furnace, you can get your expected solution. Let’s go to the effective steps below…

  • Go to your diagnosis process.
  • Locate the reset button and reset the switch.
  • Unplug your furnace and wait for 5 minutes.
  • Next, turn it on again and hope it will solve your flashing problems.

Examine The Furnace:

After following the tips, your furnace reset has become brand new. Now, we strongly believe that your furnace will work as usual. Take care of your furnace in order to keep it fit season after season. If you cannot get the expected results, consult with an HVAC technician for the next action.


What is the red light on the Trane furnace?

The red light indicates certain problems with various codes. The flashing times primarily show what problems are detected with your furnace. Like all other manufacturers, the Trane furnace manual chart indicates that there are some common issues with your furnace.

Why is my Trane furnace’s red light remaining off?

It is normal for your heater to have a red light. But if it remains completely off, your furnace’s ignition system has lost power. So, it can not operate its blinking activities. 

How can I detect 2 & 4-time error flashing codes?

There are simple ways to detect flashing error codes in your furnace. Two flashing lights indicate that there has been a lockout. It hinders catching a flame. And, 4 flashes show open over-temperature limit circuit problems.

Why is a pressure switch important?

A pressure switch acts as a bridge to pass power through the connections. To light up, it is activated by the air pressure by the inducer and draft inducer. The switch has a close connection to the igniters.

How can I avoid ignition issues?

It is important to know the ignition issue to prevent a major downfall. All the problems that arise are because of a lack of maintenance and service. Sometimes, you can’t solve certain problems alone. It is wise to consult with professionals to repair timely your flashing issues. So, take care of your furnace to avoid difficulties.


The main purpose of this article is to find out the flashing problems with your Trane Furnace. And, we have explained clearly why the Trane Furnace Red Light is flashing 3 times and given their simple solutions.

Hopefully, in the meantime, you have figured out the causes and learned how to solve the frequently flashing issues. Therefore, follow the tips to fix it as mentioned throughout our guidelines.

Then, if you encounter any issues, don’t hesitate to consult with an expert to repair your furnace’s blinking issues. Thanks for staying tuned to us. 

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.

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