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ErrBase

Trane Furnace Reset: How to Clear Lockouts

Quick Answer

To reset your Trane furnace, flip the dedicated power switch on the side of the unit to the off position for 60 seconds. If there is no switch, toggle the furnace breaker in your main electrical panel. This power cycle clears soft lockouts and allows the control board to restart its ignition sequence.

Honestly, nine times out of ten when I get a call about a Trane that won't turn on, it's just stuck in lockout. The board shuts everything down to protect itself. Ignore it long enough in January and you're looking at frozen pipes. A power cycle fixes most of these in under five minutes. But if it keeps locking out after you reset it, the board's telling you something's actually broken.

TraneFurnace

How to Reset Your Trane Furnace

Here's the thing about Trane furnaces: they don't have that little red reset button you see on old oil burners or some Bryant units. The whole reset lives on the control board, so you've got to kill power completely to clear it. I did three of these last week during the cold snap. Usually takes less time than it takes to find the breaker. Most resets run you zero dollars if the underlying cause is just a dirty filter or a power hiccup.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Dirty Air Filter45%
Flame Sensor Soot30%
Thermostat Communication Error15%
Power Surge or Brownout10%

Symptoms You May Notice

  • The blower fan is running and you feel air coming from the vents, but it's room temperature air, no heat whatsoever.
  • Thermostat shows it's calling for heat but the furnace is completely silent. No click, no rumble, no inducer spinning up. Just nothing.
  • Red LED on the control board is blinking in a repeating pattern, like three flashes then a pause then three more, over and over.
  • You hear the inducer motor spin up, then a couple of rapid clicks from the igniter, then the whole thing shuts off about 5-8 seconds later before it ever really got going.
  • It tries to start on its own every 5-10 minutes, clicks a few times, can't catch, and goes quiet again.

Tools Required for Diagnosis

Phillips #2 screwdriverFlat-head screwdriverDigital multimeter (Fluke 117 or similar)Replacement furnace filter (check size printed on your current filter frame)Flashlight or headlampPhone or camera to photograph LED flash code patternFine steel wool or dollar bill (for cleaning flame sensor)

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Frequently Asked Questions

Where is the reset button on a Trane furnace?
Most modern Trane gas furnaces don't have a reset button on the outside. The reset is just the power switch or the circuit breaker. That said, if you open the cabinet on some older models, you might find a small manual reset button on the high limit switch or the flame rollout switch. Those are safety devices, they're not meant for routine resets. If you're pushing one of those buttons more than once, something is wrong and it keeps tripping for a reason. Find out why before you push it again.
How many times can I reset my furnace before calling a pro?
Two strikes and you're done. Reset it once, let it run a full heat cycle, see if it holds. If it locks out again within 24 hours, stop resetting it. Repeatedly cycling a furnace that has a real fault can crack the heat exchanger from thermal stress, and that's a $1,500 repair minimum on a Trane. Or worse, it means unburned gas is accumulating somewhere. A service call is $80-150. A cracked heat exchanger or a carbon monoxide situation is way more expensive in every possible way.
Why does my Trane furnace keep going into lockout?
The three most common reasons I see on Trane units are a dirty flame sensor, a clogged filter tripping the high limit, or a backed-up condensate drain on high-efficiency models. The flame sensor is actually a pretty easy fix if you're comfortable opening the cabinet. It's a small rod with a wire on it, and you can clean the oxidation off with light steel wool or a dollar bill. Takes 10 minutes. If it's not one of those three, pull the flash code off the LED and look up what it means for your specific model.
Will a reset fix a blinking red light on my Trane?
Maybe. A reset might clear the light, but the blinking pattern is actually a diagnostic code the board is broadcasting. Count the flashes before you reset anything. Write it down. That code tells you exactly what part is failing, which saves you from buying the wrong thing or having a tech spend 45 minutes diagnosing what the board already told you for free. After you note the code, then do the reset. If the same code comes back, you've got a real component problem, not a fluke.
Does unplugging the furnace reset it?
Yes. If your furnace plugs into a standard 120V outlet, pulling the plug for 60 seconds does the exact same thing as flipping the breaker. The board loses power, capacitors drain, fault memory clears, clean reboot. Most Trane gas furnaces run on 120V for the controls even though they're usually hardwired. If yours has a plug, use it. Just make sure you wait the full minute.
My Trane furnace resets fine but goes out again overnight. What's going on?
That's a pattern I see a lot in late fall. What's usually happening is the flame sensor is dirty enough that it works when the furnace is warm but fails on a cold start. So it runs fine for the first cycle, sensor warms up, works. Overnight the furnace cools down completely, it tries to start cold, can't prove flame, lockout. Pull that flame sensor and clean it with steel wool. Part number depends on your model but they're usually under $20 if you end up needing a replacement. If cleaning doesn't fix it, the sensor's done.

Models Known to Experience RESET-PROCEDURE Errors

This repair applies to most Trane furnaces with this error code. Common model numbers include:

TUX1B080A9421A, TUD2B060A9V3VA, S9X2B060U3PSA, TDD1B080A9361A, TUE2B100A9421A, S8X1B080M4PSAA, TUX2B040A9241A

RP

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 17, 2026