Got furnace problems? No worries, even the best of the best furnaces can run into issues. But the good news is, most furnaces have built-in safety features that can send out error codes to help you and your repair pro diagnose the issue.
These codes can vary depending on the brand, but the way they’re read and the problems they indicate are usually pretty similar. Let’s explore some of the most frequent error codes and their meanings.
There are many different furnace brands, each with slightly different error codes. However, the way a code is read and the problems it indicates are usually very similar across brands. So, whether you have a Carrier, Lennox, or any other brand of furnace, you’ll likely be able to understand the error code and take the appropriate action.
By understanding these codes, you’ll be able to work with your repair professional to diagnose and fix the issue as quickly and efficiently as possible. To help you get started, let’s take a look at some of the most common furnace troubleshooting codes and what they mean.
Here is our Guide to Furnace Error Codes:
- Lennox Furnace Codes: Lennox Flashing Light Codes
- Trane Furnace Error Codes: a Fault Codes List
- Goodman Furnace Codes: What Fault Codes Mean
- Amana Furnace Codes – Furnace Problem Troubleshooting
- Ducane Furnace Troubleshooting — What the Error Codes Mean
- Carrier Furnace Codes: Furnace Yellow Light Error Codes
- American Standard Furnace Error Codes
- Bryant Furnace Error Codes
- Rheem Furnace Error Codes
- Ruud Furnace Error Codes
Furnace Light Codes — Reading Your Furnace Error Codes
Want to know how to read your furnace error code? No matter what brand of furnace you have, they all typically use a series of flashing lights to communicate any issues. To decipher the code, just locate the LED light and take note of its flashing pattern – count how many times it’s flashing and at what speed. For the specific meaning of the code, check the installation manual for your furnace.
To make it easier, here are some of the most common error codes that homeowners may encounter.
Lennox Furnace Codes: Lennox Flashing Light Codes
Do you own a Lennox furnace at home? If so, the heating specialists at TEK in Vancouver are knowledgeable with the Lennox brand and are here to assist you. In case your Lennox furnace is malfunctioning, here is some useful information for you.
Blinking Light On A Lennox: Why Is Your Lennox Furnace Light Flashing?
Just like Trane and Amana, Lennox furnaces are equipped with LED lights that indicate any issues. But, Lennox HVAC systems differ in the way they communicate problems. Instead of using only one color, they use both red and green lights to convey error codes. These lights blink in specific patterns to represent specific issues.
If you see both the red and green lights flashing quickly or slowly at the same time, it means that your furnace is functioning properly. However, any other pattern indicates a problem that might require repair.
To understand Lennox error codes, you need to pay attention to both the color of the flashing light and the speed of the blink. Here are some common error code patterns and what they indicate:
1. Lennox Furnace Error Codes:
LENNOX RED LIGHT FLASHING QUICKLY AND GREEN LIGHT FLASHING SLOWLY
Meaning: Reversed polarity
Potential Issue: Electrical wiring issue
LENNOX RED LIGHT FLASHING SLOWLY AND GREEN LIGHT FLASHING QUICKLY
Meaning: Low flame error
Potential Issue: Flame sense rod issue, dirty flame sensor, poor gas pressure, etc.
LENNOX RED LIGHT FLASHING SLOWLY AND GREEN LIGHT SOLID
Meaning: High limit switch open
Potential Issue: Plugged filter, dirty blower wheel, ductwork issue, etc.
LENNOX RED LIGHT OFF AND GREEN LIGHT FLASHING SLOWLY
Meaning: Draft inducer or pressure switch failure
Potential Issue: Blocked inlet or exhaust vent, cracked hose, draft inducer not working, short in power switch, etc.
LENNOX RED LIGHT ON, ON, OFF AND GREEN LIGHT ON, OFF, ON
Meaning: Circuit board failure
Potential Issue: Control panel or wiring issue
LENNOX RED AND GREEN LIGHTS ALTERNATING, FLASHING SLOWLY
Meaning: Flame failure
Potential Issue: Pilot light or ignition sensor issue
LENNOX RED AND GREEN LIGHTS ALTERNATING, FLASHING QUICKLY
Meaning: Issue with voltage
Potential Issue: Improper main ground
Trane Furnace Error Codes: A Fault Codes List
Trane furnaces are a reputable brand, but sometimes problems may arise. To diagnose the issue with your Trane furnace, check out these common error codes indicated by a blinking red light. The meaning of the error code is determined by the blink frequency and pattern.
2. Trane Furnace Error Codes:
TRANE FURNACE CONSTANT SLOW BLINKING
Furnace is functioning normally
TRANE FURNACE CONSTANT FAST BLINKING
Furnace is functioning normally
TRANE FURNACE RED LIGHT CONSTANT ON
Potential Issue: Control panel issue
TRANE FURNACE RED LIGHT CONSTANT OFF
Potential Issue: Power off
TRANE FURNACE 2 BLINKS
Flame failure (retries exceeded)
Potential Issue: Gas supply issue, flame rod not sensing flame, wiring issue, etc.
TRANE FURNACE 3 BLINKS
Pressure switch problem
Potential Issue: Blockage in vent, condensate drain plugged, etc.
TRANE FURNACE 4 BLINKS
Temperature switch problem / Over temperature limit
Potential Issue: Plugged filter, plugged secondary heat exchanger, ductwork issue, etc.
TRANE FURNACE 5 BLINKS
Flame sensed when no flame should be present
Potential Issue: Leaky gas valve, stuck gas valve, defective flame sensor, etc.
TRANE FURNACE 6 BLINKS
115 VAC power reversed polarity, poor grounding
Potential Issue: Issue with line voltage polarity or wiring, etc.
TRANE FURNACE 7 BLINKS
Gas valve circuit error
Potential Issue: Gas valve issue
TRANE FURNACE 8 BLINKS
Low flame sense signal
Potential Issue: Flame sensor malfunction, low gas pressure, etc.
TRANE FURNACE 9 BLINKS
3. Goodman Furnace Codes: What Fault Codes Mean
GOODMAN FURNACE FAULT CODE LIGHT ON
Meaning: No signal from thermostat
Potential Issue: Thermostat not properly connected, issue with thermostat setting
GOODMAN FURNACE FAULT CODE LIGHT OFF
Meaning: Control failure
Potential Issue: No power, issue with connections
GOODMAN FURNACE FAULT CODE 1 FLASH
Meaning: Ignition error (retries exceeded) / Flame failure
Potential Issue: Faulty or dirty flame sensor, faulty igniter, gas supply interruption, etc.
GOODMAN FURNACE FAULT CODE 2 FLASHES
Meaning: Pressure switch error (stuck closed)
Potential Issue: Short in the pressure switch circuit, faulty pressure switch, draft inducer not working, etc.
GOODMAN FURNACE FAULT CODE 3 FLASHES
Meaning: Pressure switch error (stuck open)
Potential Issue: Blockage in pressure switch hose, pressure switch hose improperly connected, loose wiring, induced draft blower operating when it shouldn’t be, etc.
GOODMAN FURNACE FAULT CODE 4 FLASHES
Meaning: Open high limit
Potential Issue: Dirty filters, wiring issue, blockage in flue, etc.
GOODMAN FURNACE FAULT CODE 5 FLASHES
Meaning: Flame sensed with gas valve off (i.e. no call for heat)
Potential Issue: Leaky gas valve, gas valve stuck open, defective flame sensor, etc.
GOODMAN FURNACE FAULT CODE 6 FLASHES
Meaning: Open rollout switch
Potential Issue: Blocked or cracked heat exchanger, blocked vent, low gas pressure, etc.
GOODMAN FURNACE FAULT CODE 7 FLASHES
Meaning: Low flame error
Potential Issue: Low gas pressure, faulty flame sensor, dirty flame sensor, etc.
GOODMAN FURNACE FAULT CODE 8 FLASHES
Meaning: Ignitor error
Potential Issue: Faulty ignitor, ignitor not properly connected, wiring issues, etc.
GOODMAN FURNACE FAULT CODE 9 FLASHES
Meaning: Open pressure switch, induced draft blower on
Potential Issue: Pressure switch hose cracked, blocked or improperly connected, faulty pressure switch, etc.
GOODMAN FURNACE FAULT CODE CONTINUOUS FLASHING
Meaning: Reversed polarity
Potential Issue: Issue with wiring
Amana Furnace Codes – Furnace Problem Troubleshooting
Looking for assistance with your Amana furnace? Check for its fault code. Having the error code ready for your repair specialist will make it easier and faster for them to resolve the issue.
Below are some common Amana furnace fault codes you might encounter.
4. Amana Furnace Error Codes:
AMANA FURNACE CONSTANT RED LIGHT
No signal from thermostat.
Potential issue: No power, issue with connections.
AMANA FURNACE CONSTANT FLASHING
Potential issue: Issue with wiring or line voltage polarity.
AMANA FURNACE 1 FLASH
Flame failure / Lockout due to excessive ignition retries.
Potential issue: Gas supply interruption, flame rod not sensing flame, wiring issue, etc.
AMANA FURNACE 2 FLASHES
Draft inducer not operating or pressure switch failure (closed pressure switch circuit).
Potential issue: Draft inducer not working, short in the pressure switch, blockage in vent, condensate drain plugged, etc.
AMANA FURNACE 3 FLASHES
Open pressure switch.
Potential issue: Pressure switch needs to be replaced, pressure switch hose improperly connected or blocked, loose wiring, etc.
AMANA FURNACE 4 FLASHES
Pressure error / High limit error.
Potential issue: Clogged air filter, drain tubes obstructed by debris or moisture, faulty wiring, etc.
AMANA FURNACE 5 FLASHES
Flame sensed without call for heat.
Potential issue: Valve closing too slowly, etc.
AMANA FURNACE 7 FLASHES
Faulty flame sensor.
Potential issue: Flame sensor dirty or too far from flame, etc.
Ducane Furnace Troubleshooting — What The Error Codes Mean
When encountering problems with your Ducane furnace, be sure to check for the error codes. Ducane furnaces use a combination of red and green flashing LED lights to indicate the problem. If you see a green LED light, it means there is a demand for high heat.
Here are some common Ducane furnace error codes to look out for:
5. Ducane Furnace Error Codes:
DUCANE FURNACE RED LIGHT ON
DUCANE FURNACE RED LIGHT OFF
No power Issue with power source, connections or breaker
DUCANE FURNACE RED LIGHT 1 FLASH
Flame present with gas valve off Dirty flame sensor rod, valve closing too slowly, etc.
DUCANE FURNACE RED LIGHT 2 FLASHES
Pressure switch error (pressure switch closed with inducer off) Issue with pressure switch, draft inducer not operating, debris in line, cracks in tubing, etc.
DUCANE FURNACE RED LIGHT 3 FLASHES
Low fire pressure, rollout or limit switch open
Blocked or cracked heat exchanger, blocked vent, low gas pressure, etc
DUCANE FURNACE RED LIGHT 4 FLASHES
High limit switch open
Clogged filter, dirty blower wheel, etc.
DUCANE FURNACE RED LIGHT 6 FLASHES
Pressure switch cycle lockout
Faulty pressure switch, blocked vents or condensate drain pipe, etc.
DUCANE FURNACE RED LIGHT 7 FLASHES
Lockout due to no ignition
Faulty or dirty flame sensor, faulty igniter, dirty filter, etc.
DUCANE FURNACE RED LIGHT 8 FLASHES
Lockout due to too many flame dropouts
Dirty flame sensor, flame sensor or igniter failure
DUCANE FURNACE RED LIGHT 9 FLASHES
Polarity and phasing error Issue with wiring.
DUCANE FURNACE GREEN LIGHT FLASHING
High heat demand, high pressure switch open
Dirty filter, dirty blower wheel, etc.
6. Carrier Furnace Error Codes:
CARRIER FURNACE CODE CONTINUOUS OFF
Check 115VAC at L1 and L2
Check 24VAC at SEC-1 and SEC-2
CARRIER FURNACE CODE CONTINUOUS ON
Control has 24VAC power
CARRIER FURNACE CODE RAPID FLASHING
Line voltage (115VAC) polarity reversed
Refer to twinning kit instructions if twinned
CARRIER FURNACE CODE 1-1
No Previous Code
Stored status codes erased with power interruption or after 48 hours
CARRIER FURNACE CODE 1-2
Blower on After Power Up (115VAC or 24VAC)
Blower runs for 90 seconds if unit powered up during a call for heat (R-W closed)
CARRIER FURNACE CODE 1-3
Limit or Flame Roll-Out Switch Lockout
Control will auto-reset after 3 hours
Reset switch or replace fuse link
CARRIER FURNACE CODE 1-4
Control will auto-reset after three hours
CARRIER FURNACE CODE 2-1
Gas Heating Lockout
Control will not auto-reset
Check for mis-wired gas valve or defective control (Valve relay)
CARRIER FURNACE CODE 2-2
Abnormal Flame-Proving Signal
Flame proven while gas valve is de-energized
Inducer will run until fault cleared
Check for leaky gas valve or stuck open gas valve
CARRIER FURNACE CODE 2-3
Pressure Switch Did Not Open
Check for obstructed pressure switch or pressure switch stuck
CARRIER FURNACE CODE 2-4
Secondary Voltage Fuse is Open
Check for short circuit in secondary voltage (24VAC) wiring
CARRIER FURNACE CODE 3-1
Pressure, draft safeguard, aux-limit switch (when used) or blocked vent switch (when used) did not close or reopened (downflow only)
If open longer than five minutes, inducer shuts off for 15 minutes before retry
Check for various issues including proper vent sizing, restricted vent, defective pressure switch, etc.
CARRIER FURNACE CODE 3-3
Limit or flame roll-out switch is open
If open longer than 3 minutes, code changes to lockout #13
Check for various issues including dirty filter, loose blower wheel, inadequate combustion air supply, etc.
Flame roll-out switch requires manual reset or replace
CARRIER FURNACE CODE 3-4
Ignition Proving Failure
Control will try three more times before lockout #14 occurs
If flame signal lost during blower on-delay period, blower will come on for 90 second recycle delay
Check for various issues including control ground continuity, oxide buildup on flame sensor, gas valve turned off, etc.
CARRIER FURNACE YELLOW LIGHT
Signifies that the furnace is stuck in high-fire mode
High-fire mode should only operate briefly to heat a cold house quickly
If the yellow light stays on, it could mean that the furnace is stuck in high fire mode due to a faulty gas valve solenoid
Fix:Gas valve solenoid opens with an electric signal from the thermostat
It narrows its opening for low-fire mode and widens it for high-fire mode
If stuck in high-fire mode, the solenoid cannot be fixed and must be replaced
SOLID ORANGE LIGHT ON CARRIER FURNACE
This light means that there could be a buildup of dirt on the furnace burners that’s messing with the gas supply and heat production.
To fix it: If you’re seeing this light, it’s probably because there’s an incorrect balance of oxygen and gas in the furnace. It’s best to call in a pro to check it out and make sure everything is safe.
American Standard Furnace Troubleshooting
If you have an American Standard furnace, you may see error codes in the form of furnace flash codes. If the red LED light on the furnace is blinking steadily, it means the unit is operating normally. However, if the flashing is happening in a specific pattern, the number of flashes will give you an idea of what might be wrong. Here’s a breakdown of some common flash codes and what they mean:
7. American Standard Furnace Error Codes:
AMERICAN STANDARD FURNACE 2 FLASHES
This means the furnace is likely blowing cold air because it’s dropping the flame.
AMERICAN STANDARD FURNACE 3 FLASHES
This indicates a problem with the pressure switch.
AMERICAN STANDARD FURNACE 4 FLASHES
This indicates a problem with the limit switch.
AMERICAN STANDARD FURNACE 6 FLASHES
This indicates a problem with the polarity or grounding.
AMERICAN STANDARD FURNACE 7 FLASHES
This indicates a problem with the gas valve.
AMERICAN STANDARD FURNACE 9 FLASHES
This indicates a problem with the ignition or the ignitor circuit.
AMERICAN STANDARD FURNACE 22 FLASHES
This indicates a problem with the flame itself.
Bryant Furnace Troubleshooting
When your Bryant furnace is giving you trouble and isn’t working like it should, the flashing LED lights can help you figure out what’s going on. The LED lights flash in a certain pattern, with the short flashes indicating the first digit of the error code and the long flashes indicating the second digit. This two-digit code can give you a clue as to what’s wrong with your furnace.
8. Bryant Furnace Error Codes:
BRYANT FURNACE CODE RED LED1 ON
Furnace is operating in emergency heat.
BRYANT FURNACE CODE RED LED2 ON
The microprocessor has malfunctioned. To reset, put setup switch “SW-1” in the “on” position and jumper thermostat terminals “R”, “W/W1” and “Y/Y2” simultaneously with the door switch pushed in and power to the unit “on”. Disconnect jumper and place setup switch in the “off” position. If LED2 reappears, replace main control board.
BRYANT FURNACE CODE YELLOW LED3 ON
Furnace is operating in high heat.
BRYANT FURNACE CODE GREEN LED4 ON
Furnace is operating in low heat.
BRYANT FURNACE CODE RED LED2 FLASHING
Line voltage polarity is reversed.
BRYANT FURNACE CODE 1-1
No fault in recent history display.
Fix: Indicates no faults have occurred within the last five cycles. To read recent fault history, put setup switch “SW-1” in the “on” position. To clear recent fault history, put setup switch “SW-1” in the “on” position and jumper thermostat terminals “R”, “W/W1” and “Y/Y2” simultaneously until an “11” is flashed.
BRYANT FURNACE CODE 1-2
Blower calibration lockout.
Fix: Indicates RPM calculated for low heat was less than 250 RPM or greater than 1300 RPM on two successive attempts. Auto reset after three hours. Reset power and refer to fault #44 section.
BRYANT FURNACE CODE 1-3
Limit switch lockout.
Fix: Indicates the occurrence of 10 successive limit trips during high heat or three successive limit trips during low heat. Auto reset after three hours. Check for improper or misaligned limit and/or limit shield, improper high or low heat gas input adjustment, or stuck high heat solenoid in gas valve.
BRYANT FURNACE CODE 1-4
Fix: Control will auto-reset after three hours.
BRYANT FURNACE CODE 2-1
Invalid model selection.
Fix: Indicates model plug is missing or incorrect. See wiring diagram for correct connector jumper location.
BRYANT FURNACE CODE 2-2
Fix: Indicates setup switch “SW-1” or “SW-6” is positioned improperly. The following combinations will cause the fault: thermostat call with “SW-1” “on”, or thermostat call with “SW-6” “on”, or “SW-1” and “SW-6” both “on” together.
BRYANT FURNACE CODE 2-3
Invalid blower airflow selection.
Fix: Indicates improper “A/C” or “CF” switch setting. The 042 and 14 units can deliver 1-1/2 to 3-1/2 tons A/C and 600 to 1400 CFM for continuous fan. The 060 and 20 unit can deliver 2 to 5 tons A/C and 800 to 2000 CFM for continuous fan. If code is flashing, unit will default to the closest allowable airflow.
BRYANT FURNACE CODE 2-4
Secondary voltage fuse is open.
Fix: Check for short circuit in secondary voltage (24VAC) wiring.
BRYANT FURNACE CODE 3-1
Pressure switch did not close or reopened.
Fix: If open longer than five minutes, inducer shuts off for 15 minutes before retry. Check for excessive wind, proper vent sizing, defective inducer motor, low inducer voltage (115VAC), defective pressure switch, inadequate combustion air supply, restricted vent, disconnected or obstructed pressure tubing
Rheem Furnace Troubleshooting
Rheem furnaces come with a 7-segment diagnostic display that helps you figure out any issues with your heating system. Instead of flashing LED lights, the display gives you a code for easy diagnostics. For example, “0” means the unit is on standby and “H” means the heat is on. Here are the meanings of the other codes:
9. Rheem Furnace Error Codes:
RHEEM FURNACE ERROR CODE 10
There’s a one-hour lockout in place.
RHEEM FURNACE ERROR CODE 11
The ignition failed.
RHEEM FURNACE ERROR CODE 12
Low flame detected.
RHEEM FURNACE ERROR CODE 13
The flame was lost.
RHEEM FURNACE ERROR CODE 14
There was an unexpected flame.
RHEEM FURNACE ERROR CODE 20
There was a twinning fault.
RHEEM FURNACE ERROR CODE 22
Problem with high limit.
RHEEM FURNACE ERROR CODE 26
Reversal of line and neutral.
RHEEM FURNACE ERROR CODE 33
Roll-out switch problem.
RHEEM FURNACE ERROR CODE 55,57
Pressure switch issue.
RHEEM FURNACE ERROR CODE 58,59
Water or condensation problem.
RHEEM FURNACE ERROR CODE 61
Problem with the blower.
RHEEM FURNACE ERROR CODE 93
Problem with the control.
Ruud Furnace Troubleshooting
If you need assistance fixing your Ruud furnace, we’ve got you covered! Check out our quick guide on how to interpret the error codes on your model.
10. Ruud Furnace Error Codes:
RUUD FURNACE LED IS STEADILY ON
Normal fault detected.
RUUD FURNACE SINGLE LED FLASH
Failed to detect flame within three attempts for ignition, 1-hour lockout.
Fix: Reboot system.
RUUD FURNACE TWO LED FLASHES
The pressure switch is stuck open or induced draft blower problem detected.
Fix: Try to manually close the switch, replace the switch, or check blowers and vents for air pressure.
RUUD FURNACE THREE LED FLASHES
The limit switch is open, or the roll-out control is engaged.
Fix: Check for a restricted air vent, loose blower wheel, a defective blower, or a dirty air filter.
RUUD FURNACE FOUR LED FLASHES
The pressure switch is stuck closed, or the switch won’t open.
Fix: Check for an obstruction in the pressure tubing.
RUUD FURNACE SIX LED FLASHES
Line and Neutral are reversed.
Fix: Control board or the furnace’s ground could be defective.
If you are facing issues with your furnace, it is best to contact a professional furnace technician for a safe and reliable assessment and solution.
Furnace Error Codes As A Starting Point For Troubleshooting
In conclusion, understanding furnace error codes is essential in ensuring the smooth functioning of your heating system. Regular maintenance, checking for common issues, and troubleshooting with the help of this guide can help prevent potential problems from arising.
However, in case of a complex issue, it’s always best to seek the assistance of a professional technician for a safe and accurate resolution. Keeping the error codes in mind and following the tips mentioned in this guide can save you time, energy, and money in the long run.