Estimated reading time: 4 minutes
Scene: Your heating and cooling system is not responding to the thermostat. Before you call the HVAC Tech for serivce, you may be able to help them kick start the diagnosis by reading a sequence of blinking lights on the appliance.
Most of the furnaces in our area are Goodman and have a small red, green, or yellow LED status light on the furnace board. The light blinks when the furnace needs service. The sequence can spell out error codes and are diagnostic tools that help indicate specific issues or potential problems within the furnace system.

The codes and their meanings are often found on a label inside the furnace panel. They function similarly across many brands, however, the exact sequences may vary between manufacturers.
On Goodman furnaces, the blinks represent a two-digit code.
You’ll see the flashing or blinking patterns through the viewing port on the front of the furnace, or when you open the furnace door that holds the viewing port (usually the bottom door), you’ll see the light on the circuit board. For example, a sequence of three short blinks followed by one long blink could indicate an error code 31.

The meaning of each code is outlined in the furnace’s manual or on the label affixed to the back of the “Top” furnace door.
Common issues might include problems with the furnace’s pressure switch, flame sensor, ignition, or a high-limit switch.
Those terms can be handy when consulting an HVAC professional for service or maintenance.
NOTE: Most furnaces have two doors – Top and Bottom. Let the HVAC Tech open the door with the viewing port unless you know how a furnace operates. The door with the viewing port is usually the “Bottom” door.
Similarities Across Brands
Most furnace brands employ similar LED blinking sequences, with slight differences in the number of blinks or the specific interpretations.
Goodman, Carrier, Trane, and Lennox all use this type of system, but each may have unique codes. For instance, where a Goodman furnace might use a blinking pattern to indicate a pressure switch issue, another brand might use a single continuous blink.
To correctly diagnose an issue:
- Access the furnace panel and locate the error code chart.
- Count the blinks and note whether they are short or long.
- Refer to the chart for the specific meaning of the code.
Here’s a spreadsheet-style list of common error codes and their meanings. These codes apply broadly to Goodman furnaces and is not an exhaustive list.
Blinking Sequence | Error Code | Issue/Description | Possible Causes |
---|---|---|---|
1 Blink | 1 | System Lockout – No Ignition | Dirty flame sensor, faulty ignitor, or gas valve issue |
2 Blinks | 2 | Pressure Switch Stuck Open | Blocked vent, faulty pressure switch, or disconnected tubing |
3 Blinks | 3 | Pressure Switch Stuck Closed | Shorted switch, blocked exhaust, or improper vent installation |
4 Blinks | 4 | Open High-Limit Switch | Overheating due to restricted airflow (dirty filter, blocked vents) |
5 Blinks | 5 | Flame Sensed Without Ignition | The system running as expected |
6 Blinks | 6 | Open Rollout Switch | Flame rollout caused by restricted venting, heat exchanger issues |
7 Blinks | 7 | Faulty Ignitor Circuit | Broken or disconnected ignitor |
8 Blinks | 8 | Low Flame Sense Signal | Dirty flame sensor, weak gas flow, or improper grounding |
Continuous Fast Blinking | Rapid Blinks | Reversed Polarity Detected | Line and neutral wiring reversed |
Steady On (No Blinks) | Steady Light | Normal Operation (No Faults) | Regular Operation (No Faults) |
Notes:
- System Lockout (Code 1): The system enters lockout after three failed attempts to ignite. You may need to reset the furnace by turning off the power for 30 seconds.
- Pressure Switch Errors (Codes 2 and 3): These switches monitor airflow. Blockages in the flue pipe or intake can cause these errors.
- High-Limit and Rollout Switches (Codes 4 and 6): These codes can signal the system may be overheating. Investigate airflow or combustion issues.
- Flame Sensor Issues (Codes 5 and 8): Clean the flame sensor with fine-grit sandpaper or replace it if faulty.
Consulting the manufacturer’s website or a professional is recommended if you can’t access the label or manual. Keep in mind that while these codes give a helpful starting point for diagnosing problems, they often require further troubleshooting by a licensed technician for repairs.
⚠️ Information in this article is intended for educational purposes only. Any work related to the topics in this video should be performed by licensed technicians or by apprentices under the supervision of licensed technicians. I am not responsible for any possible damages or injuries caused by using or misusing any information provided.
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