Troubleshooting 4 Blinks on Furnace: A Quick Guide to Resolve LED Issues

If you have a gas furnace in your home, you may have noticed a small LED light on its control board that indicates its status and alerts you of any problems or errors. The light may blink in different patterns or colors to indicate various codes, depending on the model and manufacturer of your furnace.

If you notice 4 blinks on furnace, it’s essential to know what it means and how to fix it. This post will explain the error code, its causes, and how to fix it. We’ll also discuss your furnace’s high-limit and rollout switches and provide tips for avoiding future occurrences.

When you see four blinks on your furnace, the furnace has detected an open limit switch or a limit switch circuit failure. To prevent overheating, a furnace has two limit switches – the high-limit switch and the rollout switch – which act as safety devices. If the temperature of the furnace exceeds safe levels, the limit switches shut off the gas valve to prevent any potential danger. You can learn more about the types of furnace ignitors to improve your heating system efficiency.

The high-limit switch measures the air temperature in the furnace, and the rollout switch measures the flame temperature. If the temperature exceeds a limit, the switches cut off the gas supply to prevent overheating, damage, or fire. The switches are usually closed, allowing electricity to pass and keep the gas valve open. When they open, the circuit breaks and the gas valve closes, causing the furnace to stop heating and the LED light to blink four times.

If you find 4 Blinks on Furnace, it could be due to several reasons, such as:

  • A limit switch that is faulty or dirty causing it to open prematurely or not close properly.


  • An air filter that’s clogged or restricted reduces the airflow and causes the furnace to overheat.


  • A vent or flue that’s blocked or leaky prevents the exhaust gases from escaping and causing the furnace to overheat.


  • A heat exchanger that’s cracked or damaged allows flames to roll out and trigger the rollout switch.
  • A faulty or misaligned burner produces too large or hot flames and triggers the rollout switch.


  • A wire or connection that’s loose or broken causes a short circuit or open circuit in the limit switch circuit.

If you notice 4 Blinks on Furnace’s LED light of your Goodman furnace, you can follow these steps to troubleshoot and resolve the issue:

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1. You must turn off the power and gas supply to the furnace and wait a few minutes.

2. You Can Check the air filter and replace it if it is dirty or clogged.

3. Inspect the vent and the flue and clear any blockages or leaks.

4. Examine the heat exchanger and burners for any cracks, damage, or misalignment.

5. Check the limit switches and wires for any signs of wear, corrosion, or damage.

6. Reset the limit switches by pressing the small button on the side of the switch.

7. Turn on the power and gas supply to the furnace and observe the LED light.

8. If the light stops blinking and the furnace usually works, the problem is fixed.

If the light is still blinking, the problem persists, and you should contact a professional furnace technician for further assistance.

To prevent 4 Blinks on the Furnace in the future, you should follow these steps:

  • Change the air filter regularly and keep it clean.


  • Periodically inspect and clean both the vent and flue. Make sure they are not blocked or leaking.


  • Inspect and maintain the heat exchanger and burners periodically. Check for cracks, damage, or misalignment.


  • Regularly inspect and test the limit switches and wires to ensure they are not worn, corrupted, or damaged.


  • Hiring a professional furnace technician to service your furnace annually and check for any problems or errors is advisable.

High-limit and rollout switches are safety devices that monitor the temperature of the furnace. If the furnace overheats or the flames roll out, they shut off the gas valve to prevent mishaps. These switches are typically closed, allowing the electricity to flow through them, which keeps the gas valve open. However, in case of overheating or flames rolling out, they open up, breaking the circuit and closing the gas valve. When this happens, the furnace stops heating, and the LED light blinks four times.

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The high-limit switches are found near the heat exchanger and measure the temperature of the air that flows through the furnace. On the other hand, rollout switches are located near the burners and measure the temperature of the flames. Both switches have a small button on the side that can be pressed to reset after opening.

If your furnace has a green light instead of a red light, it may indicate a different code system. For example, some Carrier furnaces use a green light to indicate the status of the furnace and a red light to indicate error codes. In this case, a green light blinking 4 times means the furnace is in the soft lockout mode. This means the furnace has failed to ignite or stay lit thrice. The furnace will try to ignite again after an hour unless the problem is fixed.

Here are the steps to fix this problem:







Understanding the significance of a 4 Blinks on Furnace is crucial. This guide provides tailored troubleshooting steps for Goodman furnaces, addressing limit switches, airflow issues, and more. The manual also outlines proactive maintenance tips to prevent future problems. Detailed steps to resolve a soft lockout mode are provided for green-light furnaces. Follow these guidelines to ensure effective troubleshooting and long-term furnace efficiency.


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