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How to Troubleshoot Ruud Furnace Codes: Simple Guide

Ruud furnaces are known for their durability, energy efficiency, and superior comfort. However, like all mechanical appliances, they might occasionally face issues due to various reasons like wear and tear…

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Ruud furnaces are known for their durability, energy efficiency, and superior comfort. However, like all mechanical appliances, they might occasionally face issues due to various reasons like wear and tear or system malfunctions. 

To identify and troubleshoot these problems, Ruud furnaces come equipped with an LED diagnostic panel that displays specific error codes.

This guide will take you through a detailed journey on how to troubleshoot Ruud furnace codes, allowing you to maintain the efficiency and longevity of your furnace.

What are Ruud Furnace Codes?

Ruud furnace codes are a series of flashes that appear on the furnace’s LED diagnostic panel, generally located inside the furnace cabinet or on the blower compartment door. These codes flash in particular patterns to indicate normal operation or potential issues.

By understanding these codes, you can effectively troubleshoot your Ruud furnace, ensuring smooth and optimal operation.

How to Read Ruud Furnace Codes

Reading Ruud furnace codes primarily involves counting the number of LED flashes. Each flash count corresponds to a specific issue. Here’s a table that breaks down what each flash count means:

Flash CountCode Description
Two flashesSystem lockout (retry or recycle failure)
Three flashesPressure switch stuck open
Four flashesHigh limit switch open
Five flashesFlame sensed when no flame should be present
Six flashesPressure switch did not close or reopened
Seven flashesRollout switch open
Eight flashesIgnitor circuit failure
Nine flashesInternal control fault

Detailed Troubleshooting of Ruud Furnace Codes

Upon identifying the number of flashes and the corresponding code, you can embark on troubleshooting. Here’s an in-depth guide on how to address each furnace code:

Two flashes: System lockout (retry or recycle failure)

This code indicates an automatic reset failure. Try resetting the furnace by turning off the power for about a minute before turning it back on. If the issue persists, it might indicate a defective control board or a significant system issue, requiring professional assistance.

Three flashes: Pressure switch stuck open

This issue might be due to a blocked vent pipe, air intake pipe, or a cracked or clogged pressure switch hose. Inspect these areas and clear any obstructions, replace the hose if it’s damaged, and check if the pressure switch itself is faulty.

Four flashes: High limit switch open

This code suggests that the furnace is overheating. Causes could be a dirty or clogged air filter, improper duct size, a faulty blower motor, or restricted circulating airflow. Clean or replace the air filter, ensure the duct size matches your furnace’s capacity, and check for obstructions in the airflow.

Five flashes: Flame sensed when no flame should be present

This indicates a serious safety concern. The control board is detecting a flame when there should be none, possibly hinting at a gas valve leakage. This situation necessitates immediate professional help.

Six flashes: Pressure switch did not close or reopened

This code suggests there might be an issue with the pressure switch wiring or the pressure switch itself. It might also be a result of a malfunctioning inducer motor. Ensure the wiring is intact and consider replacing the pressure switch if necessary.

Seven flashes: Rollout switch open

The rollout switch is a safety device that prevents the furnace from operating if it detects flames or heat where they shouldn’t be. This could be due to blockages in the vents or heat exchanger. Cleaning these areas might help resolve the issue, but due to the serious nature of this code, you should also consider getting professional help.

Eight flashes: Ignitor circuit failure

This code could indicate an issue with the furnace’s ignitor. Check for loose or damaged wires, and if the ignitor is receiving current. If everything seems fine and the ignitor is not glowing, it’s probably faulty and needs to be replaced.

Nine flashes: Internal control fault

This code indicates a malfunction within the control board, potentially due to a faulty thermostat connection or a power supply issue. You might need to replace the control board if it’s defective.

READ: How to Troubleshoot Luxaire Furnace Codes Effortlessly


Understanding Ruud furnace codes can significantly simplify the troubleshooting process and keep your furnace running efficiently. While some issues can be resolved at home, others might require the expertise of a professional. Always adhere to safety measures and turn off the power supply before attempting to fix any issues.

We hope this comprehensive guide has empowered you with the necessary knowledge to troubleshoot Ruud furnace codes effectively.

I'm an HVAC enthusiast and a passionate writer dedicated to sharing valuable insights and practical tips about heating, cooling, ventilation, and air conditioning systems.

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Hi there, I'm Robert Brooks

Hi there, I'm Robert Brooks

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