Rheem Furnace Code 59 signals a specific fault condition in many Rheem gas furnaces that affects operation and safety. This article explains what Code 59 means, how to diagnose common causes, step-by-step troubleshooting guidance, likely repairs and costs, and when to call a licensed HVAC technician. The guidance is tailored for U.S. homeowners seeking practical, reliable information to resolve or understand this error code.
| Item | Quick Summary |
|---|---|
| Code | 59 |
| Primary Meaning | Ignition or Flame Detection Fault / Safety Lockout |
| Common Causes | Dirty flame sensor, faulty ignitor, gas supply issue, control board or wiring failure |
| DIY Likelihood | Moderate for sensor cleaning, low for component replacement |
| When To Call Pro | After simple checks, or anytime gas components are suspected |
What Rheem Furnace Code 59 Means
Rheem Furnace Code 59 typically indicates a problem related to ignition or flame detection that results in a safety lockout. The furnace control board either failed to detect a consistent flame during the ignition sequence or registered an irregular flame signal. This is a safety response to prevent unburned gas accumulation or unsafe operation.
How Rheem Locates And Reports Faults
Rheem furnaces use a control board with diagnostic LEDs or a status display that flashes error codes. Code 59 corresponds to a specific diagnostic entry in the furnace manual. The control board monitors ignition sequence timing, flame sensor input, and gas valve operation to decide when to lock out and display this code.
Common Causes Of Code 59
Dirty Or Failing Flame Sensor: Grease and oxidation can prevent the sensor from detecting flame current, triggering lockout.
Faulty Ignitor: A cracked or weakened hot surface ignitor may not reliably light the gas, causing repetitive ignition failures.
Gas Supply Problems: Low gas pressure, a closed gas valve, or interrupted gas service can stop ignition.
Control Board Or Wiring Issues: Faulty relays, damaged connectors, or corroded terminals may cause false signals or missed flame detection.
Ventilation Or Combustion Air Problems: Blocked flues or insufficient combustion air can create abnormal flame behavior and trigger safety routines.
Safety First: Precautions Before Troubleshooting
Working around gas and electrical components involves risk. Before any inspection, turn off power to the furnace at the breaker and shut off the gas if instructed by the manual. If smelling gas, evacuate the area and call the gas utility or emergency services immediately. If unsure, contact a licensed HVAC technician.
Step-By-Step DIY Troubleshooting
1. Reset The Furnace
Locate the furnace power switch or circuit breaker and turn it off for 30 seconds, then restore power. Some lockouts clear after a reset and may allow one retry of the ignition sequence. Observe the furnace behavior and whether Code 59 returns.
2. Inspect Error Code History
Check the control board LED or display for persistent or multiple codes. Some Rheem units keep a diagnostic history useful for pinpointing intermittent issues. Record any additional codes and patterns.
3. Clean The Flame Sensor
Many Code 59 faults are resolved by cleaning the flame sensor. After turning off power and gas, access the sensor—usually a slim metal rod near the burner—and gently clean it with fine-grit sandpaper or steel wool until bright. Reinstall and test. This job is low-cost and often effective.
4. Inspect The Ignitor
Visually inspect the hot surface ignitor for cracks or discoloration. Do not touch ceramic elements with bare hands. If the ignitor is visibly damaged, replacement is required. Ignitor tests with a multimeter may show an open circuit if failed.
5. Check Gas Supply
Confirm other gas appliances are working. Verify the furnace gas shutoff valve is open. If gas service is suspect, contact the gas utility. Never attempt to repair gas piping unless certified.
6. Examine Wiring And Connections
Inspect wiring to the flame sensor, ignitor, and control board for loose connections, frayed insulation, or corrosion. Secure connectors and replace any damaged wires. Small wiring issues can cause intermittent Code 59 faults.
7. Verify Venting And Combustion Air
Ensure intake and exhaust vents are clear of debris, bird nests, or ice. Blocked venting can starve combustion air and cause irregular flames, leading to lockouts. Clear obstructions carefully.
When A Professional Technician Is Needed
Call a licensed HVAC technician if cleaning the sensor and basic checks do not clear Code 59. Professional diagnostics are needed for component replacement, control board faults, gas pressure testing, or complex wiring issues. Technicians have the tools and training to perform safe gas valve and pressure adjustments.
Typical Repairs And Estimated Costs
Costs vary by region and system, but these ballparks help set expectations. Prices reflect U.S. residential service averages and include parts and labor.
| Repair | Typical Cost Range |
|---|---|
| Flame Sensor Cleaning | $0–$100 If DIY Or $75–$200 Service Call + Labor |
| Flame Sensor Replacement | $100–$250 |
| Ignitor Replacement | $150–$400 |
| Control Board Repair/Replace | $300–$800 |
| Gas Valve Service | $200–$600 |
Parts, Tools, And Materials Commonly Required
Basic tools for homeowner-level troubleshooting include a multimeter, nut drivers, screwdrivers, fine sandpaper or emery cloth for sensor cleaning, and a flashlight. Replacement parts such as flame sensors and ignitors are model-specific—use the Rheem furnace model number to order correct parts.
Preventive Maintenance To Avoid Code 59
Annual Professional Tune-Up: A yearly service visit that includes burner cleaning, flame sensor inspection, and system checks reduces ignition and detection failures.
Regular Filter Changes: Replace HVAC filters per manufacturer guidance to maintain airflow and combustion performance.
Keep Vents Clear: Maintain clear intake and exhaust pathways to ensure proper combustion air and venting.
Prompt Repairs: Address small faults early to prevent escalation into control board or gas valve damage.
Model-Specific Variations And Manuals
Different Rheem models may document Code 59 differently or include model-specific diagnostic steps. Homeowners should locate their furnace model number on the data plate and consult the Rheem installation and service manual or Rheem’s technical support for exact definitions and recommended procedures.
How To Report To A Technician
When calling a technician, provide the furnace model and serial number, describe the sequence of events, list any additional error codes, and report actions already taken such as sensor cleaning or resets. This information speeds diagnosis and helps the technician bring proper parts.
Common Misdiagnoses And How To Avoid Them
Ignoring flame sensor issues and replacing expensive parts without testing is a common mistake. Similarly, assuming a single-code meaning without checking for related faults can waste time. Follow a systematic diagnostic order: reset, inspect sensors and ignitor, verify gas, then escalate to electronics.
Frequently Asked Questions
Is It Safe To Run The Furnace After Seeing Code 59?
No. Code 59 indicates a safety lockout. Running the furnace without addressing the cause risks repeated lockouts or unsafe operation. Perform recommended checks or contact a technician.
How Long Will Cleaning The Flame Sensor Take?
Cleaning the flame sensor takes about 15–30 minutes for a homeowner comfortable with basic tools. Ensure power is off and follow safety precautions.
Can Cold Weather Cause Code 59?
Cold conditions can cause venting obstructions like ice or create ignition stress on components, which may contribute to Code 59. Confirm venting is clear and the furnace has proper clearance.
Will Resetting The Furnace Fix It Permanently?
Resetting clears lockout temporarily but does not address the underlying cause. If Code 59 returns, follow troubleshooting steps or call a professional.
Additional Resources And References
Consult the Rheem owner’s manual and technical bulletins for model-specific diagnostic tables and error-code descriptions. Government and industry resources on HVAC safety provide guidance on gas appliance precautions. For parts lookup, use Rheem’s official parts diagrams or authorized distributors.
Key Takeaways
Rheem Furnace Code 59 commonly points to flame detection or ignition faults with multiple potential causes. Simple actions—resetting, cleaning the flame sensor, checking gas supply, and inspecting wiring—resolve many issues. For component replacements, gas issues, or persistent faults, enlist a licensed HVAC technician to ensure safe, effective repairs.