Rheem Furnace Error Code 59: Causes, Diagnosis, and Fixes

The Rheem Furnace Error Code 59 indicates a specific operational fault that requires targeted diagnosis to restore safe heating. This article explains what the code means, common causes, step-by-step troubleshooting, and when to contact a professional, providing practical and safe guidance for homeowners and technicians.

Item	Quick Summary
Error Code	59
General Meaning	Gas valve or burner ignition related fault requiring inspection
Common Causes	Ignition failure, gas supply issues, valve defect, control board problem, flame sense issues
Recommended Action	Check vents, power reset, inspect gas supply, examine ignition components, call certified HVAC tech if unresolved

What Rheem Furnace Error Code 59 Means

Rheem furnaces use diagnostic codes to indicate specific faults. Error Code 59 commonly points to problems related to the ignition sequence or gas valve operation. The control board has detected a failure to establish or maintain proper combustion within expected parameters during startup or operation.

How Rheem Diagnostic Codes Work

Rheem control boards monitor sensors, ignition devices, gas valves, and flame sensing circuits. When a safety limit or expected signal is not met, the board logs an error code and may lock out the furnace to prevent unsafe operation.

Common Causes Of Error Code 59

Error Code 59 can stem from multiple components and conditions. Typical causes include:

• Ignition Failure: A faulty hot surface ignitor (HSI) or intermittent spark ignition can prevent burner light-off.
• Gas Supply Issues: Closed gas valves, low pressure, or a fuel supply interruption can result in ignition attempts failing.
• Gas Valve Or Solenoid Fault: Malfunctioning gas valve or pilot gas control solenoid can prevent gas flow to burners.
• Flame Sensing Problems: A dirty or misaligned flame sensor may not detect flame presence, causing the furnace to shut down.
• Control Board Or Wiring Faults: Damaged wiring, loose connectors, or a defective control board can create false error reports.
• Blocked Venting Or Combustion Air: Restricted intake or exhaust can cause abnormal combustion and trigger a lockout.

Safety First: Precautions Before Troubleshooting

Working on gas-fired equipment carries risk. Turn off power and gas before inspecting internal components. If the homeowner smells natural gas, evacuate the home and call the gas utility or emergency services. When in doubt, contact a licensed HVAC technician.

Step-By-Step Troubleshooting Guide

1. Note Furnace Behavior And Reset

Record the sequence of lights, fan behavior, and whether the flame attempts to ignite. Perform a power reset by switching the thermostat to Off, turning off the furnace power switch, waiting 60 seconds, then restoring power. Some lockouts clear after reset and one restart.

2. Check Basic External Conditions

Verify the gas supply is on at the meter and at the shutoff near the furnace. Confirm the thermostat is calling for heat and set appropriately. Inspect vents and intake for blockages, nests, or debris.

3. Inspect Ignition Components

For furnaces with a hot surface ignitor, visually inspect for cracks or discoloration; a fractured HSI will not glow properly. For spark ignition systems, listen for sparking and inspect electrode condition and gap. Replace visibly damaged ignitors or electrodes.

4. Test Flame Sensor

Locate the flame sensor and remove accumulated soot or oxidation using fine steel wool or emery cloth. Reinstall securely. A weak flame signal often causes the control board to log a lockout.

5. Examine Gas Valve Operation

With power on and a call for heat, observe whether the gas valve attempts to open. A multimeter can check for control voltage from the board to the valve. No voltage indicates a control or wiring issue; voltage present with no gas flow suggests a faulty valve or fuel supply issue.

6. Inspect Wiring And Connectors

Check harness connectors to the control board, ignition module, flame sensor, and gas valve for loose pins or corrosion. Repairing or replacing damaged wiring can resolve intermittent errors.

7. Look For Control Board Faults

Control boards can fail due to age or electrical surges. Burnt components, bulging capacitors, or water damage indicate the board may need replacement. Compare error behavior against Rheem troubleshooting charts for confirmation.

When To Call A Professional

If basic checks (power reset, cleared flame sensor, visible ignitor replacement) do not clear Error Code 59, contact a licensed HVAC technician. Call a pro when gas valve testing, control board diagnostics, or sealed combustion system checks are required.

Typical Parts That May Need Replacement

Frequently replaced components associated with Error Code 59 include the hot surface ignitor, flame sensor, gas valve assembly, ignition module, and the control board. Costs vary by model and labor rates.

Component	Estimated Parts Cost	Notes
Hot Surface Ignitor	$40–$120	Common DIY replacement if accessible
Flame Sensor	$15–$60	Often cleaned; replacement inexpensive
Gas Valve	$150–$400	Higher cost; requires certified technician
Control Board	$150–$500	Diagnostic recommended before replacement

Estimated Labor And Repair Timeline

Minor fixes like cleaning a flame sensor or replacing an ignitor can be completed in under an hour by a technician. Complex gas valve or control board replacements often take 1–3 hours including testing and safety checks. Obtain an itemized estimate before work begins.

Preventive Maintenance To Reduce Recurrence

Regular furnace maintenance reduces the risk of error codes. Recommended actions include annual professional tune-ups, changing air filters every 1–3 months, ensuring proper ventilation, and keeping the furnace area clean.

Model Variations And Manufacturer Guidance

Rheem models can differ in diagnostic behavior. Always consult the specific unit’s installation and service manual for the exact meaning of Error Code 59 on that model. Rheem tech literature and authorized dealer support provide model-specific troubleshooting steps.

Cost-Benefit Considerations For Repairs

When deciding on repairs, compare the cost of parts and labor to the furnace’s remaining expected life. For older systems with multiple failing components, replacement may provide better long-term value and efficiency.

Frequently Asked Questions (FAQs)

Can A Dirty Air Filter Cause Error Code 59?

A dirty filter can restrict airflow and contribute to combustion abnormalities, but it is not the most common direct cause of Error Code 59. Still, maintaining clean filters helps overall system performance.

Is It Safe To Keep Restarting The Furnace After Error 59?

Repeated restarts are not recommended. The control board locks out for safety reasons. Repeated attempts without diagnosing the root cause may worsen damage or create unsafe conditions.

Will A Circuit Breaker Trip Cause This Error?

A tripped breaker can interrupt ignition components and cause error logging, but typically the board will report a general power loss rather than a specific 59 code. Verify uninterrupted power during diagnostics.

How Long Will A Technician Take To Diagnose The Problem?

Initial diagnosis can often be completed within 30–90 minutes depending on access and the need for specialized instruments. Full repair time varies with the required parts and complexity.

Useful Resources And Where To Find Parts

Genuine Rheem replacement parts are available through authorized dealers and HVAC distributors. Manufacturer manuals, Rheem service bulletins, and technician forums provide helpful diagnostics. Always use parts rated for the specific model to maintain safety and warranty.

Final Practical Tips

• Keep a maintenance log with dates of filter changes and service visits.
• Take photos of wiring and connectors before disassembly for correct reassembly.
• If uncertain about gas or electrical work, hire a licensed technician to avoid safety risks.

Addressing Rheem Furnace Error Code 59 begins with safe, methodical checks and escalates to professional diagnostics when component-level testing is required. Following the steps above helps homeowners and technicians identify likely causes and make informed repair decisions.