Janitrol Furnace Pilot Light Troubleshooting and Repair Guide

The Janitrol furnace pilot light is a small but critical component that keeps older gas furnaces running reliably. This guide explains how the pilot light system works, common problems, step-by-step troubleshooting, safe relighting procedures, component testing, and guidance on repair or replacement. The information helps homeowners determine when a simple fix is possible and when to call a qualified HVAC technician.

Issue	Likely Cause	Quick Action
Pilot Won’t Stay Lit	Faulty thermocouple or draft	Inspect flame, clean pilot, test thermocouple
No Pilot Flame	Gas valve off or clogged pilot orifice	Check gas supply, clean or replace orifice
Weak Yellow Flame	Dirty pilot tube or low gas pressure	Clean tube, check gas pressure
Intermittent Operation	Loose wiring or failing gas valve	Inspect wiring, call pro for valve

How The Janitrol Furnace Pilot Light System Works

The pilot light on Janitrol furnaces serves as a constant ignition source for the main burner. Older Janitrol units use a standing pilot with a pilot orifice, pilot tube, thermocouple and a gas control valve with a pilot setting. When the pilot flame heats the thermocouple, it generates a small voltage that holds the gas valve open. If the flame goes out, the thermocouple cools and the gas valve closes, preventing unburned gas buildup.

Common Pilot Light Problems And What They Mean

Recognizing common symptoms helps narrow down causes quickly. A pilot that won’t stay lit often points to a weak or failing thermocouple, a dirty pilot assembly, or drafts blowing the flame away. A pilot that won’t light at all can indicate a closed gas valve, clogged pilot orifice, or a failed igniter on models with electronic ignition. A yellow or flickering flame suggests contamination or improper gas pressure.

Safety Precautions Before Working On A Janitrol Pilot

Working safely around gas appliances is essential. Always shut off the gas supply at the appliance or main gas shutoff before attempting inspection or maintenance. Ensure adequate ventilation and avoid open flames while checking for gas leaks. If any gas odor is detected, evacuate the area and contact the gas utility or a licensed technician immediately. Only qualified users comfortable with gas systems should perform pilot relighting and adjustments.

Step-By-Step: How To Relight A Janitrol Furnace Pilot

Relighting procedures vary slightly by model but the general steps below apply to standing pilot Janitrol furnaces. Refer to the furnace data plate and manual for model-specific instructions.

1. Turn Off The Gas And Power: Move the gas control knob to “Off” and wait at least five minutes for any residual gas to clear.

2. Access The Pilot Assembly: Open the furnace access panel to expose the pilot light assembly and burner area.

3. Set Gas Valve To Pilot: Turn the gas control knob to the “Pilot” position and depress it to allow gas to the pilot orifice.

4. Ignite The Pilot: Use the furnace’s piezo igniter button if present, or use a long match/lighter to ignite the pilot while holding the gas control knob depressed.

5. Hold And Observe: Continue holding the gas control knob for 30–60 seconds after ignition to allow the thermocouple to heat.

6. Release And Monitor: Release the knob. If the pilot remains lit, switch the gas control to “On.” Run several furnace cycles to confirm stable operation.

Cleaning The Pilot Orifice And Tube

Clogging from dust, spider webs or combustion deposits commonly reduces pilot flame size. Cleaning can restore reliable ignition.

• Turn Off Gas And Power Before Starting.

• Use Compressed Air Or A Thin Wire To Gently Clear The Pilot Orifice; Avoid Enlarging The Orifice.

• Blow Out The Pilot Tube And Surrounding Areas To Remove Debris.

• Wipe Accessible Surfaces With A Clean Cloth; Reassemble And Test.

Testing And Replacing The Thermocouple

The thermocouple is the most frequent cause of a pilot that will not stay lit. Testing is straightforward with a multimeter.

1. Disconnect The Thermocouple From The Gas Valve.

2. Heat The Thermocouple Tip With A Lighter Until Red Hot.

3. Measure Millivolts At The Thermocouple Terminal; A Healthy Unit Produces About 25–40 Millivolts.

4. If Output Is Low Or Zero, Replace The Thermocouple With The Correct Janitrol-Specified Part.

When The Pilot Flame Is Weak Or Yellow

A healthy pilot flame is predominantly blue with a stable inner cone. A weak, mostly yellow flame indicates incomplete combustion due to contamination, low gas pressure, or incorrect orifice size.

Cleaning the pilot assembly often resolves the issue. If the flame remains yellow after cleaning, the furnace may have incorrect gas pressure or a problem with the gas regulator; a licensed HVAC or gas technician should diagnose and correct pressure-related issues.

Electronic Ignition Variants And Troubleshooting

Some later Janitrol models use hot surface igniters or intermittent pilot systems rather than a standing pilot. These systems have different failure modes—failed igniters, flame sensors, or control module faults.

For electronic systems, check for visible damage to the igniter, inspect wiring and connectors for corrosion, and verify that the control board is receiving power and sending proper signals. Flame sensors can be cleaned with light abrasive to improve sensing ability. Electronic diagnostics often require specialized meters or the manufacturer’s error codes.

Gas Valve And Control Problems

The gas control valve regulates pilot and main burner gas flow. Symptoms of a failing valve include inability to reach “On” position, clicking without ignition, or intermittent gas supply. Valves can stick from corrosion or internal debris.

It is not recommended to attempt internal valve repair except by a certified technician. Replacement of the gas control assembly should use OEM or equivalent parts and follow local codes.

Wiring, Switches, And Safety Interlocks

Pilot and ignition systems interface with limit switches, thermostats, and flame rollout switches. A tripped limit switch or faulty high-limit can prevent the pilot or main burner from operating.

Visually inspect wiring for loose connections, corrosion, or broken insulation. Use care when testing low-voltage circuits, and ensure the thermostat calls for heat during troubleshooting to confirm the control path.

Parts And Compatibility For Janitrol Furnaces

Using the correct parts is essential for safety and performance. Thermocouples, pilot orifices, gas valves and pilot assemblies should match the furnace model specifications. Janitrol furnaces were produced under several model families; cross-referencing the model number and the data plate is crucial when ordering parts.

OEM parts ensure compatibility with gas pressure settings, thread sizes, and mounting arrangements. When OEM parts are unavailable, consult a licensed supplier for compatible aftermarket parts with matching specs.

When To Call A Professional

Call a licensed HVAC or gas technician if any of the following apply: inability to maintain a pilot after basic cleaning and thermocouple replacement, suspected gas leaks, faulty gas valve, problems with gas pressure or regulator, electronic control faults, or unfamiliarity with gas appliance safety procedures. Professional service protects against hazards and ensures work meets local codes.

Maintenance Tips To Prevent Pilot Problems

• Schedule Annual Furnace Inspection And Cleaning To Reduce Debris Buildup.

• Keep The Furnace Area Clear Of Dust And Debris To Minimize Pilot Contamination.

• Check For Pests Or Spiders Near The Pilot; Use Mesh Screens Where Permitted.

• Operate The Furnace Briefly During Shoulder Seasons To Keep Components Functional.

• Replace Aging Thermocouples As A Preventive Measure If Pilot Issues Recur.

Cost Estimates For Janitrol Pilot Repairs And Parts

Costs vary by region and whether the job is DIY or professional. Typical parts and service ballpark estimates:

Item	Estimated Cost Range
Thermocouple	$15 – $60
Pilot Orifice/Cleaning	$0 – $100 (DIY to pro service)
Gas Control Valve	$150 – $450 plus labor
Professional Diagnostic & Repair	$100 – $300 (depending on diagnosis and parts)

Troubleshooting Checklist For Homeowners

• Confirm Gas Supply: Verify the home gas supply is on and other gas appliances operate.

• Inspect Flame: Look for a stable blue pilot flame with a sharp inner cone.

• Clean Pilot Assembly: Remove debris from the orifice and tube.

• Test Thermocouple: Measure millivolts or replace if suspected faulty.

• Check For Drafts: Seal gaps that may blow out the pilot flame.

• Observe Furnace Controls: Ensure limit switches, thermostat and wiring are intact.

Resources And Where To Find Parts

Parts can be sourced from HVAC supply houses, authorized Janitrol parts distributors, or reputable online retailers specializing in furnace components. Always match the furnace model number and part specifications. Manufacturer manuals and HVAC forums provide model-specific diagrams and practical tips, but owners should prioritize official documentation and certified technicians for complex repairs.

Key Takeaways For Janitrol Furnace Pilot Light Care

Regular maintenance, correct replacement parts, and adherence to safety procedures are the best defenses against pilot light problems on Janitrol furnaces. Many pilot issues are resolved by cleaning and thermocouple replacement, but gas valve failures, gas pressure issues, and electronic ignition faults require professional diagnosis. When in doubt, contact a licensed HVAC technician to ensure safe and code-compliant repairs.