Coleman Evcon Furnace Troubleshooting Guide

The Coleman Evcon furnace troubleshooting guide provides practical steps to diagnose common heating problems, interpret error codes, and perform basic repairs safely. This article helps homeowners identify issues, understand diagnostic lights and switches, and decide when to call a professional technician.

Problem	Likely Cause	Quick Action
No Heat	Thermostat, pilot/ignition, power	Check thermostat, power, reset
Weak Heat	Clogged filter, dirty burners, blower	Replace filter, clean vents
Short Cycling	Flame sensor, limit switch, oversized unit	Inspect sensors, clear airflow
Ignition Failure	Blocked pilot, faulty igniter	Clean pilot, test igniter

How Coleman Evcon Furnaces Work

Coleman Evcon furnaces operate using a gas burner, heat exchanger, and blower to deliver warm air through ductwork. Modern models use electronic ignition and control boards to manage startup, flame sensing, and safety features.

Understanding the basic sequence—thermostat call, inducer motor, ignition, burner operation, blower on—helps isolate where failures occur. Safety interlocks such as limit switches and pressure switches protect the system from dangerous conditions.

Safety First: Precautions Before Troubleshooting

Turn off power at the furnace switch and the breaker before accessing internal components. Shut off the gas supply if working on burners or ignition systems.

Use a multimeter rated for household voltage to test electrical components, and wear gloves and eye protection. If a gas smell is present, evacuate the home and call the gas company or emergency services immediately.

Tools And Parts Needed

• Multimeter (voltage, continuity)
• Screwdrivers and nut drivers
• Replacement air filters
• Soft brush and vacuum for cleaning
• Thermostat batteries or replacement thermostat
• Manufacturer manual or wiring diagram

Initial Checks For Any Coleman Evcon Furnace Problem

Start with these basic checks to quickly resolve many common issues.

• Verify thermostat settings: mode set to heat and temperature above room temperature.
• Check circuit breaker and furnace switch; reset if tripped.
• Replace or clean air filter; clogged filters reduce airflow and efficiency.
• Inspect vents and registers for obstructions and ensure dampers are open.

Interpreting Diagnostic Lights And Error Codes

Many Coleman Evcon furnaces include a status LED on the control board that flashes error codes. Count the flashes and reference the furnace manual for exact meanings.

Common LED patterns: one flash often indicates normal operation, two or three flashes may indicate pressure switch or flame failure, and continuous rapid flashing can point to lockout. Consult the model-specific code chart for precise diagnostics.

No Heat: Step-By-Step Troubleshooting

If the furnace does not produce heat, follow a systematic approach to find the cause.

1. Confirm thermostat call for heat and correct wiring connections.
2. Check furnace power: ensure the switch is on and breaker not tripped.
3. Inspect the pilot or electronic ignition: for standing pilot systems, ensure pilot flame is steady; for electronic ignitions, listen for the spark or hot surface igniter operation.
4. Examine the gas valve: verify gas supply is on; if suspected faulty, contact a technician.
5. Look at the control board for error codes and reset per manual if safe.

Ignition And Pilot Problems

Pilot flame problems or failed igniters are common on older Coleman Evcon units. A weak pilot, dirty thermocouple, or failed hot surface igniter can prevent ignition.

For pilot systems, clean the pilot orifice and replace the thermocouple if it shows poor millivolt output. For electronic ignition, test the igniter for continuity and visible damage; hot surface igniters are fragile and require replacement when cracked.

Flame Failure Or Lockout

Flame failure occurs when the system detects no flame during a call for heat. This can be caused by a dirty flame sensor, gas supply interruption, or a malfunctioning control board.

Cleaning the flame sensor with fine abrasive or emery cloth often restores reliable sensing. Ensure the flame makes proper contact with the sensor and that the sensor’s wiring is secure.

Short Cycling And Overheating

Short cycling—frequent on-off cycles—reduces efficiency and stresses components. Common causes include clogged filters, blocked return vents, failing blower motors, and faulty limit switches.

Inspect and replace the air filter first. Check the blower wheel for debris and ensure the heat exchanger and vents are clear. If the high-limit switch trips, examine airflow and suspect a failing switch if airflow is adequate.

Poor Airflow And Weak Heat Output

Poor airflow reduces heat delivery and can cause the furnace to overwork. Typical causes are dirty filters, closed supply registers, duct leaks, or a failing blower motor.

Replace filters regularly, inspect ducts for disconnections or leaks, and check the blower motor capacitor if the blower struggles to start. Sealing duct leaks can improve heating performance and energy efficiency.

Unusual Noises And Vibrations

Banging, rattling, or squealing noises point to mechanical issues. Banging during startup often indicates delayed ignition or a dirty burner.

Squealing or grinding typically signals worn blower bearings or a failing belt on older designs. Tighten loose panels and fasteners to remove rattles, and lubricate motors if applicable.

Condensate Drain Issues (For High-Efficiency Models)

High-efficiency Coleman Evcon furnaces produce condensate that drains through a PVC line. Clogs in the condensate trap or drain can trigger pressure switch errors and shutdowns.

Flush the drain with warm water and a mild bleach solution to remove biological growth. Ensure the trap is filled and the condensate pump (if present) operates correctly.

Pressure Switch And Venting Problems

Pressure switches confirm inducer motor and vent operation. A blocked vent, cracked inducer motor housing, or failed switch can prevent furnace startup.

Inspect vent terminations for debris or nests and ensure the inducer motor runs during startup. Test the pressure switch tubing for blockages and verify proper vacuum with a manometer or multimeter continuity test during inducer operation.

Control Board And Wiring Diagnostics

A failing control board or loose wiring can create intermittent problems. Visually inspect the board for burn marks, swollen capacitors, or loose connectors.

Use a multimeter to verify 24V thermostat power and signals. Replace the control board only after verifying other systems, as boards are costly and often not the root cause.

When To Replace Parts Versus Call A Professional

Homeowners can replace air filters, clean flame sensors, and clear vents safely. Replace accessible components like standard igniters or capacitors if comfortable with basic electrical work.

Call a licensed HVAC technician for gas valve replacement, heat exchanger cracks, control board swaps, complex wiring, or persistent combustion issues. Professional service ensures safety and proper gas handling.

Maintenance Tips To Prevent Future Problems

• Replace air filters every 1–3 months depending on use and filter type.
• Schedule annual professional tune-ups before the heating season.
• Keep vents and returns clear and inspect ductwork annually.
• Clean burners and flame sensors during scheduled maintenance visits.
• Test carbon monoxide detectors and replace batteries regularly.

Parts And Manuals: Finding The Right Resources

Locate the furnace model number on the unit’s data plate to find accurate parts and wiring diagrams. Manufacturer manuals and parts lists are often available online from Coleman, Evcon, or authorized parts distributors.

Use OEM replacement parts to ensure compatibility and reliability. Aftermarket parts may fit but can lead to performance issues or void warranties.

Common Model-Specific Issues

Older Coleman Evcon units with standing pilot systems often face thermocouple and pilot orifice problems, while newer electronic ignition models may show more control board and pressure switch issues.

High-efficiency condensing models require attention to condensate drains and PVC venting. Knowing the model type guides targeted troubleshooting steps.

Frequently Asked Questions

How Can One Reset A Coleman Evcon Furnace?

Reset by turning the thermostat off, switching the furnace power off for 30 seconds, and then restoring power. Some models have a reset button on the control board labeled “reset.” Only use the reset after addressing the underlying cause.

What Causes A Furnace To Smell When First Turned On?

Dust burning off the heat exchanger during the first heat cycle is common after long idle periods. Persistent or strong fuel odors require immediate inspection and possible gas leak response.

How Often Should The Flame Sensor Be Cleaned?

Cleaning the flame sensor annually during maintenance can prevent flame failure lockouts. Homes with dirty environments may require more frequent cleaning.

How To Know When To Replace The Furnace

Consider replacement when repair costs exceed 50% of a new system, if the unit is over 15–20 years old, or if inefficiency drives high energy bills. Newer furnaces offer significant efficiency gains and improved reliability.

Upgrading can also address recurring issues like frequent short cycling or a cracked heat exchanger that compromises safety.

Resources And Where To Get Professional Help

Contact local NATE-certified technicians for qualified service. Manufacturer customer support can assist with parts lookup and warranty questions.

Keep records of repairs and maintenance to streamline future service and warranty claims. Use trusted HVAC directories and review platforms to find reputable professionals.

Note: This article provides general guidance. For gas-related repairs and complex diagnostics, always consult a licensed HVAC technician to ensure safety and compliance with local codes.