Goodman Gas Furnace Troubleshooting Guide

The following guide provides concise, actionable Goodman Gas Furnace Troubleshooting steps for homeowners and technicians in the U.S. It covers common fault indicators, diagnostic checks, safety precautions, and next steps to restore reliable heating.

Symptom	Likely Causes	Quick Fix
Furnace Won’t Start	Thermostat, power, gas supply, ignition failure	Check power and thermostat, reset breaker, verify gas valve
Intermittent Heating	Dirty flame sensor, clogged filter, pressure switch	Clean sensor, replace filter, inspect venting
Short Cycling	Overheating, limit switch, undersized airflow	Replace filter, check blower, test limit switch
Blower Runs Constantly	Fan setting, control board, thermostat fan	Set thermostat fan to auto, inspect control board

Safety First: Before Any Troubleshooting

Always prioritize safety when performing Goodman Gas Furnace Troubleshooting. Turn off electrical power at the furnace switch or breaker and shut off the gas supply if smelling gas. Use a non-contact voltage tester when needed and ventilate areas with suspected gas leaks.

If A Gas Leak Is Suspected: Evacuate occupants, avoid sparks or flames, call the gas company or 911 from a safe distance. Do not attempt repairs until the leak has been confirmed safe.

Understanding Error Codes And LED Blink Patterns

Goodman furnaces display diagnostic information via a status LED on the control board. LED blink sequences identify specific faults for targeted troubleshooting.

Common LED Blink Codes

• 1 Blink: Limit switch lockout or pressure switch failure.
• 2 Blinks: Pressure switch stuck open or venting issue.
• 3 Blinks: Flame sensing or ignition failure.
• 4 Blinks: Rollout switch or blocked heat exchanger detection.
• 5+ Blinks: Control board faults, gas valve, or communication errors.

Consult the model-specific manual for precise code definitions; blink counts and durations vary by control board series.

Initial System Checks

Begin Goodman Gas Furnace Troubleshooting with basic checks that resolve many issues quickly: ensure the thermostat is set to heat and a temperature above room temperature; confirm circuit breaker and furnace switch are on; verify gas supply and pilot (if present).

Also inspect the air filter and return vents. A clogged filter reduces airflow, causing short cycling and overheating that can trigger safety limits.

Thermostat And Controls

Thermostat faults mimic furnace problems. Replace batteries if applicable and confirm wiring connections are tight. Use a multimeter to test for a 24VAC signal at the furnace R and W terminals when heat is demanded.

If the thermostat calls for heat but the furnace doesn’t respond, the issue may be at the control board, door switch, or a blown fuse on the furnace control. Check the low-voltage fuse and door interlock switch.

Ignition And Flame Sensing Issues

Ignition failure and flame sensing problems are among the most common causes of no-heat calls. Goodman furnaces typically use hot surface igniters (HSI) or direct spark ignition (DSI).

Hot Surface Igniter (HSI) Troubleshooting

• Inspect for cracks or white powder on the igniter; replace if damaged.
• Measure resistance with an ohmmeter; a cold HSI often reads 40–90 ohms depending on model.
• Check for proper 120/240VAC and control board signals controlling the HSI.

Flame Sensor Cleaning

A dirty flame sensor prevents consistent flame detection and will cause multiple ignition attempts then lockout. Remove the sensor and clean gently with fine-grit sandpaper or emery cloth, then re-seat securely.

Gas Valve And Supply Issues

Verify the gas shutoff valve at the furnace is open and that the home gas supply is active. If gas flow is present but the valve does not open, the control board or gas valve coil may be faulty.

Check for a clicking or humming sound from the gas valve during ignition. No sound with correct control signals suggests a failed valve or wiring issue; measure voltage to the valve when the thermostat calls for heat.

Pressure Switch And Venting Problems

The pressure switch confirms inducer fan operation and safe venting. A stuck-open or stuck-closed pressure switch can prevent ignition.

• Inspect venting for blockages, bird nests, ice, or loose connections.
• Test the pressure switch tubing for cracks or blockages; replace tubing if soft or collapsed.
• Use a manometer to verify inducer draft and pressure switch operation when the inducer starts.

Limit Switch, Rollout Switch, And Overheating

Limit switches protect the furnace from overheating. Recurrent trips indicate airflow restriction or a failing blower.

• Check air filter, registers, and return ducts for blockages.
• Inspect the blower motor for worn bearings or a failing capacitor.
• Examine heat exchanger and combustion chamber for signs of restriction or debris.

If a rollout switch trips, inspect the heat exchanger and burner alignment; cracks or blockage require professional evaluation due to CO risk.

Blower Motor And Airflow Diagnostics

Poor airflow causes inadequate heating and system stress. Measure static pressure if available and compare to manufacturer specifications.

• Verify blower wheel is clean and spins freely.
• Test blower motor capacitor and motor current draw; replace if out of spec.
• Confirm blower control settings and limit relays on the control board are correct.

Combustion Air And Heat Exchanger Concerns

Inspect the heat exchanger for corrosion, cracks, or signs of combustion leaks. Any suspected heat exchanger failure requires immediate professional service because of carbon monoxide hazards.

Ensure combustion air intake is clear and properly sized. Negative house pressure can affect combustion and venting—consider combustion air make-up solutions in tightly sealed homes.

Maintenance Tasks That Prevent Issues

• Change Air Filters: Replace every 1–3 months depending on use and filter rating.
• Annual Tune-Up: Schedule a professional inspection for burner cleaning, heat exchanger check, and efficiency tuning.
• Clean Flame Sensor & Burners: Do this yearly to avoid ignition and flame detection problems.
• Inspect Venting: Check for obstructions, corrosion, and secure pipe joints.

Tools And Equipment For Troubleshooting

Essential tools for Goodman Gas Furnace Troubleshooting include a multimeter, manometer, non-contact voltage tester, small mirror, flashlight, nutdrivers, replacement filters, and a fine-grit cloth for cleaning the flame sensor.

Advanced diagnostics may require combustion analyzers and amp probes used by HVAC technicians for safe, accurate testing.

When To Call A Professional

Contact a licensed HVAC technician when encountering suspected gas leaks, heat exchanger cracks, recurring limit switch trips, or any condition involving combustion safety and carbon monoxide risk.

Also call a pro for complex electrical controls, PCB replacement, or if diagnostic steps do not restore normal operation after basic troubleshooting.

Common DIY Fixes Versus Professional Repairs

DIY Fixes	Professional Repairs
Replace air filter, clean flame sensor, check thermostat settings, reset breaker	Heat exchanger repair, gas valve replacement, combustion analysis, control board replacement
Clear simple vent obstructions, replace igniter (if comfortable)	High-voltage or gas line work, pressure switch calibration, brazing or welding

Documentation And Parts Identification

Record the furnace model and serial number from the rating plate for parts lookup and accurate troubleshooting. Goodman model numbers indicate series and capacities useful for ordering compatible parts.

Keep the furnace manual and wiring diagram on hand. The control board schematic often lists LED codes and terminal functions critical for diagnostics.

Preventive Tips To Extend Furnace Life

• Maintain consistent filter changes and yearly professional service.
• Keep returns and registers unobstructed for proper airflow.
• Install a carbon monoxide detector near sleeping areas and on each level of the home.
• Consider a programmable thermostat to reduce cycling and wear.

Troubleshooting Checklist

1. Verify power, thermostat, and gas supply.
2. Check and replace air filter if dirty.
3. Observe LED blink codes and consult manual.
4. Inspect and clean flame sensor and burners.
5. Test igniter and measure voltages at the gas valve.
6. Inspect venting and pressure switch tubing.
7. Measure blower motor function and airflow.
8. If unresolved, contact a licensed technician.

Following this structured approach to Goodman Gas Furnace Troubleshooting helps isolate common faults quickly while protecting household safety. When in doubt about combustion safety or gas components, always engage a qualified HVAC professional.