Troubleshooting Guide: What to Do If Your Furnace or AC Stops Working

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When your home’s heating or cooling system suddenly stops, it can feel like panic mode. The house starts getting chilly (or uncomfortably hot), the thermostat blinks, and you wonder: “Is it something serious, or can I fix it myself?”

For Mike Sanders, a hands-on homeowner in upstate New York, the first time his Goodman 96% AFUE furnace stopped mid-cycle, he thought the worst — until he learned most HVAC issues come down to small, simple fixes.

💬 “I used to think ‘no heat’ meant disaster. But after a few experiences, I realized it’s often something small — like a tripped breaker or a dirty filter.”

This guide is written for homeowners like Mike — people who want to stay calm, troubleshoot smartly, and understand when it’s time to call a pro. Whether you have a Goodman furnace, 14 SEER2 air conditioner, or any dual system, this step-by-step checklist will walk you through exactly what to do when comfort suddenly stops.

⚠️ 1️⃣ Step One: Stay Calm and Stay Safe

Before you do anything, remember: safety first.

If you smell gas, see sparks, or notice burning odors, turn the system off immediately and call a licensed HVAC technician or your gas utility emergency line.

For all other cases, take a deep breath. Many system “failures” are actually just protective shutoffs or minor power issues. Goodman systems are designed with smart diagnostics to prevent damage and alert you before serious problems happen.

“Goodman built these systems to be smart. If something goes off, it’s usually the system protecting itself.”

🔌 2️⃣ Step Two: Check the Power Supply

It sounds obvious, but power interruptions are the number one reason for furnace and AC outages.

✅ For the Furnace:

Make sure the furnace switch (usually near the unit) is in the “On” position.
Check the breaker panel — the furnace should be on its own circuit. Reset if tripped.
Verify that the blower door is fully closed — Goodman furnaces have safety switches that stop operation when the panel is open.

✅ For the Air Conditioner:

Locate the outdoor disconnect box near the condenser — ensure the pull-out fuse block is seated correctly.
Inspect the breaker labeled “AC” in your panel. If tripped, reset it once.

If the breaker trips again immediately, don’t force it — that’s a sign of a deeper electrical issue needing professional inspection.

📘 Reference: Energy.gov – Central Heating Systems

“Once, my furnace went dark right before a snowstorm. Turned out, the power switch looked ‘on’ — but wasn’t fully flipped. Rookie mistake.”

🌡️ 3️⃣ Step Three: Check the Thermostat

Your thermostat is the command center of your HVAC system, and simple settings or dead batteries can halt everything.

🧭 Run through this checklist:

Is the display lit? If not, replace the batteries.
Make sure the thermostat is set to HEAT or COOL, not “Off.”
Set the temperature 3–5°F higher (for heat) or lower (for cooling) than the current room temperature.
Check for “Hold” or “Vacation” modes that might override your usual program.
For smart thermostats, verify Wi-Fi connection and app control are functioning.

📘 Reference: ENERGY STAR – Thermostat Troubleshooting Tips

“The first time my AC stopped responding, I thought it was a compressor issue. Nope — thermostat batteries.”

💨 4️⃣ Step Four: Check Airflow — The Hidden Culprit

If your system is running but not heating or cooling effectively, airflow could be the issue.

🧹 Start with the air filter:

Pull out your filter and hold it up to the light. If you can’t see through it, replace it.
Goodman furnaces are sensitive to airflow restriction — clogged filters can cause overheating lockouts or frozen coils.
Check vents and returns throughout your home. Ensure none are blocked by furniture or drapes.

“My AC once iced over completely. The technician asked one question — ‘When was the last time you changed your filter?’ Lesson learned.”

📘 Reference: Energy.gov – Air Filter Maintenance Guide

🔥 5️⃣ Step Five: Furnace-Specific Troubleshooting

Your Goodman furnace has built-in protection features that can tell you exactly what’s wrong — if you know how to read the signs.

🧠 Step-by-step:

Check for LED diagnostic lights on the furnace’s control board.
- Look through the small viewing window; count the flashes.
- Match them to your model’s code list (usually on the inside panel).
Inspect the vent pipes — blockages (from snow, leaves, or debris) can trip the pressure switch and shut the system down.
Confirm gas supply — the valve handle should be parallel to the gas line.
Reset the furnace:
- Turn off power for 30 seconds.
- Turn back on and wait for the ignition sequence.
Clean flame sensor (for those comfortable doing so). A dirty sensor prevents ignition.

📘 Reference: Goodman Furnace Owner’s Manual

Flash Pattern	Meaning	Solution
1 Flash	Ignition failure	Check gas and sensor
3 Flashes	Pressure switch open	Inspect vent piping
6 Flashes	Flame sensor error	Clean or replace sensor
Continuous	Normal operation	System OK

“After a snowstorm, my Goodman furnace kept shutting off. I found the intake pipe half buried in snow. Cleared it, and the heat came right back.”

❄️ 6️⃣ Step Six: Air Conditioner Troubleshooting

Summer failures can be just as stressful — but again, many issues are minor.

☀️ Quick checks for your Goodman 14 SEER2 AC:

Make sure the thermostat is set to COOL, and the fan to AUTO.
Inspect the outdoor unit for leaves, twigs, or dirt buildup.
Check if the fan blades are spinning when the compressor hums.
If you see frost on the copper lines or coil, turn off the system and allow it to thaw for 2–3 hours.
Inspect the drain pan and condensate line — clogs trigger the safety float switch and shut the unit down.

📘 Reference: Goodman Air Conditioner Maintenance Guide

“Last summer, my AC stopped cooling. The culprit? A clogged condensate drain. Five minutes of cleaning saved a $200 service call.”

💡 7️⃣ Step Seven: Reset and Observe

If your system has power but isn’t running properly, try a full reset:

Turn off power at the breaker.
Wait 60 seconds.
Turn it back on and reset the thermostat to Auto mode.

Some Goodman systems have built-in time-delay relays to prevent short cycling. After restoring power, give it 5–10 minutes to restart.

“Patience pays off — modern systems take a few minutes to re-sync after power loss.”

🔋 8️⃣ Step Eight: Check the Condensate Pump and Drain Line

If your furnace or AC shuts down unexpectedly and you notice water nearby, this might be your problem.
A blocked drain or failed pump can trip a safety switch.

🧰 Fix it safely:

Turn off system power.
Locate the PVC drain pipe — remove and flush with a 50/50 vinegar and water mix.
If you hear the condensate pump humming but not draining, clean or replace it.

📘 Reference: Energy.gov – HVAC Condensate Drain Maintenance

“When my system stopped on a humid day, I thought it froze. Nope — the drain pump float switch shut it down. Ten minutes later, it was fixed.”

🧠 9️⃣ Step Nine: Listen, Look, and Smell

Sometimes the best diagnostic tools are your own senses.

🕵️♂️ Pay attention to:

Clicking but no ignition: Likely a flame sensor or gas flow issue.
Humming only: Could be a stuck blower motor or capacitor.
Musty odors: Possibly mold in the evaporator coil or ducts.
Burning smell: Dust buildup on the heat exchanger after long inactivity (normal at first startup).

“If your system smells like gas or burnt wiring, turn it off. That’s when you call a pro.”

🧯 🔟 Step Ten: When to Stop and Call a Professional

DIY has its limits. You should always call an HVAC technician if:

You smell gas or fuel.
Breakers keep tripping.
Ignition fails repeatedly.
You find ice buildup on refrigerant lines.
The blower runs constantly or never turns on.
The system locks out after multiple resets.

📘 Reference: Goodman Dealer Locator

“Knowing when not to DIY is part of being a good DIYer.”

🧰 11️⃣ Mike’s “HVAC First Aid Kit” for Homeowners

Keeping a small kit nearby saves time during troubleshooting.

🧺 Mike’s Toolkit Includes:

Flashlight
Screwdriver set
Filter replacements (16x25x1 MERV 8)
Thermostat batteries
Small cup of white vinegar (for drains)
Shop towel or rag
Multimeter (optional, for checking voltage)

“I keep everything labeled in a small plastic tote. When something happens, I don’t scramble — I grab and go.”

🧹 12️⃣ Preventive Maintenance: Avoiding Future Breakdowns

The best troubleshooting is the kind you never have to do.
Here’s Mike’s routine for keeping his Goodman system in top shape:

Task	Frequency	Benefit
Replace air filter	Every 2–3 months	Prevents lockouts and overheating
Clean outdoor condenser	Twice per year	Improves cooling efficiency
Check thermostat calibration	Annually	Ensures accurate temperature control
Inspect drain line	Each spring	Prevents safety shutdowns
Schedule pro tune-up	Annually	Extends lifespan, maintains warranty

📘 Reference: Energy Star – HVAC Maintenance Checklist

“Maintenance doesn’t just prevent problems — it keeps your system efficient and your bills lower.”

🧾 13️⃣ Maintenance Logs: The Secret Weapon

Mike keeps a simple notebook for all service and filter changes.
That way, he can track when something started acting up and what’s been done.

Date	Action	Notes
Jan 2025	Filter replaced	Clean airflow, quieter fan
Apr 2025	Drain line flushed	No water backup
Oct 2025	Annual tune-up	Technician adjusted blower speed

“When my technician asked about past service, I handed him my log — he said most homeowners never think to do that.”

⚙️ 14️⃣ Understanding Goodman’s Built-In Safeguards

Goodman systems come with intelligent safety features that shut down the unit automatically when unsafe conditions occur:

Pressure switches monitor venting and shut off the gas valve if blocked.
Limit switches prevent overheating by stopping the burners when airflow is restricted.
Lockout control resets after several failed ignition attempts.
Compressor time-delay relays protect against rapid cycling.

Understanding these safeguards prevents panic — if your system isn’t running, it may just be keeping itself safe.

“Sometimes it’s not broken — it’s doing its job to protect itself.”

🌬️ 15️⃣ Smart Thermostats Make Troubleshooting Easier

Smart thermostats like Ecobee Premium or Google Nest integrate with Goodman systems and provide:

Real-time alerts for system issues (low airflow, ignition failure, etc.).
Historical runtime data.
Remote shutdown/restart capability.
Energy use tracking.

📘 Reference: ENERGY STAR – Smart Thermostat Features

“My thermostat told me about a low airflow issue before I even felt a difference. That’s next-level troubleshooting.”

🧩 16️⃣ How to Reset Goodman Error Codes

If your system displays an error after you’ve resolved the issue:

Turn off power to the furnace or condenser.
Wait 30–60 seconds.
Turn power back on.
The LED should clear if the problem no longer exists.

If it persists, take a photo of the flashing code and contact a Goodman dealer.

💡 17️⃣ Quick Troubleshooting Flowchart

Symptom	Possible Cause	DIY Fix	Call Pro?
No power	Tripped breaker	Reset once	If reoccurs
No heat	Dirty filter	Replace	If still cold
Furnace short cycling	Clogged vent or sensor	Inspect & clean	If continues
No cooling	Frozen coil or clogged drain	Thaw & clean drain	If re-freezes
System loud	Loose panel or dirty fan	Tighten & clean	If vibration persists
Odor	Dust or gas leak	Run or shut down accordingly	Always if gas odor

This table helps homeowners decide when it’s safe to troubleshoot — and when to step back.

🧭 18️⃣ When to Schedule a Professional Tune-Up

Even if your system runs fine, annual maintenance keeps it that way.
Professionals can:

Measure gas pressure and airflow.
Clean ignition assembly and burners.
Verify refrigerant charge.
Test safety sensors.
Spot issues before they cause shutdowns.

“I schedule my tune-up every October — it’s cheaper than an emergency repair and gives me peace of mind before winter.”

🧠 19️⃣ Mike’s Golden Rule for Home Comfort

“If you can safely reset, clean, or clear something — do it. If it involves gas, wires, or refrigerant — call a pro.”

That simple mindset keeps Mike’s Goodman system running year after year with minimal issues.

🌡️ 20️⃣ The Bottom Line: Confidence, Not Panic

Modern HVAC systems are built with layers of protection and self-diagnostics.
For homeowners, understanding how to read, reset, and maintain your Goodman system can save hundreds of dollars in unnecessary service calls — and prevent downtime when you need comfort most.