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⚠️ Troubleshooting Guide: What Mike Did When His 3 Ton Horizontal AC Stopped Cooling

🧰 Introduction — My AC Crisis in July

It was July 2025, 96°F outside, and my house was heating up fast. I walked past a vent, and instead of the cool air I expected, it was just warm, weak airflow.

This was my Goodman 3 Ton Horizontal AC (R-32, Model GPCH33631) — brand new just a year earlier. I panicked. Did I just throw away $6,000 on a system that already failed?

Instead of rushing to call a contractor, I grabbed my tools and started a step-by-step troubleshooting routine. What follows is not just what I did, but also what I’ve learned about horizontal units in tight attic spaces, the unique challenges of R-32 refrigerant systems, and how to know when it’s time to call a professional.

🔌 1. First Checks — The “Quick Wins”

Before tearing open panels or suspecting refrigerant leaks, start simple.

✅ 1.1 Thermostat Settings

Ensure mode = COOL (not “FAN ONLY” or “HEAT”).
Verify setpoint is below indoor temp.
Replace batteries if the thermostat is wireless.

👉 In my case, the thermostat was set correctly.

Resource: Energy Star – Smart Thermostats

✅ 1.2 Breaker & Disconnect Box

Breakers trip often with surges.
Outdoor disconnect boxes may blow a fuse.
Reset carefully, but if it trips again → sign of an electrical issue.

✅ 1.3 Airflow at Vents

If no air: blower motor or duct blockage.
If weak airflow: clogged filter, duct leaks, or coil freeze.

👉 My airflow was present but warm. That told me the fan was fine, but cooling wasn’t happening.

🧹 2. Filter & Airflow Issues — The Most Common Culprit

Horizontal units installed in attics tend to face heavier dust loads and ductwork stress, making airflow and filter problems more likely than in vertical systems.

🛑 2.1 Dirty Filter

During my inspection, I found the air filter was past due — coated so heavily in dust that it blocked light through its pleats. A clogged filter chokes airflow, causes the evaporator coil to overcool, and in many cases leads to coil freeze-up.

Fix: I replaced it with a fresh MERV 8 pleated filter (a good balance of filtration vs. airflow for residential systems).

🛠️ 2.2 Leaky or Disconnected Ducts in the Attic

Next, I crawled into the attic and located a return duct collar that had slipped loose. This allowed hot attic air to be sucked directly into the system, diluting its cooling capacity and stressing the airflow balance.

Fix: I reattached and sealed the joint using foil-backed mastic and foil HVAC tape (not ordinary cloth duct tape, which degrades over time).

According to ENERGY STAR, poorly sealed ductwork can cause significant energy losses — in many homes, 20 to 30 per cent of conditioned air is lost due to leaks, holes, or improperly connected duct joints. Sealing leaks with mastic or metal-backed tape is a recommended homeowner measure. ENERGY STAR

👉 After I replaced the filter and resealed the duct joint, airflow improved noticeably — though the air was still warmer than expected, indicating deeper issues needed investigation.

❄️ 3. Frozen Coil — My “Ah-Ha” Moment

3.1 Signs of a Frozen Coil

Ice buildup on the suction line.
Condensation dripping in the attic.
Warm air from vents.

3.2 Why It Happens

Clogged filter (already fixed).
Low refrigerant charge.
Weak blower motor.
Restricted airflow in ducts.

3.3 My Solution

Turned the system OFF.
Set the fan to ON for 6 hours → melted ice.
Laid towels under the drain pan for water overflow.

Resource: Carrier – Frozen Coil Causes

👉 Melting the coil helped, but it refroze within 24 hours → pointed to a bigger problem.

💧 4. Condensate Drain Clog — Hidden Danger

A frozen coil often overwhelms the drain line, leading to clogs.

4.1 How I Checked

Poured water into the secondary drain pan.
No flow outside → confirmed blockage.

4.2 My Fix

Hooked the wet/dry vacuum to the outside drain line.
Pulled out algae sludge.
Flushed line with vinegar + water solution.
Installed a float switch (shuts system off if water backs up).

Resource: Energy Star – AC Maintenance

👉 Drain cleared, coil thawed, but the system still wasn’t cooling properly.

⚡ 5. Electrical Failures — Small Parts, Big Problems

Electrical failures are common in Goodman systems after 1–2 years, especially in hot attics, where components wear faster.

🔋 5.1 Capacitor

Symptom: Fan runs, compressor hums, but won’t start.
Tested with a multimeter → mine was weak.
Replaced with $35 OEM Goodman capacitor.

Resource: This Old House – Capacitor Costs

🔌 5.2 Contactor

Symptom: Clicking, burnt smell, or the system won’t power on.
Inspected → mine was pitted but still functional.
Pro replaced it later for $180.

👉 After capacitor swap, compressor kicked on again — but cooling was still weak.

🌀 6. Refrigerant Problems (R-32 Specific)

This is where DIY stops. Refrigerant = licensed tech only.

6.1 My Symptoms

The suction line is barely cool.
Coil icing repeatedly.
Weak cooling even after electrical fixes.

6.2 Pro Diagnosis

HVAC tech tested pressures → low R-32 charge.
Found a loose flare nut (factory issue).
Tightened connection, recharged with R-32.

Resource: EPA – Refrigerant Handling Rules

👉 Cost: $250 service. Without recharge, the compressor risked burnout ($2,000+ repair).

🔊 7. Troubleshooting by Noise

Noise tells stories. Here’s what I learned:

Buzzing → Bad capacitor or contactor.
Hissing → Refrigerant leak.
Rattling → Loose fan blade or mounting screws.
Grinding → Blower motor bearings failing.

Resource: Lennox – AC Noise Causes

👉 In my case, a faint hiss near the coil hinted at the refrigerant issue.

🛠️ 8. DIY vs. Professional Boundaries

Problem	DIY Safe?	Call Pro?
Thermostat reset	✅	–
Filter replacement	✅	–
Drain flush	✅	–
Duct sealing (small leaks)	✅	–
Capacitor (experienced DIY only)	⚠️	✅ safer
Contactor	⚠️	✅
Refrigerant leaks/recharge	❌ illegal	✅ required
Compressor replacement	❌	✅ required