Alright, Let’s Fix That Thing 🔧
Hey there, techs and tinkerers 👋 Jake here, and today we’re breaking down how to troubleshoot your 3.5 Ton R-32 AC and gas furnace system like a pro. If your outdoor unit’s quiet, the indoor blower’s acting funky, or the furnace keeps cycling off too fast, this guide’s got your back.
You don’t need to memorize the whole HVAC manual—you just need the right questions in the right order. So pour a coffee, grab a multimeter, and let’s get into it.
⚡ Start With Safety First
Before you even touch a wire or pull a panel, do this:
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Kill power at the disconnect and breaker
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Use a non-contact voltage tester to double-check
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Confirm gas valve is off (if working on the furnace)
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Make sure condensate pans are dry and stable
Never troubleshoot hot unless you’re experienced and know your paths. Electricity doesn’t care how long you’ve been doing this.
🔍 Step 1: Is the System Getting Power?
This might sound too obvious, but you’d be surprised how often it’s just a popped breaker or a blown fuse.
Checklist:
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✅ Check breaker panel for the furnace and condenser
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✅ Check furnace board LED – is it blinking?
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✅ Verify disconnect box is secure and line voltage present
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✅ Check low-voltage fuse on the furnace board (usually 3–5 amp blade fuse)
Pro Tip: A bad transformer can give you a blank thermostat, even if line voltage is fine. Pull out the multimeter and test the R and C terminals—you should see 24V AC.
🌬️ Step 2: AC Blowing Warm Air?
If the air is moving but not cooling, the problem likely lives outside (or in your refrigerant line). Start here:
A. Outdoor Unit Not Running?
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Is the contactor pulled in?
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If yes, test capacitor with a multimeter.
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If no, check the low-voltage signal from Y at the contactor.
A dead capacitor is one of the most common failures. If it’s bulging like a can of soda in July, replace it.
Want a deep dive? HVAC.com breaks down A/C capacitor testing.
B. Low or No Refrigerant?
Got gauges? Hook ‘em up and compare pressures with the R-32 spec sheet (found in Goodman’s product technical guides).
Signs of a leak:
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Low suction pressure
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High superheat
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Ice on evaporator coil
Leak test with bubbles, UV dye, or a digital detector. No refrigerant? You’ve found the culprit. Always follow EPA Section 608 rules before adding or recovering refrigerant—read more here.
🔥 Step 3: Furnace Acting Up?
R-32 systems with 96% AFUE gas furnaces like the Goodman GR9T961005CN are smart—but that means more sensors to trip.
A. Furnace Doesn’t Ignite?
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Is the inducer motor running?
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Check the pressure switch—disconnect the hose and blow through gently
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Look for a flashing fault code on the control board (3 blinks = pressure switch open)
Still nothing? Clean the flame sensor with steel wool. A dirty sensor causes ignition failure faster than you’d think.
Here’s a handy breakdown of Goodman furnace fault codes from McCorry Comfort.
B. Short Cycling?
If your furnace fires up then shuts down fast, check:
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Thermostat wire connections (especially W/W2)
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Dirty air filter or restricted return duct
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Limit switch (test continuity when cool)
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Oversized system causing high-limit trips
HVAC School’s guide explains the mechanics of short cycling and what to check.
🌀 Step 4: Weak or No Airflow?
No air? Little air? Let’s walk through it.
A. Blower Motor Not Running
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Check G terminal at control board—should show 24V when fan is ON
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Test capacitor (PSC motors)
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For ECM motors, check incoming 24V and DC voltage at control module
If the motor hums but doesn’t spin, the bearings are probably shot. Replace the motor or module.
B. Clogged Filter or Coil
Yup—sometimes it’s just a filter that hasn’t been changed since the Obama administration. Replace it. Still low flow? Inspect the evaporator coil for dirt or icing.
Coils dirty? I like using Nu-Calgon Evap-Green—safe for indoor use and doesn’t stink up the house.
💦 Step 5: Condensate Woes
Water around the furnace? That’s no good.
Common Issues:
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Clogged primary drain
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Missing or tripped float switch
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No trap on the drain line (yes, that matters!)
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Condensate pump failure
Test the float switch and run vinegar through the drain line. Pro tip: trap the drain after the coil outlet and make sure there’s a cleanout tee.
When to Call in Backup 🆘
Some issues aren’t worth risking your system—or safety—over. If you hit any of these, call a licensed HVAC tech:
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System is still under manufacturer warranty
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R-32 refrigerant leak with no license to handle it
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Gas smell or suspected heat exchanger crack
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Burned wiring or shorted control board
You can find a certified pro through NATE: https://www.natex.org/
Don’t Forget the Big Picture
Your HVAC system is only as strong as its weakest part. Even a perfectly installed 3.5 Ton R-32 system from The Furnace Outlet can act up if:
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Ducts are leaking
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Thermostat wires are loose
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Filters aren’t changed regularly
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Drain lines aren’t maintained
A little seasonal TLC keeps you from needing major repairs later.
Wrapping It Up
Troubleshooting a 3.5 Ton R-32 AC and gas furnace system isn’t about guessing—it’s about knowing what questions to ask and where to look. Once you’ve got that down, fixing a no-cool or short cycle is just another Tuesday.
Grab your multimeter, follow the signs, and don’t overthink it. And hey—if you’re ready to upgrade your system or help a client replace theirs, check out The Furnace Outlet’s full collection. They’ve got the bundles, coils, and furnaces ready to ship and priced right.
Is your 3.5-ton R-32 system leaking? Visit my guide: How to Diagnose and Fix It Fast.
Until next time—stay grounded, stay cool ❄️🔥
- Jake, your comfort loving tech
