Low Airflow After Install? The Great Guide to Setting the DIP Switches on the Goodman GLXS4BA3610 + AMST36CU1300

What’s Up, Team? It’s Mark Again 👷

So, you’ve got the new Goodman 3 Ton 14.5 SEER2 R-32 system in place. Lines vacuumed. Breakers flipped. Everything looks solid… until you realize your airflow feels like it’s coming from a squirrel-powered desk fan. 😬

That, my friend, is usually a DIP switch issue. It’s one of the most common mistakes I see—especially when folks assume factory settings are “close enough.”

Today, I’m breaking down how to set the DIP switches on the AMST36CU1300 air handler, why they matter, and how to match your system’s airflow to your ductwork like a boss.

Let’s get into it. 🔧💨

 

First Off: What Are DIP Switches and Why Do They Matter?

DIP switches (Dual Inline Package) are those tiny rows of toggles on your air handler’s control board. They control how your air handler behaves. Think of them like programming buttons for airflow, motor speed, and delays.

On the AMST36CU1300, these switches control:

• Blower speed (aka airflow/CFM)

• Tonnage match

• Dehumidification profiles

• Start-up and off delay times

If you leave them on the factory setting, chances are your system is:

• Moving the wrong amount of air

• Not removing enough humidity

• Causing noisy ducts or high static pressure

• Freezing the coil due to low airflow

Proper airflow is everything. According to Energy Vanguard, even a 15-20% reduction in airflow can throw off refrigerant pressures and tank your efficiency.

 

Before You Touch a Switch: Check These First ☑️

1. Verify the System Size
   The GLXS4BA3610 is a 3-ton condenser, so you need to set the air handler to match that 3-ton capacity (36,000 BTU/hr).

2. Inspect the Ductwork
   Your ductwork needs to be able to handle ~1,200 CFM for a 3-ton unit (that’s 400 CFM per ton). Undersized returns or long duct runs will create static pressure nightmares.

3. Measure Static Pressure
   Before adjusting anything, grab a manometer and take readings at the return and supply plenums. HVAC School has a killer walkthrough on how to do this if you’re rusty.

4. Check for Dirty Filters or Obstructions
   Obvious? Sure. Overlooked? Always.

 

Finding the DIP Switches on the AMST36CU1300

You’ll find them right on the blower control board inside the air handler compartment. Goodman labels these as S1, S2, S3 etc., depending on the board revision.

You’ll usually see:

• Switches 1–4: Control blower speed (airflow)

• Switches 5–6: Match tonnage

• Switches 7–8: Dehumidification mode or off-delay

Get out your flashlight, maybe even snap a picture before you start toggling so you can always roll back if needed.

 

Setting the Blower Speed (aka Airflow) – The Heart of the Matter 🫀

For a 3-ton system, you want to aim for:

• 1,200 CFM at high

• ~900–1,050 CFM at low/moderate (dehumid mode)

Use the Goodman airflow table (usually included on the air handler’s panel or available) to match your DIP settings to CFM based on static pressure.

Here’s a sample chart for context (values will vary by model revision):

Match your airflow to your ductwork’s ability. If you’ve got long runs or flex duct, go one step down to avoid pressurizing your system like a soda can.

Check out this Carrier Residential post that explains why too much airflow can actually be worse than too little, especially in newer homes with tight envelopes.

 

Matching Tonnage – Don’t Skip This One

If your air handler is a universal model (like many AMST units), it may ship ready to handle anything from 2 to 3.5 tons.

There’s a DIP switch setting to tell it, “Hey, I’m working with a 3-ton condenser here.” If you leave it wrong, you’ll get low airflow or worse—over-speeding on startup, which can trip the safety board.

You’ll usually see:

• Switch 5 ON = 3-ton

• Switch 5 OFF = 2.5-ton

Again, always consult the exact model wiring diagram. And if you don’t have it? You can usually find a PDF at Goodman’s Product Literature Library.

 

Optional Modes: Delay Settings + Dehumidification

Want that extra touch of comfort? Don’t sleep on these:

Off Delay

Keeps the blower running for a few seconds after the compressor shuts off, squeezing out every last bit of cold air.

Dehumidification Mode

In humid climates, you can set the blower to run slower during cooling, allowing the coil to pull more moisture from the air. Lower airflow = longer contact time = drier air.

 

Still Not Getting the Airflow You Need?

Sometimes it’s not just the DIP switches. If airflow is still weak after your changes, look into:

• Blower wheel direction (yes, it can be installed backward)

• Loose or unbalanced blower wheel

• ECM motor calibration error (reset the board)

• Undersized return grille or filter rack

Also, confirm that the blower motor is compatible with the ECM programming from the control board. Older or aftermarket motors may not behave as expected.

 

Safety First: Always Power Down Before Adjusting 🔌

This should go without saying, but every year someone gets zapped because they tried flipping switches on a live board. Don’t be that guy.

Power down at the disconnect, wait 3–5 minutes, and then open the panel. Only work on the board when the system is off and fully discharged.

 

Quick Case Study: What Happens If You Get It Wrong?

A buddy of mine installed the exact same GLXS4BA3610 + AMST36CU1300 system last summer. He left the DIP switches on the 2-ton setting because “it sounded quieter that way.”

Well… it also froze the coil, backed up the condensate drain, and dumped a gallon of water into the utility closet. 🤦

All it took was a 10-minute toggle flip and airflow jumped by 300+ CFM. Problem solved.

 

Final Thoughts from Mark 🤙

Look, this whole “DIP switch” thing might seem like a small detail, but it’s the secret sauce to getting your Goodman 3 Ton 14.5 SEER2 R-32 system humming along like a dream.

Don’t treat it like a checkbox. Understand it. Use it. Love it.

And if you haven’t snagged your system yet, or you’re trying to see what all the fuss is about, check it out over at The Furnace Outlet. I’ve worked with a lot of setups, and this one’s built for efficiency, power, and easy diagnostics—if you set it up right.

Is your AC going off? Visit: How to Fix Buzzing, Humming, or No Power on the Goodman GLXS4BA3610.

Catch ya next time—and remember: air that doesn’t move is air that doesn’t cool. 💨

Until next time,

- Mark, your go-to HVAC tech