Troubleshooting Guide: What to Do If Your Daikin System Isn’t Cooling Properly

When your Daikin Light Commercial 5 Ton Multi-Positional AC Split System with 13.4 SEER2 suddenly stops cooling like it used to, it’s easy to panic — especially on a hot day. But not every issue means an expensive repair. Sometimes, the fix is as simple as cleaning a filter, clearing debris, or checking thermostat settings.

In this troubleshooting guide, we’ll walk through:

Step-by-step airflow, filter, and refrigerant checks
The most common causes of reduced cooling capacity
When it’s time to call in a professional

Ready to get your Daikin back to peak performance? Let’s dive in.

1. Step-by-Step Walkthrough: Airflow, Filter, and Refrigerant Checks

Before you grab the phone to call your HVAC tech, perform these simple (and safe) checks. You might find and fix the issue yourself.

Step 1: Check the Thermostat

Confirm the mode is set to Cool and the fan to Auto.
Make sure the set temperature is at least 5°F lower than the current room temperature.
Replace thermostat batteries if it’s unresponsive or acting erratically.
If you have a smart thermostat, check for Wi-Fi disconnections or software errors.

👉 Pro Tip: Thermostats mounted near windows, kitchens, or return vents can read temperatures inaccurately and mislead your system, according to tbyrdhvac.com .

Step 2: Inspect Air Filters

A dirty air filter is the #1 cause of weak airflow and poor cooling. It restricts air movement, causes ice buildup on the evaporator coil, and forces the compressor to overwork.

How to check it:

Locate your system’s return grille or filter slot near the air handler.
Remove the filter and hold it up to a light.
- If you can’t see through it clearly, it’s clogged.
Replace with the correct size and airflow direction (arrow should face toward the blower).

Recommended frequency:

Every 1 month in commercial spaces
Every 2–3 months in light residential use

According to Energy.gov , regular filter replacement can lower energy consumption by up to 15%.

Step 3: Check Airflow from Vents

If some rooms are getting cool air while others feel warm:

Make sure supply vents and returns are open and unobstructed by furniture or curtains.
Look for weak airflow—that could indicate duct leaks, blocked dampers, or a failing blower motor.
If you have multiple zones, verify all zone dampers are open (you may hear them click when adjusting thermostats).

To test airflow: Hold a sheet of paper near a vent. If it barely moves, you may have a restriction somewhere in the system.

Step 4: Inspect the Outdoor Unit

Go outside and locate your Daikin condenser.

Check for:

Blocked airflow: Remove leaves, dirt, or debris around the unit (keep at least 2 feet of clearance).
Dirty coil fins: Gently rinse with a garden hose (from inside out). Never use high pressure—it bends fins.
Fan operation: Ensure the fan spins smoothly when cooling starts.
Weeds or nests: Remove anything obstructing airflow.

If you hear loud humming, clicking, or grinding, turn off the power — your fan motor or compressor may need professional attention.

Step 5: Check the Evaporator Coil (Indoor Unit)

If your system is running but air from the vents feels warm:

Open the access panel and inspect for ice buildup on the coil.
- If frozen, shut off the system immediately and let it thaw for several hours.
- Then check your air filter again—low airflow is often the cause.
If ice reappears, you could have low refrigerant or poor coil drainage.

Frozen coils are a warning sign, not a normal condition. Continuing to run the system can damage the compressor.

Step 6: Refrigerant Checks (Visual, Not Hands-On)

Only licensed technicians should handle refrigerants, but you can still observe clues:

Bubbling or hissing near copper lines? May indicate a leak.
Frost on the suction line (thicker insulated pipe)? Often linked to a low refrigerant charge.
Warm air at vents despite running the compressor? Could indicate undercharge or restriction.

If you suspect a refrigerant issue, call a pro — handling refrigerant without certification is illegal and unsafe.

ACHR News reports that small leaks often start at flare fittings, valve cores, or coil joints — all fixable if caught early.

2. Common Causes of Reduced Cooling Capacity

When your Daikin system doesn’t cool properly, several common culprits may be at play — and knowing how to identify them can save you both time and money.

2.1 Clogged or Dirty Air Filters

As mentioned, restricted filters are the top reason for poor cooling. They cause low airflow, coil freezing, and temperature imbalance.

Fix: Replace filters immediately and set a reminder for the next change.

2.2 Low Refrigerant Charge or Leak

Your Daikin uses a sealed refrigerant system. Leaks cause a gradual cooling decline and a higher power draw.

Fix: Have a certified HVAC technician locate and repair leaks, then recharge with the correct refrigerant amount per Daikin’s specifications.

2.3 Dirty Coils (Indoor or Outdoor)

Dust and grease insulate coils, blocking heat transfer. This means your system runs longer, but the air never gets as cool.

Fix: Clean coils every 6–12 months. Coil cleaners or low-pressure rinsing are safe options.

Carrier.com notes that dirty coils can cut cooling efficiency by up to 30%.

2.4 Faulty Blower or Motor Issues

If the indoor fan motor fails, you’ll feel weak or no airflow even if the condenser is running outside.
Listen for humming or squealing — signs of worn bearings or seized fan motors.

Fix: Shut off power and call a technician for motor testing and capacitor inspection.

2.5 Frozen Evaporator Coil

If you see frost on the coil or suction line:

Turn off the system.
Replace the filter and check for blocked returns.
Restart after thawing (4–6 hours).

Persistent freezing means low refrigerant or a malfunctioning blower.

2.6 Thermostat or Control Board Failure

If the system doesn’t respond to temperature changes, your thermostat or zone control panel could be malfunctioning.
Fix: Reset the thermostat or replace batteries. If the problem persists, contact a Daikin service professional.

2.7 Ductwork Problems

Leaks, crushed ducts, or unbalanced airflow can cause one area to cool while another bakes.

Fix: Inspect accessible ductwork for damage or disconnections. Have a pro perform an airflow test and duct sealing if necessary.

3. When It’s Time to Call a Professional

You’ve checked everything within reach, but your Daikin system still isn’t cooling properly — now what?

Here are the clear indicators it’s time to bring in a licensed technician:

3.1 The Coil Keeps Freezing or the Compressor Keeps Shutting Off

Recurring freeze-ups signal refrigerant issues or blower motor failure — problems only pros can diagnose with gauges and meters.

3.2 You Hear Grinding, Buzzing, or Popping Noises

These noises suggest worn bearings, failing capacitors, or even electrical arcing. Shut off the unit immediately and don’t restart it.

3.3 Refrigerant or Oil Spots Near Lines

Oil stains often mean a refrigerant leak. This needs prompt repair to prevent compressor damage.

3.4 The Breaker Trips Repeatedly

Frequent tripping indicates short circuits or overloaded motors. Never reset breakers repeatedly — it’s a fire hazard.

3.5 Airflow Seems Fine, but Air Is Still Warm

If airflow is normal but cooling is weak, the compressor or expansion valve may be malfunctioning — both require professional service tools to test.

3.6 System Age and Maintenance History

If your Daikin system is over 15 years old and showing frequent cooling issues, it may be time for a professional evaluation of repair vs. replacement. Sometimes upgrading to a newer SEER2 model provides better efficiency and lower lifetime cost.

4. Samantha’s Pro Tips for Preventing Future Cooling Problems

Schedule professional tune-ups twice a year. Spring for cooling, fall for heating.
Keep coils and filters spotless. Small effort, huge payoff in performance.
Clear 2 feet around the outdoor unit. Airflow is everything.
Check thermostat placement. Keep it away from sunlight and vents.
Inspect ductwork every 2–3 years. Especially for commercial or high-dust spaces.
Document every service. Helps diagnose recurring issues faster.
Use surge protectors and proper voltage regulation. Electrical issues can silently shorten compressor life.

5. Final Thoughts from Samantha

If your Daikin 5-ton system isn’t cooling properly, start simple — check airflow, filters, and coils before assuming the worst. Most issues stem from minor neglect rather than major component failures. But when the signs point to refrigerant, electrical, or compressor problems, it’s best to call in a certified technician.

A quick maintenance routine and early detection can prevent small issues from turning into system replacements — keeping your Daikin running cool, efficient, and dependable for many years.

In the next blog, you will uncover "A Guide to Picking the Right Daikin System".