Troubleshooting Guide: What to Do If Your MRCOOL Advantage Isn’t Cooling or Heating

👋 Introduction: When Comfort Takes a Hit

Hi folks, Mike here again.

Few things are more frustrating than switching on your MRCOOL Advantage 9k mini split only to realize it’s not cooling in the summer—or worse, not heating in the winter.

The good news? In most cases, the problem isn’t catastrophic. Many issues are simple fixes you can handle yourself with a little patience and know-how.

In this guide, I’ll walk you step by step through common reasons your MRCOOL Advantage might stop cooling or heating—and what you can do about it before calling in a professional.

---

🔎 Step 1: Check the Basics First

Sometimes the fix is easier than you think. Start with these quick checks:

• ✅ Remote Settings – Make sure it’s on the correct mode (cool/heat/fan/auto).

• ✅ Temperature Setting – Confirm the set temperature is below (for cooling) or above (for heating) the current room temperature.

• ✅ Power Supply – Check the breaker and ensure the unit hasn’t lost power.

• ✅ Batteries – Replace batteries in your remote if buttons aren’t responding.

Mike’s Tip: I once thought my mini split was broken—turned out the remote batteries were dead. Simple fixes first!

---

🧼 Step 2: Inspect & Clean the Filters

Clogged air filters are the #1 cause of poor performance.

• Remove and check the indoor unit filters.

• If dusty, vacuum or wash them with warm water and mild soap.

• Let them dry fully before reinstalling.

Dirty filters = blocked airflow, which makes the unit struggle to cool or heat.

👉 This alone fixes the issue in many cases.

Reference: Energy.gov – Maintaining Air Conditioners

---

❄️ Step 3: Check the Indoor & Outdoor Coils

If the indoor coil is dirty or iced over, or if the outdoor condenser coil is clogged with debris, the system can’t transfer heat effectively.

What to Do:

• Indoor Coil: Turn off unit, remove filters, inspect coil. If iced, let it thaw fully. Clean gently with coil cleaner.

• Outdoor Coil: Clear leaves, dirt, or grass clippings. Rinse gently with a hose.

Mike’s Tip: Never use a pressure washer on coils—it bends fins and ruins performance.

---

💧 Step 4: Check the Drain Line

If the condensate drain line is clogged, the system may shut down or stop cooling to prevent water damage.

What to Do:

• Locate the drain line at the indoor unit.

• Use a wet/dry vacuum or flush with vinegar to clear blockages.

• Look for leaks or water pooling around the unit.

---

⚡ Step 5: Review Error Codes

Your MRCOOL Advantage has built-in diagnostics.

• Look at the LED display or remote for error codes.

• Refer to your MRCOOL manual 

Common codes may indicate:

• Low refrigerant

• Sensor issues

• Fan problems

• Communication errors between indoor/outdoor units

---

🌡️ Step 6: Consider the Room Environment

Even a perfectly working MRCOOL can struggle under certain conditions:

• Oversized or undersized unit – A 9k BTU is best for ~300–400 sq ft. Too big or too small = comfort issues.

• Extreme heat/cold – Heat pumps lose efficiency below freezing.

• Open windows/doors – Escaping air will make it feel like the system isn’t working.

👉 Make sure your space matches the system’s capacity.

Reference: ENERGY STAR – Right-Sizing Air Conditioners

---

🔧 Step 7: Listen for Noises

Unusual sounds can tell you what’s wrong:

• Grinding or squealing: Indoor fan motor issue.

• Buzzing or clicking: Electrical problem.

• Rattling: Loose parts or debris in outdoor fan.

Noise troubleshooting often requires tightening screws, clearing obstructions, or in some cases, calling a pro.

---

🧊 Step 8: Refrigerant & Professional Issues

If none of the above fixes work, you may have a deeper issue:

• Low or leaking refrigerant

• Faulty sensors or control board

• Bad compressor or fan motor

These require a licensed HVAC technician—don’t attempt refrigerant work yourself.

Reference: EPA – Refrigerant Handling Rules

---

📝 Troubleshooting Quick Reference Chart

---

💡 Preventing Future Problems

Regular maintenance keeps most issues away:

• Clean filters monthly

• Inspect coils quarterly

• Flush drain line every season

• Keep outdoor unit clear of debris

• Schedule pro servicing every 2–3 years

Reference: ENERGY STAR – HVAC Maintenance

---

✅ Conclusion: Mike’s Take

Most of the time, your MRCOOL Advantage not cooling or heating comes down to simple fixes—filters, coils, drain lines, or settings.

My rule of thumb:

1. Start with easy DIY checks.

2. Use the error codes as clues.

3. Call a pro only if it’s a refrigerant or major electrical issue.

With a little routine care and troubleshooting know-how, you’ll keep your system running smoothly and avoid costly breakdowns.

---

In the next topic we will know more about: Heating Performance in Winter: Can the MRCOOL Advantage Keep Your Room Warm?