Why Is My AC Not Cooling My House?
It’s the middle of summer, your AC is running, but your house just won’t cool down. Sound familiar? You’re not alone — this is one of the most common calls we get at AMZ Appliance Repair in Buffalo Grove, IL.
The good news: some causes are simple fixes you can do yourself. Others need a professional. Here’s how to tell the difference.
1. Your Air Filter Is Clogged
This is the #1 reason ACs stop cooling effectively — and the easiest to fix.
A dirty filter blocks airflow, which means your AC can’t push cold air through your home efficiently. If you haven’t changed your filter in the last 1–3 months, that’s likely your problem.
What to do: Turn off your AC, locate the filter (usually near the air handler or return vent), and replace it with a new one. Filters cost $5–$20 at any hardware store. Turn the AC back on and wait 30 minutes to see if cooling improves.
2. Your Thermostat Is Set Wrong
Before anything else — double check your thermostat settings.
– Make sure it’s set to “Cool” (not “Fan Only” or “Heat”)
– Set the temperature at least 5 degrees below the current room temperature
– If you have a smart thermostat, check that it hasn’t been accidentally reprogrammed
This sounds obvious, but it’s surprisingly common — especially after a power outage or if someone else in the house adjusted the settings.
3. The Outdoor Unit Is Dirty or Blocked
Your AC has two parts: the indoor air handler and the outdoor condenser unit. If the outdoor unit is clogged with dirt, grass clippings, or debris, it can’t release heat properly — and your home won’t cool down.
What to do:
– Turn off the AC at the thermostat
– Check for leaves, debris, or overgrown plants around the unit (keep at least 2 feet of clearance on all sides)
– Gently rinse the condenser coils with a garden hose (spray from the inside out if possible)
– Let it dry, then turn the AC back on
Do NOT use a pressure washer — it can damage the fins.
4. Your AC Is Low on Refrigerant
Refrigerant is the chemical that actually cools the air inside your system. If your AC is low on refrigerant (also called Freon), it will run constantly but never get your house cold.
Signs of low refrigerant:
– Ice forming on the refrigerant lines or indoor coil
– Hissing or bubbling sound near the unit
– AC runs all day but the house stays warm
Important: Refrigerant doesn’t “run out” on its own — low refrigerant means there’s a leak somewhere in the system. This is not a DIY fix. A licensed HVAC technician needs to find the leak, repair it, and recharge the system.
5. The Evaporator Coil Is Frozen
If you notice ice on your indoor unit or the copper lines running from it, your evaporator coil may be frozen. This happens when airflow is restricted (often from a dirty filter) or when refrigerant is low.
What to do:
– Turn the AC off and switch the fan to “On” to help it thaw (this can take 2–24 hours)
– Replace the air filter
– Once thawed, turn the AC back on
If it freezes again quickly, call a technician — there’s an underlying problem that needs to be fixed.
6. Your AC Is Too Small for Your Home
If your AC has always struggled to keep up on hot days — even when everything is working correctly — it may simply be undersized for your square footage.
An undersized unit will run constantly, wear out faster, and never fully cool your home. A technician can do a “load calculation” to determine the right size for your space.
When to Call a Professional?
You can handle a clogged filter or a blocked outdoor unit yourself. But if you’ve checked those and your AC still isn’t cooling, it’s time to call in an expert. You likely have one of these issues:
– Refrigerant leak
– Frozen evaporator coil (recurring)
– Compressor failure
– Electrical or capacitor issue
– Ductwork problems
Delaying repairs usually makes things worse — and more expensive.
