By AMZ Appliance Repair | Buffalo Grove, IL | Open 7 Days | (773) 822-1610
It’s the middle of summer, your AC is running, and your house is still hot. The unit is on, the fan is blowing — but nothing is cooling down.
Here in Buffalo Grove and the northwest suburbs of Chicago, we know how brutal the summer heat gets. When your AC stops keeping up, it’s not just uncomfortable — it can be dangerous, especially for kids, elderly family members, and pets. This is one of the most common calls we get at AMZ Appliance Repair during June, July, and August.
The good news: some causes are simple fixes you can do yourself in 10 minutes. Others need a licensed technician. Here’s how to tell the difference — and what to do about each one.
1. Your Air Filter Is Clogged
This is the number one reason ACs stop cooling effectively — and the easiest to fix.
A dirty filter blocks airflow through your system. When air can’t move freely, your AC can’t push cold air through your home efficiently. It runs and runs and nothing gets cool. If you haven’t replaced your filter in the last 1 to 3 months, start here before anything else.
What to do: Turn off your AC at the thermostat. Find the filter — it’s usually near the air handler unit or at the return air vent on the wall or ceiling. Pull it out. If it looks gray and clogged with dust, replace it. Filters cost $5 to $20 at any hardware store. Turn the AC back on and give it 30 minutes.
You’d be surprised how often this is the whole problem.
2. Your Thermostat Settings Are Off
Before you call anyone — double check your thermostat.
It sounds obvious, but it’s more common than you think, especially after a power outage or if someone else in the house touched the settings. Make sure it’s set to Cool and not Fan Only or Heat. Set the target temperature at least 5 degrees below the current room temperature so the system actually kicks into a full cooling cycle.
If you have a smart thermostat, check that it hasn’t been accidentally reprogrammed or put into an energy-saving mode that’s holding the temperature higher than you want.
3. The Outdoor Unit Is Dirty or Blocked
Your AC system has two parts — the indoor air handler and the outdoor condenser unit. The outdoor unit pulls heat out of your home and releases it outside. If it’s surrounded by leaves, grass clippings, dirt buildup, or overgrown shrubs, it can’t do its job — and your home stays warm no matter how long the system runs.
What to do: Turn the AC off at the thermostat first. Walk outside and look at the condenser unit. Clear away any debris around it — you want at least 2 feet of clear space on all sides. If the metal fins look clogged with dirt, gently rinse them with a garden hose, spraying from the inside out. Let it dry completely before turning the system back on.
Do not use a pressure washer. It will bend the fins and damage the unit.
In Buffalo Grove and the surrounding suburbs, cottonwood season in late spring can clog outdoor units fast. If you haven’t cleaned yours since last year, it’s worth checking.
4. You’re Low on Refrigerant
Refrigerant is the chemical that actually makes your air cold. Without enough of it, your AC runs constantly but never cools the house down — the air coming from the vents might feel slightly cool but never truly cold.
Signs your system is low on refrigerant:
- Ice forming on the copper lines running to the unit or on the indoor coil
- A hissing or bubbling sound near the outdoor unit
- The AC runs all day but the house never reaches the set temperature
- Your electricity bill is higher than normal
Here’s the important thing to understand: refrigerant doesn’t get “used up” on its own. If you’re low on refrigerant, it means there’s a leak somewhere in the system. Simply recharging it without finding and fixing the leak is a temporary fix — it’ll be low again within weeks or months.
This is not a DIY repair. A licensed HVAC technician needs to locate the leak, repair it, and then recharge the system properly. Call AMZ Appliance Repair at (773) 822-1610 and we’ll diagnose it the same day.
5. The Evaporator Coil Is Frozen
If you see ice forming on your indoor unit or on the copper refrigerant lines running from it, your evaporator coil has frozen over. This happens when airflow is restricted — usually from a dirty filter — or when refrigerant levels are low.
A frozen coil can’t absorb heat from the air, so even though the system is running, it’s not cooling anything.
What to do: Turn the AC completely off and switch the fan setting to On (not Auto). This circulates warm air over the coil and helps it thaw. Depending on how frozen it is, this can take anywhere from 2 to 24 hours. Place towels around the indoor unit to catch drips. Replace the air filter while you’re waiting.
Once it’s fully thawed, turn the AC back on and monitor it. If the coil freezes again within a day or two, there’s an underlying problem — low refrigerant, a failing blower motor, or restricted ductwork — that needs a professional diagnosis.
6. Your AC Is Undersized for Your Home
If your AC has always struggled on hot days — even when everything seems to be working correctly — the unit may simply be too small for your square footage.
An undersized AC will run non-stop, never quite reach the set temperature, wear out its components faster, and drive up your electricity bill. This is especially common in older Buffalo Grove homes where the original AC was installed decades ago and may not account for additions, finished basements, or sunrooms added since then.
A proper “load calculation” done by a licensed HVAC technician determines the right size unit for your specific home based on square footage, insulation, windows, sun exposure, and local climate. If your system is genuinely too small, no amount of maintenance will make it keep up on a 95-degree Chicago summer day.
7. There’s an Electrical or Mechanical Problem
If you’ve checked everything above and the AC still isn’t cooling, the problem is likely internal — and it needs a professional.
Common mechanical issues we diagnose and repair at AMZ include:
- Failed capacitor — the capacitor starts the compressor and fan motors. When it fails, the unit may hum but not cool. This is one of the most common AC repairs and usually affordable.
- Bad contactor — the contactor controls power to the compressor. When it fails, the outdoor unit won’t run at all even though the indoor fan is blowing.
- Compressor failure — the compressor is the heart of the AC system. When it fails, there’s no cooling at all. This is the most expensive repair — sometimes the cost points toward a new system instead.
- Ductwork leaks — if your ducts have gaps or cracks, cooled air is leaking into your walls and attic instead of reaching your rooms. You may notice some rooms cool fine while others stay warm.
These issues all require proper diagnostic equipment to identify. Attempting to diagnose or repair them without the right tools can make the problem worse.
When to Call a Professional?
You can handle a clogged filter, a blocked outdoor unit, or a thermostat setting yourself. But if you’ve gone through all of those and your AC still isn’t cooling — it’s time to call a licensed technician.
Waiting usually makes it worse. A small refrigerant leak becomes a damaged compressor. A minor electrical issue becomes a full system failure on the hottest day of the year. In Buffalo Grove summers, that’s not a situation you want to be in.
AMZ Appliance Repair offers same-day AC repair 7 days a week — including weekends — across Buffalo Grove, Wheeling, Lincolnshire, Riverwoods, Arlington Heights, Long Grove, and surrounding Lake County and Cook County areas.
📞 Call us now: (773) 822-1610 🗓️ Or book online: amzappliancerepair.com/buffalo-grove/hvac-repair/ac-repair/
We’ll come out, find the problem, and give you a straight answer on what it costs before we touch anything.
