AC Not Cooling? 7 Common Causes & Quick Fixes

It's a sweltering July day in New Jersey, and your AC is running full blast - but your home feels like a sauna. Before you panic or suffer through the heat, let's diagnose the problem. We'll cover the 7 most common causes, which ones you can fix yourself (saving $150-300), and when you need to call in the pros.

1. Dirty or Clogged Air Filter (30% of Cases)

DIY Fix - Takes 5 Minutes

This is the #1 cause and easiest fix!

Turn off your AC system
Locate your air filter (usually in return air vent or air handler)
Remove and inspect - if you can't see light through it, it's too dirty
Replace with a new filter (write the date on it)
Turn AC back on and wait 20-30 minutes

Pro Tip: In summer, check your filter monthly. New Jersey's humidity and pollen can clog filters faster than manufacturer recommendations.

2. Frozen Evaporator Coils

If you see ice on your indoor unit or copper lines, your evaporator coils are frozen. This prevents heat absorption and blocks airflow.

Temporary DIY Fix

Turn OFF your AC completely
Turn fan to "ON" (not AUTO) to help thaw coils
Check and replace air filter if dirty
Let system thaw for 2-4 hours
Once thawed, try running AC again

Important: If coils refreeze within 24 hours, you have a bigger problem (likely low refrigerant) requiring professional repair.

Common Causes of Frozen Coils:

Restricted airflow (dirty filter, closed vents)
Low refrigerant levels
Malfunctioning blower motor
Dirty evaporator coils

3. Low Refrigerant / Refrigerant Leak

Professional Repair Required

Refrigerant doesn't "get used up" - if it's low, you have a leak that needs professional repair.

Signs of Low Refrigerant:

AC blowing warm or slightly cool air
Ice buildup on refrigerant lines
Hissing or bubbling sounds from AC
Higher electric bills
AC runs constantly but doesn't cool

Cost Alert: Refrigerant recharge in NJ typically costs $200-$600 depending on the type (R-410A vs older R-22). The leak repair is additional and varies by location.

4. Thermostat Problems

DIY Troubleshooting

Ensure thermostat is set to "COOL" (not heat or fan)
Set temperature at least 5°F below room temperature
Replace batteries if applicable
Check that thermostat is level (older models)
Clean thermostat with soft brush to remove dust

When to Replace Your Thermostat:

Incorrect temperature readings (compare with separate thermometer)
AC short cycles (turns on/off frequently)
Unresponsive controls
Age over 10 years

5. Dirty or Blocked Outdoor Unit (Condenser)

DIY Cleaning

Turn OFF power to AC at breaker
Remove debris (leaves, grass) from around unit
Gently spray coils with garden hose (not pressure washer)
Trim vegetation - maintain 2 feet clearance
Let dry, then restore power

Your outdoor unit needs to breathe! In New Jersey, cottonwood seeds, grass clippings, and leaves commonly block condenser coils, reducing cooling by up to 30%.

6. Electrical Problems

Professional Repair Required - Electrical

Electrical issues are dangerous - always call a professional for these problems.

Common Electrical Issues:

Failed capacitor: AC won't start or struggles to start
Burnt contactor: Outdoor unit won't turn on
Tripped breaker: Check electrical panel
Faulty wiring: Intermittent operation

Safety First: If you smell burning or see sparks, turn off your AC immediately and call for emergency service.

7. Compressor Failure

The compressor is your AC's heart. When it fails, your system can't cool at all. This is the most expensive repair and often means it's time for replacement.

Signs of Compressor Problems:

Outdoor unit vibrates or shakes when starting
Loud grinding or screeching noises
Circuit breaker trips repeatedly
Warm air despite everything else working

Repair vs Replace Decision:

Compressor replacement costs $1,500-$2,500. If your AC is over 10 years old, replacement is often more cost-effective, especially with current rebates up to $2,000 for high-efficiency systems.

When to Call Dimatic Controls

Call us immediately if you experience:

Electrical burning smell or visible sparks
Complete system failure (nothing turns on)
Refrigerant leak signs (oil spots, hissing sounds)
Repeated freezing after thawing
DIY fixes didn't improve cooling after 2 hours

July Special: FREE Diagnostic with Any Repair

Save $89 on diagnostic fees when you approve recommended repairs. Same-day service available!

Prevent Future AC Problems

Monthly Tasks:

Check and replace air filter
Clear debris from outdoor unit
Ensure all vents are open and unblocked
Test thermostat operation

Annual Professional Service:

Clean evaporator and condenser coils
Check refrigerant levels
Test electrical components
Lubricate moving parts

Learn about our AC maintenance plans →

New Jersey AC Challenges

Our humid summers put extra stress on AC systems. Union and Essex County residents face unique challenges:

High humidity: Forces ACs to work harder, increasing wear
Cottonwood season: Clogs condenser coils quickly
Temperature swings: 90°F days followed by 70°F can confuse systems
Aging infrastructure: Older homes may have undersized systems