When the temperature outside hits 95 °F in Woodbridge or Dumfries and your air conditioner suddenly starts blowing warm air, the panic is real. At All Year Appliance & HVAC Services, this is the #1 emergency call we receive from May through September across Prince William County.
These are the seven most common reasons we find—and exactly how we fix them.
1. Thermostat Set Wrong or Malfunctioning
Check first:
- Make sure thermostat is set to COOL and AUTO (not ON).
- Lower the set-point 5 °F below current room temperature.
- Replace batteries in non-wired thermostats.
- If you have a smart thermostat, reboot it by removing it from the wall for 30 seconds.
2. Dirty or Blocked Air Filter
A clogged filter is the single most common cause in Northern Virginia homes. With our high pollen and construction dust, even new filters clog in 30–45 days. Fix: Replace with a clean pleated filter (MERV 11 or higher). Airflow usually returns within minutes.
3. Outdoor Unit Not Running
Walk outside and listen:
- Fan spinning but compressor silent = possible bad capacitor or contactor.
- Nothing running at all = tripped breaker, blown low-voltage fuse, or failed transformer.
4. Frozen Evaporator Coil (Feels Like Warm Air)
Look inside the return vent or furnace panel: if you see ice or frost on the large coil or suction line, the system is frozen. Common causes: low refrigerant, dirty filter, or failed blower motor. Fix: Turn system to OFF, fan to ON, and let ice melt completely (2–4 hours) before restarting.
5. Low Refrigerant (Most Common Professional Fix)
A slow leak over the years drops refrigerant pressure. The coil gets too cold, freezes, and airflow across it becomes warm. You will usually notice the large copper line outside has frost or ice halfway back to the compressor. This requires EPA-certified recovery, leak repair, and recharge.
6. Blocked or Dirty Condenser Coils Outside
Grass clippings, cottonwood from the Potomac, and dust cake the outdoor unit within one season. Fix: Gently rinse coils with a garden hose from the inside out (never high-pressure). Remove grass and debris from fins.
7. Failed Capacitor, Contactor, or Compressor
Capacitors (round or oval silver cans) are the #1 part we replace in Northern Virginia summers. When they fail, the compressor or outdoor fan will not start. Signs: loud humming from outdoor unit but no movement, or a distinct “click-hummmm-click” every few minutes.
Quick Checklist You Can Do Right Now
- Change the air filter
- Verify thermostat settings and batteries
- Check both breakers for the outdoor unit
- Clear debris around the outdoor unit (2-foot radius)
- Look for ice on the large copper line
If the problem remains after these steps, it is time for professional diagnosis.
We carry capacitors, contactors, refrigerant, and leak-detection equipment on every truck for same-day repair in Woodbridge, Dumfries, Montclair, Lake Ridge, Dale City, and all surrounding areas.
Contact All Year Appliance & HVAC Services at 703-955-4135 anytime—24 hours a day, 7 days a week. We answer the phone even at midnight when your AC decides to blow warm air.
All Year Appliance & HVAC Services Keeping Northern Virginia cool when it matters most.