HVAC troubleshooting
Common HVAC Problems and What They Can Mean
Begin with the symptom. Each guide gives a quick answer, the usual causes, checks a homeowner can safely make and the signs that it is time for a professional.
Cooling problems
- AC Not CoolingAn air conditioner that runs without cooling the house is most often choked by a dirty filter, set to the wrong mode, or fighting an outdoor unit packed with leaves and grass.
- AC Blowing Warm AirWarm air from the vents usually tells you the inside fan works but the condenser in the yard has stopped pulling heat out.
- AC Freezing UpIce forms once the indoor coil drops below freezing, which tends to happen because not enough warm air is passing over it or the refrigerant charge is low.
- AC Leaking WaterAir conditioners pull moisture out of humid air, and that water normally drains away through a pan and a small pipe.
- AC Making NoiseWhat the noise sounds like says a lot.
- AC Not Turning OnWhen an AC will not start at all, the usual causes include drained thermostat batteries, a wrong mode, a breaker that tripped, an outdoor disconnect left off, a float switch reacting to a backed-up drain, or a failed control board or capacitor.
Heating problems
- Furnace Not HeatingA furnace that won't heat is often held back by a thermostat setting, a dirty filter, a tripped breaker or switch, or a furnace door that isn't fully closed.
- Furnace Blowing Cold AirCool air from a furnace can be as simple as the fan set to On, so the blower runs between heating cycles, or the first moments before the burners warm up.
- Heat Pump Not HeatingA heat pump may feel like it isn't heating because it delivers gentler warmth than a furnace, runs a defrost cycle in cold weather, or leans on backup heat during a cold snap.
A gas smell, an electrical or burning odor, smoke, or a carbon monoxide alarm. For gas or CO, get everyone out and call 911 or the gas utility from outside. Losing cooling during extreme heat is also urgent when infants, older adults or anyone with a health condition live in the house.
Outdoor units and furnaces hold high voltage, capacitors that keep a charge after power is off, gas valves and pressurized refrigerant. Looking, listening and noting details is safe, and it gives the provider useful information.
On an air conditioner in summer, no; ice points to an airflow or refrigerant issue. A heat pump in winter is different, since a thin layer of frost that melts off during a defrost cycle is expected.
When it began, what the system does and doesn't do, any noises or smells, whether a breaker tripped, and roughly how old the equipment is. A photo of the outdoor unit's data plate can help as well.
Call now
Still not sure what's wrong?
Call and describe the symptom. A local HVAC provider can help work out what is going on and how urgent it is.
CALL NOW[TRACKING_NUMBER]For homeowners who need a new HVAC or AC service: repair, replacement or installation. The line can't help with billing or existing-customer service.