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Detailed homeowner guides explain safe checks, possible causes and when to request professional diagnosis.
Search what you observe—not what you think the failed part is. Several HVAC faults can produce the same symptom, and an on-site diagnosis is often needed before choosing a repair.
615 matching answers · page 2 of 21
In many split systems the furnace provides heat in winter and its blower also moves air across the indoor AC coil during cooling season.
SEER2 is a seasonal cooling-efficiency rating used for central air conditioners and heat pumps. A higher rating indicates greater rated cooling efficiency under the test procedure, but actual utility costs also depend on climate, installation, usage and rates.
HSPF2 is a seasonal heating-efficiency metric for heat pumps. Higher values indicate better rated heating efficiency, but real-world performance also depends on climate, controls, sizing and installation.
BTU is a unit of heat energy. HVAC capacity is often described in BTU per hour; for air conditioning, 12,000 BTU/h is commonly called one ton of cooling capacity.
A ton is a cooling-capacity term, not equipment weight. One ton corresponds to about 12,000 BTU per hour of cooling capacity.
Variable-speed or variable-capacity equipment can adjust output instead of operating only at full capacity. That can improve temperature control, sound levels and part-load efficiency when the system is properly selected and installed.
Two-stage equipment has a lower and a higher operating stage. It can spend more time at reduced output than a single-stage system, which can improve comfort and reduce cycling in suitable applications.
A ductless mini-split is a heat-pump or air-conditioning system that connects one or more indoor units to an outdoor unit without conventional central ductwork.
A zone is an area of a building controlled separately from other areas, using separate indoor units or duct dampers and controls. Proper design is important so airflow remains within equipment requirements.
A return-air grille pulls room air back toward the HVAC equipment so it can be filtered and conditioned again. Blocking return airflow can reduce system performance.
Start with safe basics: confirm the thermostat is in cooling mode, the setpoint is below room temperature, and the filter is not heavily clogged. If airflow is present but the home still does not cool, refrigerant, coil, compressor, electrical or airflow problems may require a technician.
Warm air can come from an incorrect thermostat setting, restricted airflow, an outdoor-unit problem or a refrigeration issue. Check the thermostat and filter; refrigerant and electrical diagnosis should be left to a qualified HVAC technician.
Weak airflow can be caused by a dirty filter, blocked return/supply grilles, blower problems or duct restrictions/leaks. If a clean filter and open registers do not restore airflow, professional airflow and static-pressure testing is appropriate.
A frozen coil can be associated with restricted airflow or a refrigeration problem. Turn off cooling, avoid continuing to run a frozen system, check the filter, and arrange service if icing returns.
Frequent short cycling can be related to controls, airflow, electrical issues, refrigerant conditions or equipment sizing. Because repeated cycling can stress components, persistent short cycling should be diagnosed professionally.
Long runtime may be normal during extreme heat, especially for variable-capacity systems, but it can also indicate a dirty filter, airflow loss, duct leakage, low capacity, refrigeration problems or a building-load issue. Compare comfort and indoor temperature, not runtime alone.
Check the thermostat setting and whether a breaker has tripped. Do not repeatedly reset a breaker; if it trips again or the outdoor unit remains off, electrical diagnosis should be handled by a technician.
A breaker that repeatedly trips can signal an electrical or equipment fault. Do not keep resetting it; turn the system off and have the circuit and HVAC equipment inspected.
Cooling systems produce condensate. Water near the unit can result from a blocked drain, drain-pan issue, frozen coil or other moisture problem; shut down cooling if water threatens ceilings, electrical components or property, then arrange service.
Some operating sound is normal, but a new loud buzz or hum can indicate electrical, motor, compressor or control issues. If the sound is severe, accompanied by burning odor, or the system is not operating normally, turn it off and request service.
Rattling can come from loose panels, debris, duct vibration or mechanical components. If tightening an accessible loose panel is not clearly the issue, a technician should inspect the system before damage progresses.
A musty odor can point to moisture, dirty components or microbial growth. The underlying moisture source should be corrected; filtration or duct cleaning alone does not solve an active moisture problem.
Uneven temperatures can come from solar gain, insulation, room load, airflow imbalance, duct leakage, return-air limitations or system design. Closing registers is usually not a substitute for diagnosing the airflow and load.
Yes. A heavily loaded filter can restrict airflow, reduce capacity and contribute to coil icing or equipment shutdown. Replace the filter with the correct size and an efficiency level the system can accommodate.
A furnace not blowing heat may be circulating cool air between heating cycles, have restricted airflow, or have an equipment or safety-control fault. First distinguish cold airflow, little or no airflow, and heat that starts then stops. Check Heat mode, a setpoint above room temperature, the fan setting, and an accessible filter according to the equipment manual. Keep grilles clear and equipment panels secured. Do not open electrical or burner panels, repeatedly reset breakers, or bypass safety devices. Persistent no-heat operation requires professional diagnosis. If you suspect a gas leak or receive a carbon monoxide alarm, leave the area and contact emergency services from a safe location; do not wait for a routine appointment. Heco's full Furnace Not Blowing Heat guide explains the next steps.
Read the detailed Furnace Not Blowing Heat guide →
No. Refrigerant work requires appropriate equipment, training and EPA certification requirements. Low refrigerant also often means a leak or another condition that should be diagnosed rather than simply topped off.
If the heater is not working in your house, first identify whether your home uses a furnace or heat pump, then describe the problem: nothing starts, air blows but feels cool, heat stops repeatedly, or some rooms stay cold. “Not working” does not identify a particular failed part. A working fan or a Heat symbol on the thermostat does not by itself confirm that the home is receiving heat. Check the thermostat's normal user settings and schedule. Follow the system instructions for accessible filter inspection and keep return/supply grilles clear. Avoid opening equipment, adjusting wiring or refrigerant, forcing a defrost cycle or defeating safety controls. If the system cannot maintain the requested temperature, remains unresponsive or repeatedly stops, arrange a professional evaluation. When contacting Heco, include your city/ZIP, equipment type if known, thermostat message and when the problem started. Mention any urgent occupant needs so availability can be reviewed; a request does not confirm an appointment. For a gas odor or CO alarm, leave and contact emergency services from a safe location. Call (916) 813-2766, daily 8 AM–7 PM. The $49 repair service fee is for first-time customers only; repairs are charged separately after approval.
Read the detailed Why Is My Heater Not Turning On? guide →
Check that the thermostat is set to Heat and the fan is on Auto rather than continuously On. A dirty filter can also cause overheating and safety shutdowns; persistent cold-air operation needs professional diagnosis.
If your furnace will not start, it may be because the thermostat is not requesting heat, power is unavailable, the system is in a protective delay, or an equipment/safety-control fault has interrupted startup. Start with Heat mode, a setpoint above room temperature and any schedule or away setting. Follow your thermostat manual for user-replaceable batteries and normal startup timing. Notice which symptom applies: a blank thermostat, a silent furnace, equipment running without warm air, or heat that starts then stops. These conditions need different checks; none proves that a thermostat, igniter or motor has failed. Inspect only an accessible filter and clear grilles as the equipment instructions allow. Leave panels secured. Do not touch wiring, relight burners, bypass safety switches or repeatedly reset breakers. If it still will not start, request diagnosis and report your observations. For a gas odor or CO alarm, leave and contact emergency services from a safe location instead of waiting for an appointment. Read Heco's detailed no-start guide or call (916) 813-2766. The $49 repair service fee applies to first-time customers only; repair charges are separate.
Read the detailed Why Is My Heater Not Turning On? guide →
Short cycling can be caused by thermostat issues, restricted airflow, overheating, flame-sensing or other control problems. Replacing a dirty filter is a safe first step; recurring cycling should be inspected.
Equipment condition still requires professional evaluation. For regulations, rebates and efficiency guidance, Heco checks authoritative sources and identifies items that can change.
Tell Heco the symptom, equipment type, property type and location. We will help identify the next practical step.