When heating or cooling stops working, it can feel urgent and stressful. This guide helps you do safe, basic checks at home. Many problems are simple fixes. Others need a licensed technician. Use the steps below to narrow the cause and avoid unneeded service fees.
Key Takeaways
- Use a room-by-room Manual J load calculation (not a square-foot rule).
- Select equipment with Manual S and verify ducts with Manual D for comfort and efficiency.
- Avoid oversizing: short-cycling wastes fuel and can create uneven temperatures.
Safety first. If you smell gas, see smoke, find melted wiring, or a carbon monoxide alarm sounds, leave the house and call emergency services. Do not try to repair gas or dangerous electrical faults yourself. For refrigerant or combustion work, hire a certified pro.
Key takeaways (N/A)
Start with three basic checks that are quick and safe for most homeowners. These checks fix many no-heat and no-cool calls. They also give useful details you can tell a technician. Keep a notepad and take photos of any error codes or visible damage.
A clear, short record of what you tried and what you saw reduces diagnostic time and can lower your bill. If you replace a filter or battery, keep the receipt. Write down any breaker resets and whether they stayed on or tripped again.
- Check thermostat mode, batteries, and setpoint first.
- Look for gas smell, CO alarm, or burning electrical odors and act immediately if present.
- Replace clogged filters and clear debris near the outdoor unit.
Finish by saving receipts and service dates. Track any error codes, sounds, or smells. Clear notes speed up diagnosis and may lower diagnostic fees when a technician arrives.
Where should I start troubleshooting?
Begin at the thermostat and move outward toward the equipment. Thermostats control the system and are often the source of failure. A wrong mode, dead batteries, or a blank screen looks like a major failure but is easy to correct. Taking a methodical approach saves time.
After the thermostat, check power at the breaker and the outdoor disconnect. Replace thermostat batteries and put in a clean air filter. Carry a flashlight and a notepad. Note lights, sounds, and any blinking error codes you see. These clues matter to the technician.
Record the order you check items. If you reset a breaker or power switch, wait a minute and watch the unit try to start. Repeated tries or immediate trips point to electrical or motor issues. If you smell anything odd or see visible damage, stop and call a pro.
Is the thermostat set correctly?
Verify the thermostat shows HEAT, COOL, or OFF. Many thermostats have separate modes for heat pump or conventional systems. Also check that the setpoint is a few degrees above room temp for heat or below for cooling. Small errors often cause confusion.
If the display is blank or shows odd characters, replace batteries first. For smart thermostats, check the app and Wi‑Fi status. Reboot the thermostat per the manual if needed. A simple reboot can restore control if the device lost communication with the system.
Are batteries or wiring at fault?
Weak batteries commonly kill thermostat displays. Put in fresh AA or AAA batteries and wait a minute for the thermostat to reboot. If the display remains blank, confirm the furnace switch at the air handler is on and check power at the main breaker.
Wiring issues cause intermittent or wrong operation. If wiring looks damaged or burned, do not touch it. Only experienced DIYers should work on wiring after turning off the breaker. If you see melted insulation, call a licensed technician immediately.
Have you checked the circuit breaker?
Open the electrical panel and look for tripped breakers. A tripped breaker often sits between ON and OFF or shows a different color. Reset by moving it fully to OFF and then to ON. Watch the system after reset to see if the breaker holds.
If a breaker trips again quickly, leave it off and call a pro. Repeated trips can indicate a shorted compressor, bad motor, or failing capacitor. Also check the outdoor disconnect next to the condenser; it can be turned off by landscaping work or pets.
Is the outdoor unit running?
When calling for cooling, the outdoor condenser or heat pump should power up. Look for the fan spinning and listen for a compressor hum. If the unit does not run while cooling is called, power and control issues are likely and need a technician.
If the fan runs but cooling is weak, indoor airflow may be poor or refrigerant might be low. Take note of whether the compressor cycles on and off or hums without starting. These are important clues for diagnosis.
Why is the condenser fan silent?
A silent fan can mean the motor is bad, the start capacitor failed, or debris has locked the blades. Turn power off at the disconnect before looking closely. A visual check may reveal leaves, sticks, or a plastic bag wrapped in the fan.
Do not force the fan blade by hand. Capacitors can hold a dangerous charge and motors may start unexpectedly. If no obvious blockage is found, call a technician to test the capacitor and motor safely.
Could a clogged air filter reduce output?
Dirty filters severely restrict airflow and reduce system efficiency quickly. Restricted airflow can make an AC blow warm air and cause furnaces to short cycle or run noisy. Replace disposable filters every one to three months in most homes.
Check pleated or high-efficiency filters monthly in dusty homes. Heavy restriction can make the evaporator coil freeze. If you see frost on indoor coils or refrigerant lines, turn off cooling and run the fan to thaw the coil. Note these symptoms for the technician.
Which HVAC system parts commonly fail?
HVAC systems have many moving and electrical parts that wear with use. Some parts, like capacitors and contactors, fail more often than others. Recognizing the common signs helps you decide whether to try simple checks or call a pro.
Other items such as blower motors, flame sensors, and control boards also wear. Heat pumps add reversing valves and defrost controls that may fail in cold weather. A technician inspects these parts and runs electrical and pressure tests to find the cause.
Routine maintenance often identifies weak components before they break. If your system is older, be ready to weigh repair costs against replacement. Sometimes replacing the whole unit gives better long-term value than repeated repairs.
When does a compressor fail?
Compressors fail from age, overheating, or running with low refrigerant. Symptoms include a humming sound without cooling, frequent breaker trips, or a burnt electrical smell. Technicians measure current draw and refrigerant pressure to confirm a bad compressor.
Replacing a compressor is an expensive repair and may push owners toward full unit replacement for older systems. Ask the technician to compare repair cost versus replacement with energy savings and warranty terms.
Why would the capacitor cause startups to fail?
Capacitors provide a start boost to motors. A failing capacitor causes fans or compressors to hum but not start. You may hear clicking or repeated attempts until the breaker trips. Symptoms often occur in hot weather when the load is highest.
Technicians test capacitors with meters and replace weak ones quickly. Capacitors store dangerous charge, so do not touch terminals. Replacing a capacitor often fixes startup problems at a moderate cost and prevents further motor stress.
How do refrigerant leaks show up?
Low refrigerant reduces cooling capacity, causes long run times, and can freeze the evaporator coil. You might hear a hissing leak or see oily spots near copper fittings. Indoor humidity may remain high despite long run times.
Only certified technicians can handle refrigerant. They will find and repair leaks, recover any remaining refrigerant, and recharge to factory specifications. Running on low refrigerant can damage the compressor, increasing repair cost.
When is a heat exchanger cracked?
A cracked heat exchanger is a safety hazard. It can let combustion gases, including carbon monoxide, mix with house air. Look for soot, rust near the burner, or an unusual flame color as warning signs.
If you suspect a cracked heat exchanger, shut off the furnace and call a pro. Technicians inspect visually and use gas analyzers to confirm. Repair costs are high and replacement is often the safer option for older furnaces.
What simple DIY fixes can I try?
Many HVAC problems are safe for homeowners to check and fix. Start with visual inspections, a fresh filter, and basic power checks. These steps fix many comfort problems and can avoid unnecessary service calls.
Always prioritize safety. Stop DIY work if you see gas, smoke, or melted wiring. Take photos and notes of each step you try. Those records help the technician diagnose the issue faster if you need service.
How to reset the thermostat?
Resetting clears minor software or communication errors. For battery thermostats, remove batteries for one minute and then reinstall. For hardwired units, turn the HVAC breaker off for 30 seconds and turn it back on. For smart thermostats, follow the manufacturer instructions.
If Wi‑Fi does not return after reset, check wiring and power. Persistent issues with a smart thermostat can indicate a weak common wire (C‑wire) or failing control board inside the air handler.
Can replacing the air filter help?
Yes. A clean filter improves airflow and system efficiency immediately. Replace disposable filters with the correct size and a MERV rating your system supports. Using too high a MERV rating can restrict airflow in older systems.
Set a calendar reminder to check the filter monthly during heavy use. A clogged filter can cause frozen coils, higher bills, and poor comfort. The low cost of filters prevents many common problems and extends equipment life.
How to clear a blocked condensate line?
Turn off power at the disconnect before working near the fan or motor. Locate the drain access and try a wet-dry vacuum at the outside drain to pull clogs out. A small cup of distilled vinegar in the drain can slow algae growth.
If the clog is not reachable or the drain keeps overflowing, call a technician. Persistent clogs can indicate a damaged trap or heavy biological growth that needs pro tools to clear and sanitize safely. (Source: ASHRAE Technical Resources)
When should I call a professional?
Call a professional when you face safety risks, cannot fix the issue with safe basic steps, or the repair requires licensed work. Gas, refrigerant, or complex electrical repairs need certified technicians. If you are unsure, err on the side of calling a pro.
If your system is old and repair costs approach replacement cost, ask the technician for both a repair and a replacement quote. That helps you decide the most cost-effective option for long-term comfort and energy savings.
What are emergency red flags?
Immediate hazards include a gas smell, carbon monoxide alarm activation, visible sparks, or a strong burning electrical odor. Sudden loss of heat or AC during extreme weather can also be an emergency if people or pets are at risk.
If you see these signs, evacuate if needed. Shut off gas or power only if you can do so safely. Call emergency services and your HVAC company. Fast action can prevent injury and property damage.
When is refrigerant handling required?
If your system shows low charge or leaks, a certified technician must handle refrigerant repairs. EPA Section 608 requires certification for recovery, repair, and recharge. DIY refrigerant work is illegal and unsafe.
A pro will locate and repair leaks, recover old refrigerant, and recharge the system to factory charge. Proper service protects the environment and prevents compressor damage caused by low refrigerant levels.
How much will common repairs cost?
Repair costs vary by part, system age, and local labor rates. Small items like filters or thermostat batteries cost under a hundred dollars. Mid-range parts such as capacitors or contactors often fall into the low hundreds.
Major items such as compressors or condensing unit replacements can run into the thousands. Ask for written estimates that include labor, parts, and warranty details before work begins. Written estimates reduce surprises.
How much does a filter or thermostat cost?
Disposable filters usually cost five to sixty dollars depending on size and grade. Basic programmable thermostats run fifty to one hundred fifty dollars. Smart Wi‑Fi thermostats are typically one hundred fifty to three hundred dollars.
Installation adds labor. Expect seventy-five to one hundred fifty dollars for a standard thermostat install. If a C‑wire or extra wiring is needed, that raises the labor cost and may require more time on site.
How expensive is a compressor replacement?
Compressor replacement is often the most expensive single repair. Costs commonly range from one thousand two hundred to three thousand five hundred dollars depending on unit size and labor difficulty. Local rates and permit needs affect the final price.
For older condensing units, full replacement may be a better long-term value. New units often improve efficiency and reliability. Get multiple quotes and compare warranties before deciding.
Get help from a local HVAC pro
When you need help, pick licensed, insured technicians who give clear pricing and written estimates. Ask about NATE certification and EPA Section 608 for refrigerant work. A good company explains repair versus replacement options clearly and provides service history documentation.
Prepare a short equipment history before the visit. Note the age of the unit, past repairs, and recent symptoms. Those details speed diagnosis and usually lower diagnostic time and fee. Keep invoices and warranty paperwork for resale value.
How to choose a licensed contractor?
Verify licenses, insurance, and local reviews before scheduling work. Ask if technicians have NATE certification and EPA Section 608 for refrigerant handling. Request references and written estimates that list parts, labor, and warranty periods.
Ask what brands of parts they use and whether they stock common replacement items. A transparent company shows trade licenses and provides a clear invoice. If you are in the Las Vegas area, consider local reputation and response time.
Why choose The Cooling Company?
For Las Vegas area homeowners who want prompt and honest service, The Cooling Company offers certified technicians and clear pricing. Technicians arrive with common parts and tools to fix many problems in one visit. We serve Las Vegas, Henderson, and North Las Vegas with same-day options for urgent calls.
We follow NATE-level practices and explain repair versus replacement choices with written estimates. If you are in Las Vegas, Henderson, or North Las Vegas and need fast HVAC service, call The Cooling Company at 17029308411. We provide licensed repairs, seasonal tune-ups, and clear warranties.
If you are outside our service area, look for NATE certification at NATE when choosing a contractor. A certified technician will follow EPA rules for refrigerant work and provide a written estimate. Local owners can call The Cooling Company at 17029308411 for prompt help and a transparent service visit.
Sources
- ASHRAE Technical Resources: ASHRAE Technical Resources
Compliance notes
- If you smell gas or hear a carbon monoxide alarm, evacuate and call emergency services first. Do not relight pilot lights or operate electrical switches if gas is present.
- Refrigerant work requires EPA-certified technicians under Section 608. Do not attempt refrigerant repairs yourself.
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Need HVAC service help in Las Vegas?
If you're facing an HVAC emergency in Las Vegas, Henderson, or North Las Vegas, The Cooling Company offers fast, reliable service from licensed technicians. We understand that heating and cooling emergencies don't wait for business hours.
Call us now at 17029308411 for emergency service. Our team is ready to help restore your comfort quickly and safely.