Quick answer
Before colder weather, check the filter, thermostat, visible vents and returns, and the area around outdoor equipment. Test the heating mode on a mild day by following the thermostat and equipment instructions. If the system makes an unusual noise, repeatedly shuts down, smells like gas, trips a breaker, or fails to provide heat, turn it off when safe and arrange service. Do not open a furnace, touch wiring or gas controls, or cover equipment to “winterize” it.
Texas weather can shift quickly. Preparing a system means knowing how it operates, keeping airflow clear, checking safety alarms, and scheduling a professional inspection when needed. The ENERGY STAR maintenance checklist recommends routine checks of filters, controls, electrical connections, and heating operation. Homeowners in San Antonio can review ASC’s heating repair information or contact the company if a problem appears.
Know what heats your home
Start by identifying the equipment. A gas furnace burns fuel and vents combustion byproducts outdoors. An electric furnace uses resistance heat. A heat pump transfers heat from outdoor air into the home in winter and reverses direction for cooling. Some homes combine a heat pump with a gas furnace as a dual-fuel system. Thermostat controls and maintenance differ among these designs.
Look for the model label on an exterior panel or use your installation paperwork. Do not remove a panel to find it. If you cannot tell what type you have, note the model number from a safe location or ask the service company. This is useful when checking the right filter, thermostat settings, and manufacturer’s maintenance instructions.
For a general comparison of heating choices, see furnace vs. heat pump for San Antonio homes. Do not assume all systems use the same startup behavior. A heat pump may have defrost and auxiliary-heat modes, while a furnace follows its own ignition and fan sequence. The manual is the best starting point for normal operation of the specific equipment.
Check and replace the filter as needed
Find the filter slot or return grille using the equipment manual. Note the filter size and airflow arrow, then inspect the filter against the light if the manufacturer recommends that method. Replace it when loaded or at the schedule specified for the filter and household. Pets, construction dust, smoke, and continuous operation can affect how quickly a filter collects material, so a calendar alone may not tell the whole story.
Use the exact size and a filter type appropriate for the system. A filter that is too small can leave gaps; a high-resistance filter may restrict airflow if the equipment is not designed for it. If the filter cabinet is damaged, inaccessible, wet, or difficult to open, do not force it. Ask a technician to identify the correct replacement and assess the fit.
ENERGY STAR’s heating and cooling guidance suggests checking filters regularly, with monthly checks as a practical baseline during use. Follow the actual equipment and filter instructions. Replacing a filter is a maintenance step; it cannot correct a failing blower or an internal fault.
Clear supply registers and return grilles
Walk through the rooms and confirm that visible supply registers are not covered by rugs, furniture, storage bins, or curtains. Keep return grilles clear as well. The return path brings air back to the system; blocking it can affect circulation. Avoid closing many registers to force heat into one room. That can change system airflow and may make comfort worse.
Make a note of rooms that are consistently cooler or warmer. Check whether a register is closed or obstructed, but do not remove grilles or reach into ducts. Uneven temperatures can come from airflow, duct design, leaks, insulation, windows, sun exposure, or the system itself. The pattern helps a technician ask better questions.
Do not place boxes, paint, cleaning supplies, or laundry near a furnace or air handler. Keep the access path open so the equipment can be inspected. Follow manufacturer clearance requirements and local fire guidance. If stored items block a panel or fuel appliance, move them only when the area is safe and you do not need to disturb a gas connection or electrical equipment.
Test the thermostat before a cold snap
On a mild day, switch the thermostat to Heat and set a reasonable target above the current room temperature. Check that the display works, the schedule is understood, and the system responds. Some equipment includes a protective delay, so wait for the period described in its manual. Return the thermostat to the preferred schedule after confirming normal operation.
If the thermostat uses batteries, check them as directed. Review app schedules or vacation settings that might override the wall control. Do not change advanced installer settings or heat-pump balance points unless the manual specifically identifies them as homeowner adjustments. Incorrect settings can change when auxiliary heat operates.
If the system does not start, or the blower runs without heat beyond its normal sequence, do not keep raising the set point. Note the mode, target, display message, and what the equipment does. The guide to why a heater may not turn on covers the external checks homeowners can make safely.
Keep outdoor equipment clear
If you have a heat pump, look at the outdoor unit from a safe distance. Keep leaves, grass, branches, and stored objects away from the airflow openings according to the manufacturer’s clearance instructions. Do not push debris into the coil, bend fins, pour hot water on ice, or cover the unit during operation. The outdoor fan and electrical components can start unexpectedly.
After severe weather, check visually for a branch, fence panel, or other object that has fallen near the unit. If the cabinet is damaged or the coil is blocked, turn the system off if it is safe and schedule service. Do not climb onto a roof or move heavy objects near electrical lines to reach equipment.
During a defrost cycle, some heat pumps may briefly change sound or release vapor. The exact cycle varies by model. Check the manual for what to expect. Persistent ice, a unit that repeatedly stops heating, or a fault alert calls for professional attention. Avoid breaking ice with tools or running a heat pump under a cover.
Schedule professional maintenance
Before the heating season is a practical time to ask a qualified HVAC professional to inspect equipment that has not been checked, has a history of trouble, or shows a warning sign. ENERGY STAR recommends professional system checks in its maintenance checklist. A visit can include checks appropriate to the system, such as controls, electrical connections, airflow, heating operation, and safety devices.
For fuel-burning equipment, the CPSC recommends annual professional inspection of home heating equipment, chimneys, and vents in its home heating safety guidance. Ask what the inspection includes and whether combustion and venting are part of it. Do not assume a tune-up package covers every repair or every component; request the service scope in writing.
Bring the model number, recent invoices, warranty records, and a list of comfort changes. Describe noises, odors, short cycles, breaker trips, or recurring fault messages. If the equipment is operating normally, ask what routine checks are included and which homeowner tasks are safe between visits. If the technician finds a repair, request an explanation and estimate before authorizing added work.
Check carbon monoxide alarms and household safety
Test carbon monoxide alarms according to their manufacturer’s instructions and replace units at the end of their stated service life. Install alarms in the locations required by local code and the device instructions. Do not disable an alarm because it sounds inconvenient or assume that a working alarm replaces furnace maintenance.
If an alarm sounds, get everyone outside and call emergency services from a safe location. The CPSC carbon monoxide fact sheet says not to re-enter until responders say it is safe. Carbon monoxide cannot be reliably detected by smell. Headache, dizziness, nausea, weakness, confusion, or similar symptoms require immediate attention, especially when multiple people feel unwell.
If you smell gas, leave the building without using switches or open flames and contact emergency services or the gas utility from outside. Do not investigate the appliance yourself. Keep flammable materials away from heating equipment and maintain access for a professional inspection.
Prepare the household, not just the equipment
Keep the equipment manual, service contact details, filter size, and model information where household members can find them. Show adults how to change the thermostat mode and how to turn off equipment using only a switch or control identified in the manual. Children should not play near mechanical equipment. Do not teach anyone to open a furnace cabinet or reset a repeatedly tripping breaker.
If a household member depends on a stable indoor temperature, have a plan for a heating interruption. Know a safe location to go and how to contact help. Follow public safety guidance during severe weather. Never use an oven, outdoor grill, generator, or unvented fuel device to heat the home; these can create fire or carbon monoxide hazards.
Check that doors and windows close properly and address simple gaps. Keep combustion air openings and vents clear. Ask a professional before sealing around a fuel-burning appliance or modifying ductwork. Home improvements should not interfere with safe combustion or equipment airflow.
Common preparation mistakes
Covering an outdoor heat pump can trap moisture or obstruct operation if the cover is left in place. Follow the manufacturer’s instructions and never cover an operating unit. A furnace also needs specified clearances; do not wrap it in insulation or stack items against it.
Changing to a dense filter without checking the equipment can restrict airflow. Choose a compatible filter and replace it as directed. Closing multiple registers can create another airflow problem rather than solving a cold room. If comfort varies across rooms, record the pattern and ask for an assessment.
Running a system for the first time during a freezing night leaves little time to investigate an existing fault. A mild-weather test helps reveal a thermostat or startup issue before the home depends on heat. A test does not guarantee that an unexpected future failure will not occur; it simply gives time to address a known problem.
Homeowners may also mistake a maintenance reminder for a diagnosis. A dirty filter, a warning light, and a system that shuts down are different observations. Follow the manual and let a qualified technician determine whether a repair is needed. Do not clear an alert and assume the underlying condition is gone.
A practical calendar for a warm-climate winter
As cooler weather approaches, locate the manual, identify the filter, clear return grilles, inspect the thermostat schedule, and check alarms. On a mild day, run the heating mode through a normal cycle. If the system has a maintenance history, review it and arrange any due inspection before the first cold snap.
During the season, check the filter on the schedule that fits its condition and household. Keep outdoor equipment clear after leaves or storms. Notice changes in startup, cycling, sounds, smells, and room temperatures. A short note with dates can show whether a problem is recurring or tied to a particular setting.
After the season, follow the equipment manual for continued operation and filter care. Do not shut off fuel or power for an extended period unless the manufacturer or a qualified professional directs it. A heat pump may still be needed for cooling, and components can require periodic operation or service. Keep records of any repair, replacement part, or adjustment.
Prepare before the next cold spell
Check your filter, thermostat, visible airflow, alarm operation, and equipment area. If you find a fault, arrange service before depending on the system. Review ASC’s heating service and maintenance plans for current San Antonio options.
Written by Ron Carter
Owner, ASC Heating & Air
Ron Carter is the owner of ASC Heating & Air, a San Antonio heating and cooling company serving local homeowners and businesses.
Frequently asked questions
When should I schedule heating maintenance in Texas?
Follow the equipment maker’s service interval. A check before regular heating is needed can leave time to correct a problem. CPSC recommends annual professional inspection for fuel-burning home heating equipment.
Should I cover a heat pump outside?
Do not cover an operating unit. Keep its airflow openings clear and follow the manufacturer’s instructions for any seasonal cover.
How often should I check my filter?
Check it regularly while the system runs and follow its instructions. ENERGY STAR suggests monthly checks as a practical baseline; replacement timing depends on the filter, equipment, and home.
Can I test the furnace myself?
You can use the thermostat normally and inspect an accessible filter and visible vents. Do not remove panels, touch wires or gas controls, or bypass a safety switch.
What should I do if the heater fails during a cold snap?
Use only safe external checks described in the manual and request qualified service. If there is gas odor, a CO alarm, smoke, or sparking, leave and seek emergency help. Keep vulnerable occupants in a safe place.