In Central Texas, the shift from cooling season to heating season is abrupt and unpredictable. One week you are running the air conditioner continuously, and the next week a cold front drops overnight lows into the 40s and you reach for the thermostat to switch modes for the first time since March. If your heating system has a problem, that is exactly when you find out about it.
The seasonal transition is one of the most revealing periods for an HVAC system. Problems that were invisible during summer cooling operation, including cracked heat exchangers, failed ignitors, seized gas valves, and deteriorated ductwork insulation, only become apparent when the heating cycle engages. Understanding what can go wrong during this transition, how to test your system before you need it, and what a professional HVAC evaluation covers gives you the best chance of getting through fall and winter without an unexpected heating failure.
Most Central Texas homes are served by a split-system heat pump or a gas furnace paired with a central air conditioning system. Understanding how yours operates during the seasonal transition helps you identify when something is off.
A heat pump system uses the same refrigerant cycle year-round, simply reversing the direction of heat transfer to provide heating in winter and cooling in summer. During the transition period, heat pump systems may operate in cooling mode in the afternoon and heating mode overnight as temperatures fluctuate. This is normal and is exactly what the system is designed to do.
A gas furnace paired with a central air system operates the two components independently: the air conditioning system handles cooling, and the furnace handles heating. When you switch the thermostat to heating mode in fall, the furnace engages for the first time since the previous spring. A furnace that sat idle through a Central Texas summer may have accumulated dust on the heat exchanger and burner assembly, which produces a brief burning smell the first time it fires. A smell that dissipates within a few minutes is normal. A persistent burning smell, a gas odor, or a failure to ignite are all conditions that require immediate attention.
Cracked Heat Exchanger
The heat exchanger is the component in a gas furnace that separates the combustion gases from the air that circulates through your home. Over time, the repeated thermal cycling of heating and cooling causes metal fatigue, and cracks can develop in the heat exchanger wall. A cracked heat exchanger allows combustion byproducts, including carbon monoxide, to enter the air supply and circulate through the home. This is one of the most serious HVAC safety concerns and one that a homeowner cannot detect visually without professional equipment. Any suspicion of a cracked heat exchanger should prompt an immediate professional evaluation.
Failed Ignitor
Modern gas furnaces use an electronic ignitor rather than a standing pilot light. These ignitors, typically made of silicon carbide or silicon nitride, have a finite service life and often fail after a period of inactivity. A furnace that clicks repeatedly but does not ignite, or that produces no response when heating is called for, may have a failed ignitor. Ignitor replacement is a straightforward repair for an HVAC technician but is not a DIY task due to the gas and electrical connections involved.
Dirty Evaporator Coil
The evaporator coil, located in the air handler above the furnace, removes heat and humidity from the air during cooling operation. After a full summer of use, the coil may have accumulated a layer of dust, debris, and biological growth that restricts airflow. When the system transitions to heating mode, a dirty evaporator coil reduces the efficiency of heat distribution and can cause the system to overheat and trip high-limit safety switches.
Ductwork Deterioration
Central Texas attics reach extreme temperatures in summer, and the ductwork running through the attic is exposed to those temperatures every day. Over time, the insulation wrapping on flexible ductwork deteriorates, and the duct connections at registers, plenums, and branch tees can loosen. Poorly insulated or leaking ductwork wastes a significant portion of the energy your system produces regardless of whether it is heating or cooling. Fall is a good time to have duct condition evaluated as part of an overall HVAC assessment.
Thermostat Issues
Programmable and smart thermostats sometimes require schedule adjustments as the season changes. More significantly, a thermostat that has been in service for several years may have calibration drift or component failures that produce inaccurate temperature readings or delayed response to heating calls. If your home seems slower to reach the set temperature in heating mode than it did in previous years, the thermostat is worth evaluating as part of the overall system check.
Do not wait for the first cold night to discover whether your heating system works. Test it on a mild fall day when outdoor temperatures are in the 60s or 70s, giving yourself time to address any problems before you are dealing with a cold house and a full service schedule. Set the thermostat to a temperature above the current indoor temperature in heating mode and verify that:
A professional HVAC fall tune-up typically includes cleaning the burner assembly and heat exchanger, inspecting the heat exchanger for cracks, testing ignition and safety controls, checking refrigerant levels in heat pump systems, testing electrical connections and contacts, lubricating moving components, evaluating duct condition, and replacing the air filter. Scheduling this service in September or early October, before fall demand peaks, ensures faster scheduling and gives you confidence heading into the heating season.
When you purchase a home, the HVAC system is one of the most important components of a professional home inspection. Our inspectors at Upright Professional Inspections evaluate the age, condition, and functional operation of both the cooling and heating systems, the condition of accessible ductwork, filter condition, thermostat operation, and any visible safety concerns. We note the approximate remaining service life of aging equipment so buyers can plan and budget accordingly.
If you are purchasing a home this fall in our Central Texas service area, we can help you understand the HVAC system’s condition before closing. View our sample reports to see how we document HVAC findings, or contact us to schedule today.