Why Test Your Heat Before It's Cold
DFW's fall weather is famously unpredictable. One week can bring 85-degree afternoons, and the next can drop into the 40s overnight without much warning. That sudden swing is exactly why testing your heating system in September, while the weather is still mild, is worth the 20 minutes it takes. If something is wrong, you'll have time to schedule a repair calmly instead of waking up to a cold house and an emergency call.
This test isn't a substitute for a full professional tune-up covered in our heating services, but it's a smart way to catch obvious problems yourself before the season starts.
Many DFW homes haven't run their heat at all since the previous winter, sometimes seven or eight months earlier. Components that sit idle that long, especially gas ignitors, capacitors, and reversing valves on heat pumps, are exactly the parts most likely to fail on first use. Testing now means any failure happens on a mild September afternoon instead of a genuinely cold night.
The 20-Minute Heat Test
Here's a simple process any homeowner can run:
- Set your thermostat to "heat" mode and raise the target temperature at least 5 degrees above the current room temperature.
- Listen for the system to kick on within a minute or two. A furnace should ignite with a soft whoosh; a heat pump will hum to life and the outdoor unit's fan should start spinning.
- Walk to a supply vent near the thermostat and hold your hand near it. Within 3-5 minutes for a furnace, or a bit longer for a heat pump, you should feel air that's noticeably warmer than room temperature.
- Let the system run for a full 15-20 minute cycle. It should shut off on its own once the set temperature is reached, without short-cycling (turning on and off repeatedly in quick bursts).
- Check a few rooms farthest from the thermostat to confirm heat is reaching every part of the house evenly.
If your system passes all five steps without unusual noises, smells, or delays, it's in reasonable shape heading into fall.
For gas furnaces specifically, a brief burning-dust smell in the first minute of the very first cycle of the season is normal, as dust that settled on the heat exchanger over the summer burns off. That smell should fade quickly and not return on later cycles. For heat pumps, confirm the outdoor unit's fan is spinning freely and isn't obstructed by fallen leaves or debris that accumulated over the summer, since restricted outdoor airflow reduces heating capacity just as much as it does cooling capacity.
Warning Signs to Watch For During the Test
Pay close attention to a few red flags while running this test:
- A burning dust smell that lingers beyond the first minute or two, which could indicate a bigger issue with the heat exchanger or wiring
- Weak or lukewarm airflow from vents, which often points to a failing heat pump component or a furnace that isn't igniting fully
- Loud banging, screeching, or clicking that repeats throughout the cycle
- Short-cycling, where the system turns on and off in rapid succession instead of completing a full heating cycle
- Uneven heating, where some rooms warm up quickly and others barely change, which often traces back to duct issues covered under our ductwork services
Any of these signs is worth having checked before you're relying on the system every night.
Don't Skip the Thermostat
A surprising number of "no heat" calls each fall turn out to be thermostat issues rather than furnace or heat pump problems. Before assuming the worst, confirm your thermostat's batteries are fresh, the display is responsive, and it's actually set to "heat" rather than "auto" or "cool." If you have a smart thermostat, double-check that any summer schedule or vacation mode isn't overriding your manual settings. A quick reset or reprogramming, discussed in more detail on our indoor air quality and comfort resources, solves more heating complaints than people expect.
Auxiliary and Backup Heat Deserves Its Own Check
Homes with heat pumps typically rely on electric auxiliary or emergency heat strips to supplement the system during the coldest stretches, when the heat pump alone can't extract enough warmth from outdoor air. These strips only engage under specific conditions, which means they can go unused for an entire mild winter and still be silently failing when a genuine cold snap finally demands them.
To check this, set your thermostat to "emergency heat" mode briefly, if your system has that setting, and confirm you feel a noticeable increase in warm airflow within a few minutes. Switch back to normal heat mode afterward. If your thermostat doesn't offer an emergency heat option, a technician can test the strips directly during a fall visit, since this is one of the components most likely to be overlooked in a homeowner's own DIY test.
Lessons From DFW's Unpredictable Cold Fronts
Our technicians have answered plenty of calls the morning after a surprise overnight cold front swept through the Metroplex, catching homeowners off guard. A common pattern: a heat pump that worked fine in spring gets tested for the first time in months, only for the homeowner to discover the auxiliary heat strips never kick in properly, or the reversing valve is sticking. These issues are usually simple fixes when caught early, but they turn into stressful, cold nights when discovered for the first time during an actual freeze.
We've also seen furnaces that sat unused all summer develop a stuck flame sensor from dust accumulation, causing the system to attempt ignition, fail, and lock out repeatedly. Running your own test in September, while a technician visit can still be scheduled at a normal pace, avoids that scramble.
When to Call a Professional
If your DIY test reveals weak heat, unusual smells, strange noises, or a system that won't turn on at all, it's time to call in a professional rather than troubleshoot further. Gas furnace issues in particular, like a cracked heat exchanger or ignition problems, should always be diagnosed by a trained technician rather than a homeowner, both for safety and to avoid making a small issue worse. Our team can also confirm whether a heat pump's auxiliary heat is engaging correctly, something that's difficult to verify without the right tools.
Take the Test Today
Running this simple check now, while DFW weather is still mild, gives you options. If everything checks out, you can head into fall with confidence. If something's off, you have time to get it fixed on your schedule instead of during an emergency.
Call Spencer Air Conditioning & Heating at 972-446-2665 to schedule a full inspection, or explore our maintenance plan to keep your heating system checked twice a year automatically.
Spencer Air Conditioning & Heating — Serving DFW Since 1960. License TACLA115636C