When the weather starts changing, it’s easy to forget that your HVAC system needs a little adjustment too. Every fall, we get calls from homeowners wondering how to switch from AC to heat without accidentally triggering an error code or blowing cold air. Trust us — it happens more often than you’d think. At C&R Services, we help families make the transition every year, and the good news is that it’s usually a simple process once you know what to check.
Understanding How Your System Switches from AC to Heat
Before you start flipping switches or pushing buttons, it helps to know what’s happening inside your system. When you switch from AC to heat, your thermostat signals your indoor and outdoor units to reverse their roles. Instead of pulling warm air out of your home, your heat pump or furnace begins generating warmth and distributing it through your ducts.
(Quick tip—many homeowners forget to change their thermostat setting from Cool to Heat. It sounds obvious, but we’ve seen seasoned homeowners miss it after a long summer.)
According to the U.S. Department of Energy, setting and programming your thermostat correctly can improve both comfort and efficiency. That means fewer surprises when temperatures swing overnight.
Step 1: Set Your Thermostat to Heat Mode
The first step in switching from AC to heat is updating your thermostat. Most modern thermostats have clearly labeled Cool, Heat, and Auto settings. If your system doesn’t respond immediately, don’t panic—it can take a minute for the system to recalibrate.
For smart thermostats, double-check your app or schedule settings to make sure the system won’t automatically revert back to cooling mode. We’ve had more than one customer think their system was broken when it was just following a programmed schedule.
Step 2: Adjust the Temperature Gradually When Going from AC to Heat
When you move your system from AC to heat, avoid setting the temperature 10 degrees higher all at once. A gradual adjustment—say two or three degrees at a time—helps the system switch smoothly and reduces strain. This small change can extend the life of your components and prevent uneven heating across your home.
Step 3: Listen and Observe After Switching from AC to Heat
Once you’ve made the switch, stand near your vents and listen. You should hear a gentle hum or soft airflow within a few minutes. If you hear metallic clanks, buzzing, or smell burning dust, don’t worry right away—some odor is normal when the heating elements warm up for the first time in months. However, if it lingers, it’s worth calling a technician to take a look.
At C&R Services, we always tell customers: trust your senses. If something sounds or smells off, there’s probably a reason.
Step 4: Check Airflow and Filters 
When you go from AC to heat, airflow becomes even more important. Dirty or clogged filters restrict warm air and can trigger system shutdowns or short cycles. Replace your filters at the start of the season or at least every 90 days.
For better indoor air quality and efficiency, most HVAC pros recommend using filters with a MERV-13 rating or higher—if your system can handle it. According to ASHRAE’s guidelines, airflow and system capacity should always be factored in when upgrading your filter.
Step 5: Test Your Heat Pump or Furnace
If your system includes a heat pump, switching from AC to heat is as simple as flipping the mode on your thermostat. The reversing valve changes direction automatically. But if you have a gas furnace, you’ll want to ensure your pilot light or ignition system is working correctly before you rely on it full-time.
We’ve had homeowners call in panic when they smell that first puff of dust burning off the coils—it’s totally normal. That smell usually disappears after a few minutes of running the heat. However, if your furnace won’t ignite or keeps blowing cold air, it’s time to schedule professional heating repair.
When to Call a Professional
If your thermostat doesn’t respond, your vents stay cold, or your breaker keeps tripping, it’s time to call for help. Sometimes, the problem is minor—like a loose wire or blocked intake. But it can also point to something more serious, such as a failed heat pump valve or dirty sensors.
C&R Services handles all types of HVAC issues, and our team can make sure your system transitions safely and efficiently between seasons.
Keep Your System Ready for Every Season
Making the switch from AC to heat isn’t complicated, but it’s one of those small tasks that can make a big difference in comfort and reliability. Your cooling system worked hard all summer, so now’s the perfect time to shift focus to heating maintenance before cooler weather sets in. And when spring rolls around again, don’t forget to schedule your AC maintenance to keep both systems running at their best year-round.
Contact C&R Services
If you’re unsure how to switch your system from AC to heat or your furnace just won’t cooperate, our team can help. We offer fast, reliable HVAC repair and maintenance throughout East Texas. Call (903) 204-7571 or schedule your appointment online today. Stay comfortable through every season with C&R Services.
Frequently Asked Questions
Switching from AC to heat is a small seasonal task that saves big in comfort and peace of mind. And when in doubt, don’t hesitate to call C&R Services. We’re your trusted HVAC experts in Tyler and throughout East Texas. We’re here to make sure your system transitions smoothly and keeps your home comfortable year-round.
Still have questions about switching from AC to heat? Here are a few common ones we hear from homeowners every fall:
Check your thermostat settings first—make sure it’s set to Heat and not Auto. If it still doesn’t respond, the thermostat wiring or control board may need attention.
Yes, a brief burning-dust smell is normal after months of disuse. If it lasts longer than an hour, schedule a professional inspection to ensure there’s no electrical issue or debris in the ducts.
Ideally, twice a year—once before cooling season and once before heating season. Preventative maintenance keeps your system efficient and extends its lifespan. Why Won't My Thermostat Switch from AC to Heat?
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