The heating and cooling questions we hear most from homeowners around Troy and the Miami Valley. Plain answers, what you can check yourself, and when it is time to call.
Written by Legacy Heating and Air · Updated October 2026
Why is my AC running but not blowing cold air?
The usual causes are a clogged filter, a frozen indoor coil, an outdoor unit that has lost power, or low refrigerant from a leak.
Before you call, a few checks take five minutes and sometimes solve it:
✓Thermostat set to Cool, fan set to Auto. "On" just moves room air around, even when the AC is off.
✓Replace the filter if it looks gray or matted. A choked filter is the most common cause of weak cooling.
✓Walk outside. If the big fan on the outdoor unit is not spinning, check the breaker and the disconnect box on the wall next to it.
✓Look for ice on the copper line or the indoor coil. If you see it, switch the system off and set the fan to On so it thaws. Running a frozen system can ruin the compressor.
If none of that fixes it, it is time for a technician. Refrigerant does not get used up. If it is low, there is a leak, and topping it off without finding the leak only buys a few weeks.
Why is my furnace not heating, or blowing cold air?
A thermostat setting, a dirty filter, or a tripped safety switch is behind a surprising number of no-heat calls.
Run through these first:
✓Thermostat on Heat, set a few degrees above room temperature, with fresh batteries.
✓Fan on Auto. With the fan on "On", it blows room-temperature air between heating cycles, which feels like cold air.
✓Change the filter. A clogged filter makes the furnace overheat, and a safety switch shuts the burners off. The tell is a furnace that starts, runs a few minutes, and quits.
✓Check the furnace power switch (it looks like a light switch on or near the unit) and the breaker.
✓High-efficiency furnaces have white plastic vent pipes that exit the side of the house. Snow, ice, or a bird nest blocking them will shut the furnace down.
✓Make sure the furnace door is seated. A loose panel trips a safety switch and nothing will run.
Past that, the common culprits are a dirty flame sensor, a failed igniter, or a clogged condensate drain, all quick fixes for a technician. If you ever smell gas, leave the house first, call your gas utility from outside, and do not flip any switches on the way out.
How much does a new furnace or air conditioner cost?
It depends on the size your home needs, the efficiency level you choose, and what has to change around the equipment, which is why we price every job in writing after seeing the house, and the estimate is free.
National averages you see online are not much help, because the spread between two houses on the same street can be thousands of dollars. These are the things that actually move the number:
✓Size. A bigger home or a leakier one needs more capacity.
✓Efficiency and comfort level. Single-stage equipment costs the least. Two-stage and variable-speed systems cost more up front, run quieter, hold temperature more evenly, and use less energy. In Ohio, new central air conditioners must be at least 13.4 SEER2 and heat pumps at least 14.3 SEER2.
✓One system or both. Replacing the furnace and AC together usually costs less than doing them a few years apart, since the labor overlaps.
✓What surrounds the equipment. Undersized or leaky ductwork, a new electrical circuit, gas line work, or venting changes (going from an older furnace to a high-efficiency one means new plastic vent pipes) all add to the job.
✓The refrigerant change. New air conditioners and heat pumps use new refrigerants (more on that below), and they cost somewhat more than the units they replaced.
When you compare quotes, compare the same efficiency level and ask what is included: haul-away of the old unit, permits where required, a new thermostat, and warranty registration.
Repair it if the system is fairly young and the fix is reasonable; replace it if it is near the end of its life and the repair is a big one.
A rule of thumb many contractors use: multiply the age of the unit by the repair cost. If the answer is over about $5,000, replacement usually makes more sense. A $600 repair on a 6-year-old furnace is an easy yes. A $1,200 repair on a 15-year-old air conditioner usually is not.
Other signs it is time to replace:
✓The AC still uses R-22 refrigerant (most systems installed before 2010). R-22 has not been made since 2020, so any repair that involves refrigerant gets expensive.
✓You have paid for repairs two or three years running.
✓Energy bills keep creeping up, or some rooms never get comfortable.
✓A cracked furnace heat exchanger. That is a safety issue, and on an older furnace replacement is the right call.
We will tell you honestly when a repair is the smarter move, even when it is the cheaper answer.
A gas furnace typically lasts about 15 to 20 years, and a central air conditioner or heat pump about 10 to 15 years.
Heat pumps tend toward the shorter end because they work year-round, heating and cooling. How long any system lasts depends far more on correct sizing, a clean install, and regular maintenance than on the brand name.
Not sure how old yours is? The manufacture date is usually coded into the serial number on the unit's data plate. Send us a photo of the plate and we can tell you.
How often should I change my furnace filter?
Change a standard 1-inch filter every 1 to 3 months, and a thick 4 or 5-inch media filter every 6 to 12 months.
Change it more often if you have pets, allergies, smokers in the house, or a remodel kicking up dust. The same filter serves your furnace and your AC, so it matters year-round.
Higher rated is not always better. A very fine filter crammed into a 1-inch slot can choke airflow and make the system work harder. For most homes a MERV 8 to 11 filter is the sweet spot. When you slide the new one in, the arrow on the edge points toward the furnace.
Should I get a heat pump or a furnace in Ohio?
For most Miami Valley homes with natural gas, a gas furnace or a dual-fuel system (a heat pump paired with a gas furnace) is the best fit; homes without gas are where a heat pump really earns its keep.
A heat pump does not burn anything. It moves heat, pulling it out of the outdoor air in winter and out of your house in summer. That makes it very efficient in the mild weather that covers most of an Ohio fall and spring. As the temperature drops, its output drops too. Cold-climate models keep heating well below freezing, but on the coldest January nights a gas furnace still puts out warmer air.
A dual-fuel system gives you both. The heat pump handles cooling and the mild heating days, and the furnace takes over automatically when it gets cold enough that gas is the cheaper or more comfortable choice. Whether that pays off depends on your gas and electric rates, and we can walk through the math for your house.
For an addition, a garage, or an older home with no ductwork, a ductless mini-split heat pump is often the cleanest answer.
What is the refrigerant change, and does it affect my current AC?
Your current system can keep running and can still legally be repaired; the change only affects new equipment, which since 2025 uses lower-impact refrigerants, mostly R-454B and R-32.
What it means for you in practice:
✓The refrigerants are not interchangeable. Your existing R-410A system has to be serviced with R-410A.
✓R-410A supply is being phased down, so expect refrigerant-related repairs to cost more over the next few years. If an older system has a leak, that belongs in the repair-or-replace decision.
✓Replacing only the outdoor unit with a new-refrigerant model usually means replacing the indoor coil too, because the two have to match.
✓Systems still running on R-22 (mostly installed before 2010) are in a tougher spot. R-22 is no longer produced, and what is left is recovered and recycled stock.
Is there still a federal tax credit for a new heat pump or AC?
No, not for new installs: the federal Energy Efficient Home Improvement Credit (25C) ended for equipment installed after December 31, 2025.
If you had qualifying equipment installed during 2025, you can still claim it on your 2025 federal return using IRS Form 5695. Check with your tax preparer.
Manufacturer promotions and utility programs come and go. When we quote your system, we will tell you about anything currently available that applies to it.
How often should I have my HVAC system serviced, and is it worth it?
Once a year per system is the standard: the furnace in the fall and the air conditioner in the spring.
A tune-up catches the cheap problems before they turn into a no-heat or no-cool call on the worst day of the year. That means a weak capacitor (the most common summer failure), a dirty flame sensor, a clogged condensate drain, or a coil so dirty the system runs twice as long as it should. On a furnace it is also a safety check of the burners, heat exchanger, and venting.
Many manufacturer warranties also expect the equipment to be maintained, so keep the receipts.
Size it to your house, not to the old unit and not to square footage alone.
Insulation, windows, which way the house faces, air leaks, and ductwork all change how much heating and cooling a home needs. The unit you are replacing may have been the wrong size from day one.
Bigger is not better. An oversized air conditioner cools the house fast and shuts off before it pulls the humidity out, which leaves rooms clammy and wears the system out with constant starts and stops. An undersized one cannot keep up on the hottest and coldest days. We measure your home's actual load before recommending a size.
How do I know if my furnace is safe? What about carbon monoxide?
Put a carbon monoxide alarm on every level of the house and outside each sleeping area, test it monthly, and have your furnace inspected every fall.
Call for service right away if you notice:
✓Headaches, dizziness, or nausea that ease up when you leave the house.
✓Yellow or flickering burner flames instead of steady blue.
✓Soot or rust around the furnace or the vent pipe.
✓A CO alarm going off. Get everyone outside and call 911 or your gas utility first, then us.
If you smell gas (a rotten-egg odor), leave immediately and call your gas utility from outside. Do not use light switches or your phone inside the house.
