Do the AC and furnace work together?

Author: Alyce Walker V  |  Last update: Saturday, August 2, 2025

Furnaces And Air Conditioners Are Different Systems Both your furnace and your AC use ducts and vents to circulate air throughout your home. These systems are tied together because they use the same infrastructure. However, they still operate independently of each other.

Will a furnace work if the AC is broken?

Yes... your gas furnace will work just fine without the condenser. Insulate the wiring with tape. If you plan to reuse those copper lines... plug them as best you can.

Does your AC run through your furnace filter?

Air Filters

Even though the furnace is not producing any heat while operating the a/c, it still delivers the cold air throughout your home with the same blower, and passing through the same air filter. This is why, regardless of the season, you should regularly change your air filters.

Does AC and heat use the same blower?

Both AC and furnace use the same thermostat to activate and shut down. The AC and the furnace use the same blower to spread cool and warm air throughout your home.

Does my furnace affect my air conditioner?

In other words, your central AC is independent of your furnace. The outdoor unit isn't connected to the furnace at all — but they both use the same distribution system (vents, plenums, and ducts) to cycle cool air into your home.

Understanding how your AC, heat pump, and furnace work together.

Do furnace and AC work together?

Furnaces And Air Conditioners Are Different Systems

Both your furnace and your AC use ducts and vents to circulate air throughout your home. These systems are tied together because they use the same infrastructure. However, they still operate independently of each other.

Does the furnace control the AC unit?

Your furnace and your air conditioning system are two central components of your HVAC system, connected and controlled for greater efficiency. During warmer weather, you'll need to turn off your furnace and use your air conditioner instead. Your central air conditioning system is independent of your furnace.

Why does my AC work but my heat doesn't?

If your thermostat isn't set correctly, it can cause your HVAC system to blow cold air even in the winter. If your furnace filter is clogged, it can restrict airflow, causing the furnace to overheat and shut down the heating element. The blower stays on to cool down the furnace, leading to cold air circulating.

How much is an air conditioner and furnace combo?

The cost of a new HVAC system together costs $7,500 on average, usually somewhere between $5,000 to $12,500. This can end up being cheaper than replacing your AC and Furnace separately over time. Replacing your AC and furnace at the same time will enhance the performance of both while consolidating labor costs.

Why does the furnace run when the AC is on?

Incorrect Wiring

If you recently had a new HVAC unit installed, the technicians may have incorrectly wired your new system. This incorrect wiring could be causing your air conditioner and heater to come on at the same time. This may also be the case if you replaced your thermostat recently.

Do the furnace and AC use the same filter?

While many people refer to air conditioning and furnace filters as if they're different, this is not the case. Your furnace and your air conditioning system use the exact same filter, so there's no need to worry about purchasing separate filters for each piece of equipment.

Can I run my AC without a furnace filter?

The short answer: You can get away with running your AC without a filter for a short period of time. However, doing so for longer than 6-8 hours can hurt your system and decrease your home's indoor air quality.

How often should I replace my furnace filter?

Our standard recommendation is as follows:
  1. For 1- to 2- inch filters, replace them every 1 to 3 months.
  2. For 3- to 4- inch filters, replace them every 6 to 9 months.
  3. For 5- to 6- inch filters, replace them every 9 to 12 months.

Does homeowners insurance cover furnace and AC?

Homeowners insurance covers HVAC systems when the damage is a result of a covered disaster or peril, including high winds, fallen trees, theft, hail or even a fire.

Are AC and furnace on the same breaker?

If the home includes an electric furnace, that unit will also have its own dedicated breaker. Issues such as low airflow due to a clogged air filter, obstructed air vents in rooms, a failing blower motor, or internal electrical defects inside the unit may be the cause of breaker trips.

Do I have to replace my air conditioner and furnace at the same time?

Air conditioners and furnaces over 10 years old are generally what the HVAC industry would classify as “older.” This is also when most indoor and outdoor units stop being under warranty. If both your AC and furnace are more than 10 years old, we would recommend replacing them both at the same time.

How much should I expect to pay for a new furnace and air conditioner?

You can typically expect to pay between $5,000 and $15,000 for a new furnace and AC system in your home. Units with higher efficiency may have a higher initial cost but can result in significant savings on energy bills over time.

Is it cheaper to replace furnace and AC together?

You'll be happy to hear that while your exact cost savings will vary based on the systems that you choose to install, we've estimated that bundling furnace and AC installations will save you an average of $2,000 and $5,000.

How much is labor to install an AC unit?

HVAC Pro Cost

Most people pay $500 to $2,500 in labor for AC replacement.

Who to call if the furnace isn't working?

If your furnace's problems continue, contact an HVAC expert. Also, if you notice discoloration when you check the pilot light, get professional help. If there are cold spots in your home, even though hot air is coming out of the air vents, the issue could be different from your furnace not working.

Why is my heat and AC not blowing in my house?

The most common problems that cause a lack of airflow include frozen coils, broken fan and restricted airflow due to dirty air filters or vent obstruction. However, there are many other issues that can lead to minimal airflow, so it may be necessary to ask the professionals.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

How do furnace and AC work together?

The air conditioner will sit outside the home cooling while the furnace works inside the home to heat with fans and coils. Both systems use your home's ductwork and vents to transport warm and cool air. Alternatively, a heat pump and an air handler might be paired together to form a complete system.

Will furnace work if AC is broken?

They share system components, like a blower, ducts, and vents. However, the furnace and AC are two distinct appliances that run independently. Because of this, it's unlikely that your furnace and air conditioner will break down at the same time.

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