Should I replace my furnace if I replace my air conditioner?

In many cases, your original air conditioner and gas furnace were installed as a matched set.  When one needs to be replaced it doesn’t necessarily mean you have to replace both, but it’s a good time to start thinking about your options.   You might consider upgrading to a heat pump system or a dual fuel system which can reduce energy costs during the spring and fall heating seasons. If you call a contractor to come out and evaluate your options for repair or replacement it’s a good time to ask about long-term solutions in addition to the quick fix.  A qualified contractor should be able to tell you about the usable life remaining in your system and provide you with several recommendations for short, mid and long-term solutions based on your needs and preferences. It’s also a good idea to ask about scheduled maintenance solutions which can help keep your system running longer and in better condition.

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23 thoughts on “Should I replace my furnace if I replace my air conditioner?

  1. My air conditioner on my roof clearly needs replaced. The furnace is about ten years old. Should it be replaced as well?

    • If it’s a gas furnace it probably has another 5-8 years of life left so long as it’s been well maintained. The important thing is to have it inspected by your contractor and have them check for cracks or signs of excessive wear. If the inspection shows it to be in good shape, you are probably ok to just replace the AC and leave the furnace. If, however the inspection shows excessive wear then you will want to consider replacing it as well.

  2. My oil furnace is 16 -17 years old. I would like to add AC to my house but the furnace is too tall. My options are to go to gas and AC which is 10,000 or to put mitshubishi a/cs in for around 8. Would I be smarter to replace the whole furnace since it is already 16 years old?

    • Hi Sue – your decision might depend on where you live and the temperature and humidity variations you will experience throughout the year. On average, HVAC systems in the US typically last about 14-16 years before they are replaced but that number can vary based on run time – i.e. your furnace might last longer in the south but the life would be shorter in the north. We always recommend talking to few different contractors, not only to make sure you are getting a fair price but to also make sure you find a contractor who can help answer your questions and do a good job on the sizing and installation. There are a few other articles and posts on this site that get into the details of ductless versus central ducted systems so you might want to use the search tool to review that information.

  3. We have a Borg Warner Furnace a/c unit. A couple of days ago, we smelled something like something was cooking. The unit blower went out. Would it be better to replace or repair? The model # P3UGB10N04001A. and mentions something about 40,000 BTU. I was researching for a unit but not sure on 1.5, 2 or 2.5 ton. unit.

    • Hello Angela,

      I suggest getting a few quotes from contractors before deciding on whether to replace or repair your unit. You can visit ACCA locator (link below) to get a list of professional contractors in your area:

    • Hi George. You might be referring to the GLUA75 instead of GKUA75 Heat Controller Gas Furnace model.
      Based from our wild card search, the following links may help with the dimensions that you’re looking for:

  4. Shelly, You wouldn’t need to replace the furnace twice if you left the existing AC in place but if you did that you’ll likely need to replace the AC in a few years anyway. Typically we see AC’s last anywhere from 10-18 years. The difference is usually based on where you live and how often you’ve run your system. If you’re in Florida, getting 10 years out of an AC is about all you should expect. If you’re in Idaho on the other hand, getting 17 years out of your AC is not unusual. It’s usually much cheaper to buy a furnace w/ an AC than to get them separately at different times because they’re at your house anyway. If you live in the east or southeast especially, getting a new AC w/ a new furnace probably makes sense. However if you’re in a dryer/cooler climate (such as the west), it might make sense to hold off on the new AC. Anywhere in between such as the Midwest, and it could go either way. Ultimately getting multiple bids and second opinions is going to be your best bet.

    • Shelly – depending on where you live you might also have them quote a heat pump or a dual fuel system which is a heat pump with a gas furnace to use in the coldest part of the season. I would also look into a system with a SEER rating of 16 or higher that has at least two steps/stage of capacity modulation to allow better energy savings and comfort benefits on humid days and nights.

  5. My 30+ year old furnace is shot and has to be replaced. I have been told that I need to replace my 11 year old working air unit at the same time, because it takes R2 fuelent & when it does go out I will have to replace it and the furnace. I don’t want to have to replace the furnace twice, but I also don’t want to get both if that’s not the case.

  6. Hi Julie – those sound like fairly standard parts so your contractor should be able to replace them. On the other hand, our research shows that most HVAC systems are replaced after about 16 years more or less depending on the geographic location and the run time, etc you might be ready for a new system. Your contractor should be able to advise you on whether to repair or replace your furnace. You might also ask about adding a high efficiency air conditioning while you are at it and maybe consider a heat pump or dual fuel system depending on your climate. We usually recommend getting 2-3 quotes from different contractors before deciding. I hope this answers some of your questions.

  7. I have a Borg Warner/York Division furnace ’78, installed in ’79. Never had any major repair problems, but now it’s making a clanking noise, like something is loose, but it continues to provide heat….I called the Hvac guy and he told me my blower bearings and shaft are shot.
    My question is, are these parts basic or universal for furnaces and can it be repaired? Is my unit too old to repair?
    The model # is UG140BN-1B and the serial # is B0-135121.

  8. I had a friend repair water leak on roof around furnace exhaust chimney flashing. While removing damaged plaster in dining room caused by the rain water traveling down on outside of the double exhaust pipe, I noticed that when the heater was on and the pipe heated up, that moisture appeared to show itself on the pipe. I went to inspect the roof flashing and notice that at the very top of the two pipes the opening where to two pipes end had been sealed. My thought is that it should not be sealed to allow condensation between the two pipes to escape. Is that correct?

  9. Had a friend repair roof leak surrounding furnace exhaust flashing. Rain water was coming in around flashing and going down outside of double piping and causing water damage on interior wall in dining room. While removing old plaster(it’s an old house!) I noticed slight moisture dripping on outside of exhaust pipe that only showed itself when the furnace was on and the pipe heated up. I inspected the top of chimney on roof and noticed that a seal of heat resistant chalking had closed the air gap between the outer and inner pipe at the very top. It’s my guess that condensation is now trapped between the two pipes. Should I open the seal at the top of the pipes to allow for condensation to escape??

    • Jenny, Our policies for this site do not allow us to comment on or recommend particular OEM brands of equipment. However, we do try to recommend the best “types” of equipment for various homes and geographic locations. It is difficult to tell much about your application from your post so you might want to read some of our articles on this topic, like
      and there are others with related material and the site is seachable. In general, I can tell you that there has been a recent trend toward using a high effy (16 SEER and up) heat pump in combination with a traditional gas furnace (called “dual fuel”) to give you the best comfort plus higher efficiency heating and air conditioning. The option to use the gas furnace in the coldest conditions or when gas prices are low relative to electricity is also an attractive option depending on your utility rates and seasonal heating and cooling needs in your area. Hope this helps.

  10. I have another house so I can’t look at the furnace my paper work has three model numbers plus serial numbers TTR036C100A /ser; H38269286; TUE100A948B/ser J39540371; TXC037C4HPB Ser K04754729
    my equipment was installed 03-22-1995 the heat was working and then it started blowing cold air it tryies to start and then it goes out I had a man look at it He said trane updated the way it works and I have to change something out He was going to call trane Monday and see what it will cost does this sound right

    my furnace blows cold air or it shuts down right after it starts up it was in stall in 1995 I have three models numbers on my paper TTR036C100A:TUE100A948B;TXC037c4HPB Ihad a man look at it and he said something was out dated and it has to be replace some senory switch that trane had a kit to upgrade it can you tell me if this is true I never had any trouble with furance befor now

    • What he suggested is possible but you can do an internet search on those model numbers to learn more. Having your contractor talk ng with the OEM is a good idea too. If you are not comfortable with one assessment you can also get another opinion from another contractor but it looks like you are on the right path to getting it fixed as the OEM should know.

  11. Deluxe Digital Non-Programmable Thermostat
    From Home Depot.
    Wondering if this works with a Coleman Furnace Model G8C12520MUD11A

  12. Hi Charlotte,

    The best course of action would be to contact a local HVAC contractor in your area. Trailer furnace replacement can be a specialty type of system, so talk to the contractor up front and let him know the situation. The contractor can then select the best possible replacement system on your needs and location.

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