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Is your ac blowing cold air but house still hot? There could be quiet a good number of reasons for this problem. But when you have an ac that is blowing cold air but not cooling your home, it could be a sign that:
- You have open doors and windows
- Your house isn’t well Insulated
- You have an undersized air conditioner unit
- your ductwork is leaky
- You have failing condenser fan motor
- Your ac capacitor is dead
- You have a dirty air filter
In this article, we’ll look at the common issues that could prevent your ac from cooling your home even though its running. Let’s take a look.
Read also: Air Conditioner Not Blowing Cold Air but Running
Why is My AC Blowing Cold Air but House Still Hot?
1. Open Doors and Windows
Open doors and windows could be the reason your ac is not cooling your home adequately. When you’re running your ac, you expect your home to start cooling. But when your windows or entrance doors are open, your air conditioner will struggle to keep your home cool.
As your air conditioner blows cold air, warmer air from outside will be drawn into your home and will displace the cooler air coming out of your vents or ac unit. This process will go on as long as you have open doors and windows. And that’s definitely why you can’t feel your home getting cooler.
How do I fix this?
If your ac isn’t cooling because of open doors and windows, just close open windows and doors. You’ll also need to seal off any open gaps between doors and between windows to prevent too much outside air from getting in.
To seal gaps between the doors, you can use the door blocker. Having a closed inside environment should get your ac to cooling your home again.
2. Undersized AC System
An undersized ac system will not be able to cool your home enough. That’s why you can have an ac blowing cold air, but your home doesn’t get cooled.
When you have an air conditioner system smaller than what your room or house needs, it will work harder to keep your home cool. Many times, it will work continuously without taking breaks and this can result in hefty electricity bills. See required BTUs per square feet here.
Sometimes, installers may not have taken the time to do a proper calculation for the right size of an ac system your home needs. Sometimes they can just ignore and install any ac system. Here is a chart of BTUs needed per square meter.
When you have an undersized air conditioning system, the best solution is to get the right sized one. Even though this can’t be an option for many, there are a few things you can do to improve cooling in your home if you have an undersized ac system. But if nothing seems to help, then you’ll definitely need to replace your ac system with a much bigger one.
Things you can do to help if you have an undersized AC System
If your AC is too small for your home, try:
- Closing windows and doors.
- Blocking gaps between windows and doors
- Switching off appliances that are not in use and that produce heat like stoves and electronic appliances such as Plasma TVs.
- Insulating your home on areas that are not properly insulated.
3. Home Not Properly Insulated
A home that is not properly insulated could be the reason for your ac blowing cold air but your house still hot.
If your house isn’t properly insulated or whose insulation has deteriorated with age could easily absorb heat from the outside into your home and the other way round.
You need to look for cracks and gaps and seal them off.
4. Failing Fan Motor
A fan motor that is failing can be another reason why your ac is not cooling enough. When you have a failing motor, your ac can blow cold air for about an hour or so. when your fan motor heats up, it will stop spinning your fan and the compressor high limit switch will kick into action to stop pressure from rising.
When the fan motor cools again, your condenser unit will start running. Meanwhile all you’ll notice in your home, is that the ac will be blowing cold air, but your set temperature point will not be reached, and your home will still be hot.
Solution to a failing fan motor
A failing condenser fan motor is hard to detect because the problem is intermittent. One moment the motor can run quiet well and another, it will stop. You can try checking on the condenser unit after you have turned on your thermostat.
Check how the condenser fan is running and if the speed is consistent. If it stops spinning along the way, try touching the motor with caution. A failing fan motor will usually overheat to a point that it can burn your hand.
If you have a bad fan motor, its best to replace it with a working one.
5. Bad Capacitor
A bad compressor capacitor is by far the most common reason for your ac not cooling your home. When you have a dead capacitor, you can have your air conditioner blowing air at room temperature, which can feel as cold, but it will never go down to the set temperature.
If a compressor capacitor is defective, you can have both your indoor fan working and your condenser fan working but the compressor won’t be running. It can be tricky for you to figure out what’s really going.
How can I replace a failed compressor capacitor?
A failed ac compressor capacitor is easily replaceable. The following are the steps to take when you’re replacing your ac capacitor:
- Confirm that your ac outdoor unit has power access.
- If your outdoor unit fan is running, you need to check if your compressor is running too. Usually, you’ll have noise coming from the compressor besides noise from your fan.
- If the compressor is quiet or not working, its possible your capacitor is dead.
- Turn on your condenser by pulling out the disconnect and by tripping the circuit breaker.
- Use a screwdriver to remove part of your condenser unit cover, be sure to unscrew, the part with an electrical compartment.
- Take note of details on your capacitor and take a snap of the wiring so you have no problem connecting the new capacitor.
- Sometimes, you can tell if a capacitor is bad if its top has bubbled. But usually, a multimeter is more accurate to tell if a capacitor is dead. If you have none of these just go ahead and get a new capacitor. They are quite cheap, about $15.
- Remember to use the details for buying a new one to avoid compatibility issues.
- Wait for your capacitor to arrive (if you ordered one online) and fit it
- If the ac works, congratulations, you have just fixed your own ac system
Also read: Air Conditioner Outside Unit Fan Not Working [Solved
6. Your Air Filter is Dirty
Air filters can also prevent your air conditioning system from blowing enough cold Air. Filters control the quality of air that gets into your AC system and eventually into your home. If your filters are dirty, they will restrict the amount of airflow that’s drawn into your ac system. Because of that, you won’t have enough cold air coming out of your vents. Coupled with the outdoor summer temperatures, this could explain why your house remains feeling hot.
We hope that after reading this article, you’ve learnt how to deal with an ac blowing cold air but house still hot. Otherwise, we would advise you to call in your local HVAC experts to come and assess the whole problem. Thanks for reading.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.