Why does my brand new AC not cool as well as the old one?
New cooling systems often feel less effective because installers may misconfigure airflow settings or fail to balance multi-room temperatures properly. This leaves homeowners dealing with rooms that stay significantly warmer than they were with older equipment, causing regret and doubt over the replacement choice.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Using blackout curtains
- 2Contacting the installer to adjust the fan speed and refrigerant charge
- 3Buying ecobee sensors and a digital thermostat to check for equipment discrepancies
- 4Dropping the desired temperature setting to force the units to run harder
- 5Digging through thermostat logs and researching fault codes independently
- 6Flipping the air filter direction
- 7Checking breakers and outside unit components
- 8installing full-house dehumidifiers
- 9hiring multiple HVAC companies
- 10adding portable dehumidifiers
- 11getting an energy audit
- 12using a temporary window unit
- 13Replaced the reversing valve
- 14Replaced the liquid line filter drier
- 15Disconnecting the reversing valve from the motherboard
- 16Sealing gaps and cracks in the door and floor
- 17Switching from a single-hose to a dual-hose portable unit or a window unit
- 18Waiting for the installation technicians to return and finish servicing the system
- 19cover skylights with tarps
- 20installing window tint
- 21installing ceiling fans
- 22adding more AC units
- 23having a technician check the exact model numbers
- 24inspecting the electrical breaker
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“So I have two mini split units, senville brand both 12,000 btu. It’s 95 degrees right now and my house is 85 degrees upstairs and 80 degrees downstairs. I genuinely don’t know what to do.”source ↗
“For context-I live in Houston area, so it’s hot and very humid 6+ months out of the year. So; back in April my AC was set at 70 degrees but wouldn’t get below 78/80 degrees all hours of the day and humidity in our house was reaching almost 70%.”source ↗
“At this point we’ve spent upwards of $9K on our AC system and it is set at 70 degrees and can’t get below 75 degrees—>even overnight when it’s 77 degrees OUTSIDE. And our humidity is still high as well….completely at a loss of what else it could be and just looking for suggestions on what to do”source ↗
“I got 2 new Carrier Infinity units last week and so far I've been underwhelmed.”source ↗
“We also now have a room that is significantly warmer upstairs than before.”source ↗
“I noticed now, approx 4 hours later, that it’s blowing about 65 at that same vent and it’s 76 in here.”source ↗
“after spending so much $ I have some anxiety about it.”source ↗
“the next day my wife said she felt the new system didn’t cool as well as our 15 year old carrier did.”source ↗
“So I’m left now trying to figure out what’s going on and hoping we didn’t make a mistake going with the installer and unit we went with.”source ↗
“Reaching desired temp for the house. Which our old units could do. One room warmer than it was on the old units.”source ↗
“its not blowing cool air.”source ↗
“The installer is stumped, the company i bought it from is refusing to offer any help”source ↗
“Im at my wits end here. Ive been struggling with these companies since August 11th.”source ↗
“for whatever reason it doesn’t seem to be doing a good job at keeping my little shed cold.”source ↗
“After being on for about a half hour, the room read 77 while the air coming from the unit measured 66.”source ↗
“There is a very small leak coming from my door too which i do plan to seal up but could that make a major difference?”source ↗
“That 18-19F split just tells you it’s cooling right now. It doesn’t really prove the setup is correct.”source ↗
“The R22 only - label on a 1996 coil paired with an R410A condenser would definitely make me question what was actually done back then.”source ↗
“And yeah, if the condenser says 40A max and it’s actually on a 50A breaker, I’d get that looked at too.”source ↗
Where this came up
People with this problem also raised
- 10Refrigerator and freezer stopped cooling completely with loud humming noise
- 3Refrigerator stops cooling properly after being moved on its side
- 3Thermostat doesn't work after opening it up
- 9Why is one bedroom getting way more air than other rooms?
- 2Mini-split can't keep house warm when it freezes outside
- 2Why is my house so hot after getting a new roof?