The short answer
A mini split in Northern Virginia that won’t cool is most often set wrong, choked by dirty filters, or held back by a dirty or blocked outdoor unit. Check that it’s in Cool, the set temperature is lower than the room, the remote has batteries, the filters are clean and the outdoor unit is running and clear. Then give it 3 minutes; most heads wait that long after a restart. If it still blows warm, or there’s ice on the lines, it’s usually a refrigerant leak, a fan motor or a sensor. Those need a tech.
Check these first
- The mode: Cool, not Fan, Dry, Heat or Auto. On a multi zone system every head has to be in the same mode, because one outdoor unit can’t cool and heat at once.
- The set temperature: a few degrees lower than the room, to test it.
- The remote: fresh batteries, and its display matches the head.
- The filters behind the front panel. Clogged filters choke the airflow and can freeze the coil.
- The outdoor unit: is it running? Is it buried in leaves, boxed in by shrubs or caked in dirt like the coil in our photo?
- The breaker or the disconnect box for the outdoor unit.
- Three minutes after any restart. Daikin, Mitsubishi Electric and LG all hold the compressor off that long to protect it.
Free Furnace With a New AC
Put in a new AC with its matching coil and a basic single-stage gas furnace goes in with it, installed together. See the free furnace
Want your own number before anyone comes out? The HVAC estimator prices your house in a few questions.
Things that look broken but aren’t
- Dry mode runs the fan low and stops and starts on its own. Mitsubishi Electric and Fujitsu both say so. It’s pulling moisture out, not cooling hard.
- An inverter mini split slows way down as the room gets close to the set temperature. Quiet, gentle air near the target is it working right.
- A little mist from the louvers on a humid day is normal, per Mitsubishi Electric.
Symptoms and causes
Swipe to see all columns →
Swipe to see all columns →
| What you see | Usually why | What to do |
|---|---|---|
| Air blows, but not cold | The wrong mode, dirty filters or a dirty outdoor coil | The checks first. Rinse the outdoor coil gently with the power off |
| Weak airflow from the head | Dirty filters, or a dirty barrel fan | Clean the filters. The fan needs a tech: how to clean a mini split |
| Ice on the copper lines or the coil | Low refrigerant from a leak, or no airflow | Run it on fan only to melt it and clean the filters. If it comes back, call: mini split refrigerant leak |
| The outdoor unit isn’t running | The breaker, a board or a communication fault | Check the breaker, then call |
| The outdoor fan isn’t spinning while the compressor hums | The fan motor | Turn it off and call before it overheats |
| Cools most days, falls behind on the hottest afternoons | Sun on the room, sizing, or a dirty coil | The next section |
| One head cools and another doesn’t on a multi zone | A mode conflict, or that head’s sensor or fan | Check every head’s mode, then call |
| Water dripping from the head | A clogged drain or pump | Mini split leaking water |
The hottest days
Mini splits are built to cool in serious heat: Mitsubishi Electric and Daikin list cooling to 115°F outside on common models, and LG to 109°F. Fujitsu says a unit may stop to protect itself outside its range. What usually holds one back on a 98°F afternoon is a west facing room in full sun, a head sized for a smaller space, a dirty outdoor coil, or a door left open. Daikin’s own manual says the outdoor temperature, the humidity and the number of people in the room can keep a head short of the set point. If one room never catches up, zoning or ductless for one room covers the fix.
Codes
A code points to the part. CH07 on an LG is a mode conflict between heads. Refrigerant, fan and communication codes each have their own numbers by brand. Brand by brand: Mitsubishi, Carrier, Daikin, Fujitsu, LG, Samsung and MrCool, Pioneer, Gree and Senville. Every code family we’ve written up is on our error codes and warning lights page. On a Daikin, the owner steps from its manuals are in Daikin mini split not cooling or heating.
One reset, not ten. Turn the head off with the remote, switch the breaker off for about 5 minutes, then turn it back on. If the same code comes back, write it down with the model number from the label and call. Resetting a fault over and over can hide what it was protecting.
If it’s heating season
If the head blows cold in heat mode, that’s a different list: mini split not heating, and for the pause with steam outside, mini split defrost mode.
Repair or replace
Most no cool calls are a part and one visit. If the system is old enough that a new one makes more sense, it’s $1,500 off a new system, ductless mini split included, and the estimator shows prices with it already taken off. For a ducted AC, our AC repair page covers the same ground, and mini split repair covers what else breaks.
Book it
A mini split visit starts with our $99 diagnostic, and you get the repair price in writing before anything is opened. Call (703) 997-9757 or book a visit online and tell us the brand and the code or what you’re seeing. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Mitsubishi Electric, Carrier, Daikin, Fujitsu, LG, Samsung, MrCool, Pioneer, Gree and Senville are trademarks of their owners.
Questions people ask
Why is my mini split running but not cooling?
Most often the mode, dirty filters, or a dirty or blocked outdoor unit. If those check out and it still blows warm, it’s usually refrigerant, a fan motor or a sensor.
Why is my mini split blowing warm air in cool mode?
Check that it’s in Cool, not Fan, Dry or Auto, and that every head on a multi zone system is in the same mode. A dirty outdoor coil or a low charge can do it too.
How long should a mini split take to start cooling?
A few minutes. Most wait about 3 minutes after a restart to protect the compressor, then the air cools within a few more.
Why does my mini split stop and start in dry mode?
That’s normal. Dry mode runs the fan low and cycles on and off to pull moisture out of the air.
Can a mini split keep up in 100 degree heat?
Most can. Common models are rated to cool with 109°F to 115°F outside. Sun on the room, sizing and a dirty coil are the usual reasons one falls behind.
