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Mini-split not cooling, leaking, or showing an error

DIY troubleshooter · causes ranked by how often each turns out to be the problem, in our judgment (no dataset ranks them)

Ductless mini-splits fail in a few repeatable ways: dirty filters and coils, condensate that cannot drain, remote or mode settings, and error codes that name a sensor or a communication fault. The outdoor unit and refrigerant lines are pre-charged and off limits.

36-second explainer. Safe homeowner checks for a mini-split and where the licensed-pro line is.Stock footage via Pexels. Music: “Broken Windshield” by K4MMERER (Jamendo, CC BY-SA). All credits.
Wall-mounted ductless mini-split indoor unit in a modern room, the head whose filters and drain line you check
Stock photo, not our work. Photo by NEOSiAM 18+ via Pexels.

At a glance

Likely causes
6ranked, most likely first
Safe to check yourself
4free checks
Needs a technician
21 with a hard-line hazard
Pro diagnostic visit
$190median, 62 reports

Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.

Where this happens in your system

Mini-split not cooling, leaking, or showing an error: the parts this page is about
Mini-split not cooling, leaking, or showing an error: the parts this page is aboutA cross-section of a house. Indoors: a wall thermostat, an indoor unit in a closet with an air filter, blower and evaporator coil, supply ducts in the attic with ceiling vents, a condensate drain line that exits through the wall, and a breaker panel. Outdoors: the condenser unit on a pad, joined to the indoor unit by two refrigerant lines and fed through a disconnect box. Highlighted on this page: Air filter; Condensate drain line, pan and float switch; Outdoor unit: compressor, fan and condenser coil; Refrigerant lines.
  1. ThermostatThe wall control. It tells the system when to run.
  2. Air filter on this pageCatches dust before the air reaches the blower and coil.
  3. Indoor unit: blower and evaporator coilThe blower moves the air; the cold coil cools it.
  4. Ducts and ventsCarry cooled air to the rooms and bring return air back.
  5. Condensate drain line, pan and float switch on this pageCarries off the water the coil pulls out of the air.
  6. Outdoor unit: compressor, fan and condenser coil on this pageMoves the heat from your house to the outdoors.
  7. Breaker panel and outdoor disconnectThe power feed to the system, and its local shut-off.
  8. Refrigerant lines on this pageTwo copper lines that link the indoor coil to the outdoor unit.

Simplified drawing, not to scale. Real systems vary: the indoor unit can sit in an attic or closet, the ducts can run in the attic or under the floor. A mini-split has no ducts or air handler: a wall-mounted indoor unit joins the outdoor unit by refrigerant lines. The filter, drain and outdoor-unit checks are the same idea. Original illustration, not a photo.

Likely causes, most likely first

Stock photo, not our work. Photo by Alex Domínguez via Pexels.

  1. Close-up of a dark metal mesh with a hexagonal pattern, a stand-in for the mesh of an air filter
    Stock photo, not our work. Sergei Starostin via Pexels.
    1

    Dirty indoor filters

    You, safely2Part on the diagram

    How to checkOpen the front panel of the indoor head. Mesh filters coated with dust reduce airflow and cause weak cooling or icing.

    Typical repair costFree to check.

  2. Air conditioner remote with temperature set at 28°C on a yellow background
    Stock photo, not our work. Andrey Matveev via Pexels.
    2

    Remote or mode set wrong

    You, safely1Part on the diagram

    How to checkRead the remote display: Dry, Fan, or Heat modes do not cool. Dead remote batteries mean the head never gets a command. A set point above the room temperature stops the cooling.

    Typical repair costFree to check.

  3. Close-up of industrial pipes forming a pattern on a building's exterior wall, shot outdoors
    Stock photo, not our work. Sonny Sixteen via Pexels.
    3

    Drain line kinked or clogged

    You, safely5Part on the diagram

    How to checkWater dripping from the bottom of the indoor head or running down the wall, or a gurgling sound. The drain hose is a small flexible tube that clogs with algae.

    Typical repair costFree to check.

  4. External air conditioner unit placed on metal platform near gray shabby wall of modern building on street
    Stock photo, not our work. ready made via Pexels.
    4

    Blocked outdoor unit

    You, safely6Part on the diagram

    How to checkVegetation, snow, or debris around or on top of the outdoor unit.

    Typical repair costFree to check.

  5. Participants learn AC repair during a hands-on session in Delhi, India
    Stock photo, not our work. Multitech Institute via Pexels.
    5

    Error code from a sensor or communication fault

    Licensed pro3Part on the diagram6Part on the diagram

    How to checkA blinking light pattern on the indoor head or a code such as E1 or F1 on the display. Codes differ by brand; match it against your model's manual.

    Typical repair costNo repair price stat for this cause. A diagnostic visit runs: Median $190 (most $100–$290), 62 homeowner reports.

  6. Detailed close-up of a hand holding a pressure gauge, ideal for mechanical themes
    Stock photo, not our work. Tima Miroshnichenko via Pexels.
    6

    Refrigerant leak at a line set or flare joint

    Certified pro only (hazard)8Part on the diagram

    How to checkOily residue at the flare connections, the pipes iced over, or the unit blowing weakly cool. A DIY-kit install that skipped a leak test is a common source.

    Typical repair costRefrigerant leak repair: Median $1,320 (most $800–$3,000), 32 homeowner reports; Refrigerant recharge: Median $690 (most $460–$1,200), 48 homeowner reports

Ranks are editorial, not measured. A price is what homeowners reported for that one part or job, not a quote for the cause on that row, and a cause can involve more than one part. The reports do not separate mini-splits from central systems, so treat these prices as a rough guide for ductless. Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.

$190

Median pro diagnostic visit, from 62 homeowner reports

Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.

Safe to do yourself

These checks need no tools beyond a screwdriver, a hose, or a vacuum. Do them in this order.

  1. 1. Dirty indoor filters

    Free to check
    1. Turn the unit off with the remote and switch off its wall switch or breaker.
    2. Lift the front panel and slide out the mesh filters.
    3. Rinse them in lukewarm water with mild dish soap and let them dry fully.
    4. Reinstall and run the fan for a few minutes before cooling.

    2 Air filter

  2. 2. Remote or mode set wrong

    Free to check
    1. Replace the remote batteries.
    2. Select Cool, set the temperature 5 degrees below the room reading, and point the remote at the indoor head.

    1 Thermostat

  3. 3. Drain line kinked or clogged

    Free to check
    1. Turn the unit off and confirm the drain hose runs downhill with no kinks.
    2. Check where the hose exits outside for a blockage, such as insects or dirt.
    3. If the tray is full, let it drain before restarting. A blocked hose inside the wall needs a pro.

    5 Condensate drain line, pan and float switch

  4. 4. Blocked outdoor unit

    Free to check
    1. Turn off the breaker for the unit.
    2. Clear plants and debris, keeping at least the clearance listed in the manual.
    3. Restore power.

    6 Outdoor unit: compressor, fan and condenser coil

The hard line: stop here and call a pro

The causes below are not DIY, and we give no repair steps for them. Each carries a specific danger.

Source: Stationary Refrigeration and Air Conditioning (Clean Air Act Section 608), 2026-09-30; retrieved 2026-09-30.

Needs a technician, but not a hard-line hazard

5. Error code from a sensor or communication fault

Codes involving the compressor, overcurrent, or the outdoor board sit behind the outdoor unit's electrical panel, which holds line voltage and capacitors. Homeowner work stops at reading the code and resetting power once.

Participants learn AC repair during a hands-on session in Delhi, India
Stock photo, not our work. Photo by Multitech Institute via Pexels.

Local: Tampa Bay outer ring

Stock photo, not our work. Photo by ready made via Pexels.

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Counts: businesses with an active license and a city address in the Tampa Bay outer ring, from FL DBPR construction licensee extract (CONSTRUCTIONLICENSE_1.csv), retrieved 2026-10-05. A license says the state permits the work, not that the work is good.

What this repair costs here

A pro visit starts with a diagnostic fee. Homeowners reported: Median $190 (most $100–$290), 62 homeowner reports. The repairs behind the causes on this page:

Mini-split not cooling, leaking, or showing an error: repair prices homeowners reported
  1. Refrigerant leak repair N = 32
    $1,320 $800–$3,000
    Refrigerant leak repair: median $1,320, middle half $800 to $3,000, 32 reports
  2. Refrigerant recharge N = 48
    $690 $460–$1,200
    Refrigerant recharge: median $690, middle half $460 to $1,200, 48 reports

Reported price, U.S. dollars

Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.

Show the repair prices as a table
Mini-split not cooling, leaking, or showing an error: repair prices homeowners reported
RepairMedianMost (middle half)Reports
Refrigerant leak repair$1,320$800–$3,00032
Refrigerant recharge$690$460–$1,20048

These are national prices. We do not have enough Tampa Bay outer ring reports to publish a local one.

If the repair ends in a full replacement, the closest local cut is Florida: a median of $12,000 (most $9,400–$15,600) across 55 full-system reports, against $13,650 across 588 reports nationwide. See the AC repair cost guide and the AC replacement cost guide for every repair and job we have enough reports to price.

Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.

Utility rebates

A pro fix for this symptom can end in a replacement. If it does, these Tampa Bay outer ring utility programs pay for qualifying equipment. Confirm your utility and eligibility first.

Residential HVAC rebates from utilities serving the Tampa Bay outer ring, checked 2026-09-30
ProgramUtilityAmount
Home Energy Improvement: AC replacementDuke Energy Florida$300
Home Energy Improvement: heat pump upgradeDuke Energy Florida$500
Home Energy Improvement: strip-heat replacement (high efficiency)Duke Energy Florida$600
Home Energy Improvement: strip-heat replacement (higher efficiency)Duke Energy Florida$1,000
Energy Efficient Heat Pump RebateLakeland Electric$450 (mini split $225 per condensing unit)
HVAC Annual Maintenance RebateLakeland ElectricUp to $100 per year (the cost of the inspection)
Heating & Cooling Program: standard tierTampa Electric$40 for SEER 16.0 / SEER2 15.2
Heating & Cooling Program: high-efficiency tierTampa Electric$550 for SEER 17.0 / SEER2 16.2

Frequently asked questions

Stock photo, not our work. Photo by Anh-Bao Tran-Le via Pexels.

Why is my mini-split not cooling?

Set the unit to Cool with a temperature several degrees below the room temperature, then clean the indoor filters and clear debris from the outdoor unit. Trane says to trim shrubs back so they stay two feet from the outdoor unit.

Write down any error code for your technician. A refrigerant leak is one cause, and Trane says only a trained HVAC technician can find the leak, repair it, and recharge the system.

Checked against: Trane: Why Is My Mini-Split Not Cooling?. Pages opened 2026-09-30.

How do I clean a mini-split filter?

Turn the unit off at the remote or breaker, lift the front panel, and slide the filters out. Rinse them under lukewarm water from a faucet spray, and use a mild, non-abrasive detergent only if they are greasy. Let them dry completely, because a wet filter can promote mold growth.

Slide them back in and close the panel. Trane says to clean them as often as every two weeks in peak season and once a month otherwise. Carrier says every 4 to 6 weeks.

Follow your owner's manual.

Checked against: Carrier: What is a Mini Split Air Filter? Complete Guide & Maintenance; Trane: Do Mini-Splits Have Filters?. Pages opened 2026-09-30.

Can I install a mini-split myself?

No, not without Section 608 certification. EPA's Q&A on R-410A units says adding or removing refrigerant from a mini-split as part of installation, or connecting or disconnecting hoses or pre-charged lines, requires Section 608 technician certification. That includes pre-charged line sets.

Trane lists improper installation as a cause of mini-split refrigerant leaks. Use a certified installer.

Checked against: Trane: How to Identify and Fix Mini-Split Refrigerant Issues; U.S. EPA: EPA's Refrigerant Management Program: Questions and Answers for Section 608 Certified Technicians. Pages opened 2026-09-30.