Why is my mini-split running but not cooling?
The usual causes are a clogged filter or coil, low refrigerant from a leak, an iced-up indoor coil, a fault in the outdoor unit, or simply the wrong mode or set point. Filters and settings you can fix yourself; the rest needs a technician with gauges and the right diagnostic tools for ductless systems.
Mitsubishi Electric's own operation manual puts it plainly: when the air conditioner does not cool or heat, there is a possibility of refrigerant leakage — and that's a job for a technician, not a top-up can. If you're in Florida and want someone who works on these units, start with our Florida mini-split repair line once you've done the checks below.
What should I check before calling?
- Mode and set point. "Dry", "Fan" and "Auto" modes don't cool the way "Cool" does. Set it to Cool, a few degrees below room temperature.
- Filters. Open the front panel and look. Daikin and Mitsubishi both recommend cleaning the filters about every two weeks; a matted filter can cut airflow badly.
- Give it a few minutes. Many units deliberately hold the compressor off after a restart — Daikin's manual says to wait 3 to 4 minutes, and Fujitsu notes a 3-minute protection delay after a power interruption.
- Power and remote. Check the breaker and the outdoor disconnect, and swap the remote batteries — Fujitsu's own checklist covers power, breaker, timer, filter, blocked grilles and remote batteries.
- The outdoor unit. Is its fan spinning? Is it boxed in by plants, a fence or storm debris? If it's silent while the indoor unit runs, see outdoor unit problems.
Why does my mini-split blow cool air in heat mode?
On a cold morning, a heat pump has to defrost its outdoor coil now and then. Fujitsu explains that during automatic defrosting the unit stops for 7 to 15 minutes and the operation lamp flashes — that's normal. If it never warms up, only blows cool air, or shows a code, the reversing valve, a sensor or the refrigerant charge may be the problem. Note any code and see error codes & blinking lights.
Is ice on my mini-split a problem?
Ice on the indoor coil or the copper lines in cooling mode means air isn't moving across the coil (dirty filter or coil, failing blower) or refrigerant is low. Switch the unit off and let it thaw — running it frozen can push water out of the indoor unit and strain the compressor. If it ices again after a filter cleaning, it needs a technician; a refrigerant leak is a common cause.
What will the technician do?
Expect them to check airflow and the coil, measure temperatures and pressures, read any stored fault codes, and test the outdoor fan and compressor. If refrigerant is low, a proper repair means finding the leak first — usually at a flare joint — not just adding more. Ask for the diagnostic fee up front and a written estimate before the repair.
When is it time to repair vs. replace?
A failed compressor on an older system, an obsolete refrigerant, or repeated leaks can tip the balance toward replacement. See repair or replace for the factors to weigh.