The short answer
Defrost mode is normal. On a cold, damp day the outdoor coil frosts over, so every so often a mini split stops heating to melt it off. The head stops blowing warm air, the outdoor fan stops, and you may hear a whoosh and see steam and water coming off the outdoor unit. It lasts a few minutes, up to about 15, then the heat comes back. In Northern Virginia it happens most on days in the 30s with drizzle or fog. It’s a problem when it never ends, when ice keeps building between cycles, or when the head blows cold for half an hour.
What defrost looks and sounds like
- The head stops blowing, or barely blows. It holds its fan so it doesn’t blow cold air at you.
- A light blinks or a code shows on some heads. Fujitsu’s OPERATION lamp blinks slowly. LG has a defrost indicator. Samsung, Pioneer and MrCool show dF. Gree shows H1.
- Outside, the fan stops while the compressor keeps running.
- A whoosh or a hiss when it starts and ends. That’s the valve switching the refrigerant’s direction.
- Steam and water coming off the outdoor coil.
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How long it lasts, by brand
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| Brand | What the manual says |
|---|---|
| Daikin | Heat stops for about 4 to 12 minutes, with a flowing sound. Water or steam from the outdoor unit. |
| Fujitsu | Up to 15 minutes. An indicator blinks. Steam, water and a sizzling sound are normal. |
| LG | Defrost ends at 12 minutes, or sooner once the outdoor coil reaches 50°F. Both fans stop. |
| Mitsubishi Electric | When it starts up in the middle of a defrost, warm air can take up to 10 minutes. A water flowing sound is normal. |
Right after defrost, and every time you start it in heat mode, the head may wait a few minutes before it blows. That’s cold air prevention, and it’s normal too. Mini split not heating covers the rest of the reasons a head blows cool.
Why it happens
In heat mode the outdoor coil runs colder than the air around it, so it can pull heat out of winter air. When that air is near freezing and damp, its moisture freezes on the coil. Frost blocks the airflow, so the system runs in reverse for a few minutes to melt it off.
A raw day in the 30s with drizzle frosts a coil faster than a dry, colder night. That’s why defrost seems to come and go with the weather, not just the temperature.
Normal or a problem
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| What you see | Normal? | What to do |
|---|---|---|
| The head stops blowing for a few minutes, then the heat comes back | Yes | Nothing |
| Steam and water off the outdoor unit | Yes | Make sure the water drains away from the unit |
| A whoosh or a hiss at the start and end | Yes | Nothing |
| Defrost again and again on a cold, damp day | Yes, if the coil clears each time | Nothing |
| Ice building between cycles until the coil is a solid block | No | Turn it off and read heat pump frozen, then call |
| Defrost running well past 15 minutes, or never ending | No | Call. Often a sensor or the valve |
| The head blows cold for half an hour or more | No | Check the mode and the filters, then call |
| Ice on top of the unit under a dripping gutter | No | Fix the gutter. Defrost can’t melt what lands on top |
Help it defrost
- Keep the outdoor unit up off the ground on a pad, risers or a wall bracket, so the melt water has somewhere to go. That’s why ours sit up high.
- Clear snow off and around it after a storm, gently, by hand or with a broom.
- Fix a gutter that drips onto it. Water landing on the unit freezes on top, where defrost can’t reach.
- Don’t chip ice off with anything hard, and never use a heat gun or a torch. The fins and coil puncture easily, and that’s a refrigerant leak.
- Don’t switch it off during defrost. It ends on its own, and a restart just delays the heat.
Where the water goes
The melt runs out the bottom of the outdoor unit. On a freezing night it can refreeze under the unit and build a little mound of ice. A unit up on risers clears it. One sitting low can end up frozen to its pad, and that’s when the fan starts scraping ice. Heat pump covered in ice and heat pump frozen cover what to do, and they apply to a mini split’s outdoor unit too.
Codes that look like defrost but aren’t
H1 on a Gree is defrost, but H1 on a Pioneer is a high pressure fault. Check the brand before the code. 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.
For a ducted heat pump, heat pumps in a Virginia winter explains defrost and backup heat, and mini split making noise covers the other sounds a mini split makes.
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 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
How long does a mini split defrost cycle last?
A few minutes, up to about 15. Daikin says about 4 to 12 minutes, LG ends defrost at 12 minutes, and Fujitsu says up to 15.
Why does my mini split stop blowing air in heat mode?
Usually defrost. The head holds its fan so it doesn’t blow cold air while the outdoor coil melts its frost. The heat comes back within about 15 minutes.
Is steam coming off my mini split outdoor unit normal?
Yes, during defrost. The coil melts its frost and some of it comes off as steam.
How do I know if my mini split is stuck in defrost?
Defrost that runs well past 15 minutes, comes back with ice still on the coil, or leaves the head blowing cold for half an hour. Turn it off and call.
Should I chip the ice off my mini split?
No. The fins and coil puncture easily. Clear loose snow by hand, fix anything dripping on it, and call if a solid block of ice keeps coming back.
