Whitegoods Help article

Frost free freezers and automatic defrosting fridges

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Quick Answer

Frost-free fridge freezers work by circulating cold air using a fan and automatically defrosting the evaporator with a heating element on a timed cycle. The most common problem is the evaporator freezing over – usually after the door is left open too long – which stops cold air circulating and causes the unit to warm up. A full manual defrost (unplugging for at least 12 hours) resolves this if the underlying cause is user behaviour rather than a sensor or heater fault.

How Frost-Free Refrigeration Works

In a conventional fridge freezer, the evaporator (the plate or coil that gets cold) is exposed inside the food compartment. Frost builds up on it and must be defrosted manually. In a frost-free appliance, the evaporator is hidden behind a plastic panel at the back of the food compartment, and cold air is circulated around the cabinet using a fan motor. The system automatically defrosts the evaporator on a timed cycle without any manual intervention.

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The evaporator

Hidden behind the rear plastic panel inside the food compartment. Cold air passes over it and is then distributed around the cabinet by the fan. When working correctly, small beads of ice may be visible on the back plastic wall – this is normal. During a defrost cycle you may see water on the back wall instead.

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The defrost heater

A heating element is built into the evaporator assembly. On a timed cycle, this heater runs briefly to melt any frost that has accumulated. The resulting water drains down channels in the rear wall, through a drain hole, and out to the evaporator tray on top of the compressor. The compressor generates heat that evaporates this water into the air behind the unit.

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The control system

Sensors, a defrost timer, and a PCB control the cooling and defrost cycles. This additional complexity means frost-free appliances have more components that can potentially fail compared to a simple conventional fridge – though they remain generally reliable.

Common Problems

Evaporator Frozen Over

The most common problem with frost-free appliances is the evaporator freezing over entirely. When this happens, the fan cannot circulate cold air effectively and the food compartment warms up. This can happen for two reasons:

🚪 Door left open (user cause)
If the door is left open for an extended period in warm or humid conditions, excessive moisture enters the cabinet and the evaporator ices over rapidly. Because the evaporator is hidden behind the rear panel, the extent of the ice build-up is not visible. A complete manual defrost (unplugging for at least 12 hours with doors open) typically resolves this if it does not recur.
⚙️ Defrost system fault
If the defrost heater, defrost sensor, or timer fails, the evaporator will ice over progressively even with normal use. The fault will recur after a manual defrost. This requires an engineer to diagnose which component has failed – heater, sensor, or PCB.

Fan Ice Build-Up and Noise

In severe cases of evaporator icing, ice can form around the fan motor itself. Before the fan seizes completely, it will catch on the ice and produce a distinctive high-pitched noise or intermittent grinding sound. If the fan seizes, cold air circulation stops entirely. This symptom almost always indicates the defrost system is not clearing ice correctly – either from a one-off door-open event or a defrost component failure.

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Do not use a hair dryer to defrost inside a frost-free appliance

Modern frost-free appliances contain a thermal fuse that protects the defrost circuit. Direct application of a hair dryer can trigger or damage this fuse. The correct method is to unplug the appliance and allow it to defrost naturally with the doors open over at least 12 hours.

Preventing Problems

  • ✅
    Check the door seals regularly using the paper test. A seal that is not creating an airtight closure allows continuous warm air ingress that overloads the defrost system over time. See our guide on frosting up in a fridge or freezer.
  • ✅
    Do not leave the door open longer than necessary. Each time warm moist air enters the cabinet, the defrost system must clear it. In humid conditions a few minutes with the door fully open is enough to cause problems.
  • ✅
    Do not overload door shelves on American-style fridge freezers. Overloaded doors on large American-style models may not seal correctly even when closed. The large door storage capacity makes overfilling easy – keep items within the designed weight limit for each shelf.
  • ✅
    Stack food to allow air circulation. Frost-free appliances depend on fan-circulated air. Items packed too tightly against the back panel or stacked to obstruct airflow within the cabinet create warm spots and reduce efficiency. Read the instruction manual for stacking guidance for your specific model. Manuals can be downloaded via our appliance user manuals page.
  • ✅
    Check the drain channel is clear. The channel at the rear of the fridge compartment that directs defrost water out through the back can become blocked with food debris. A blocked drain causes water to collect at the base of the fridge rather than draining correctly. See our guide on water in the base of a fridge.

Frequently Asked Questions

How does a frost-free fridge freezer defrost itself?

A heating element built into the evaporator assembly runs on a timed cycle – typically once or twice a day – melting any frost that has accumulated on the evaporator. The resulting water drains down channels in the rear wall and exits through a drain hole at the back, running into a tray on top of the compressor where it evaporates. This cycle repeats automatically throughout the appliance’s service life.

Why is my frost-free fridge freezer not cooling properly?

The most common cause is the evaporator freezing over – which stops the fan from circulating cold air effectively. This can happen after the door is left open for an extended period, or if the automatic defrost system has developed a fault (failed heater, sensor, or PCB). Try unplugging the appliance and leaving doors open for at least 12 hours to defrost manually. If it works normally afterwards but the problem recurs, the defrost system needs investigation by an engineer.

What does a high-pitched noise from a frost-free fridge mean?

A high-pitched noise or intermittent grinding from inside the cabinet is usually the fan catching on ice that has built up around it. This indicates the evaporator is frozen over and the defrost system is not clearing it correctly. Unplug the appliance and defrost it manually. If the noise returns after defrosting, the defrost heater, sensor, or timer has likely failed and needs replacement.

Last reviewed: April 2026.

Discussion

117 Comments

Grouped into 95 comment threads.

Washerhelp 4 replies There should only be ice on the back wall occasionally Rod. When in a defrost cycle the ice melts and runs down the back wall as water.

There should only be ice on the back wall occasionally Rod. When in a defrost cycle the ice melts and runs down the back wall as water.

Reddy

Likely replying to Washerhelp

Hi Washerhelp,

I appreciate your expertise, and would like your opinion. I am purchasing a new fridge and was planning on buying the Compact Summit.

I noticed that this has a manual defrost on the freezer. What will this mean in terms of my maintenance of the freezer? I don’t go into the freezer that often (maybe 3 times a week), but I am scared of what “Manuel defrost” means. I have nice wood floors in the kitchen, am I going to have ice build up that I cannot get rid of sans huge amounts of towels and syphoning water into the sink? How often will I have to defrost the freezer?

I currently have a White Westinghouse Frost Free freezer that is almost 20 years old… What sort of differences should I expect?

Thanks,
Reddy

Washerhelp

Likely replying to Reddy

Hello Reddy: The link you give has a link to the actual manual of that product which has a section on manually defrosting where it describes the process in detail for you. How often you have to do it depends on how often you open the freezer up and how long you keep the door open as well as how humid it is but if you don’t go in too often it shouldn’t need doing too often. I’m not familiar with the Westinghouse but if it looks like an ordinary fridge freezer as opposed to a frost free one.

Richard

Likely replying to Washerhelp

Hi Washerhelp,

I have a Diplomat APM6318 built-in larder.
Do these small stand alone fridges usually have a defrost timer, heater etc?
It is a wet wall fridge and I’ve noticed that ice beads form and then melt quite often (every time the thermostat is on or off). I would have thought the fridge would auto-defrost every 6 hours or so, not every time the thermostat cycles, unless there is no extra defrost capability.

Thanks for your help!

Washerhelp

Likely replying to Richard

Hello Richard: Larders tend to have a defrost cycle, which raises the temperature inside the fridge using a heating element (believe it or not) to melt the ice beads on the back wall. This means food doesn’t last as long in a larder fridge as it would in a normal fridge.

The water should run down the back wall into a large v-shaped channel with a small hole at the apex where the water runs into the back of the appliance onto the evaporator tray (on top of the compressor).

Washerhelp 3 replies A similar question was asked by ernie when he said his made a noise like a jack hammer - I replied underneath. Hope it helps

A similar question was asked by ernie when he said his made a noise like a jack hammer – I replied underneath. Hope it helps

AMBAR

Likely replying to Washerhelp

Dear Washerhelp
Thanks for such an informative blog. I have gone through most of the problems discussed above.
My problem is a bit different. We are planning to replace our existing refrigerator (which is not frost free and accumulates frost in freezer compartment.) I am currently in a city where continued suppy of electricity is a problem. The power normally goes off one hour each thrice a day. On some hot days, or due to grid power failure the shut down could be prolonged may be 6 to 8 hours. Now the issue is, with a freezer having forsting mechanism, there is lot of ice inside the freezer compartment, which can keep the frozen food intact for a longer period. I was wondering what would happen if there is no ice in the freezer compartment (if I buy fros-free fridge), and power goes off. I presume it would certainly impact the food quality and might spoil it or render it unconsumable.
what do you recommend in this scenario, shall we go for frost free or for old frost type?
thanks in advance
AMBAR

Stephen UK

Likely replying to Washerhelp

Hi Washerhelp

Many thanks for making the effort to put all of this information up. I know you’ve answered this problem before, but I’ve got a slight variation to ask:

I have one of those fridge / freezers where the fridge is cooled by pumping in cold air from the freezer compartment. Sadly, every few months, the fridge bit seems to stop working – I’m guessing because the air conduit gets blocked by ice. We empty both compartments (bye-bye lovely food) and switch it off and leave the doors open for a few days, and then all is ok again (for a few months). In this instance I’m a bit fed up and don’t want to lose all my food again, and wondered if there’s likely to be any way I can get in there manually, remove the ice blockage myself, and get the unit back up and running before the food has had time to go off.

Also, do you have any other tips as to things we might be able to do / not do to stop this happening in future (fyi we’ve had engineers out, but they just recommend the defrost solution!)

Thanks again for your help,
Stephen

Stephen UK

Likely replying to Washerhelp

Hi Washerhelp

further to the above comment, I’ve noticed something that may help diagnose the problem (if indeed it’s in any way different to the problems already mentioned on this board): when the f/f malfunctions in this way, it also seems to misread the temperature of the fridge section. It’s currently reading 2-3 deg Celsius, but the temperature in the fridge compartment is very clearly not that low (more like 18 – it’s warmer in there than it is in the room!)

Stephen

Washerhelp 3 replies I would try a defrost Tony R. Jenny: Check your instruction book, hopefully they will mention these things. Frost free fridges can get hot at the sides and the fans do run on and off a lot but shouldn't run constantly once settled in.

I would try a defrost Tony R.

Jenny: Check your instruction book, hopefully they will mention these things. Frost free fridges can get hot at the sides and the fans do run on and off a lot but shouldn’t run constantly once settled in.

jean UK

Likely replying to Washerhelp

Washerhelp,
Just found your site. What a help I found it. My sanity is returing.
Situation: Am really rather ill. Have to store temperature controlled drugs injections in fridge 2 – 8 degrees. It’s a relatively new, expensive fridge/freezer. Jabs are useless if go out of temp. – it’s a nightmare. This stuff can cause cancer and lupus, etc.
Got a data logger. Seems the unit is suceptible to room temperature of kitchen vv cooking, food retrieval, overnight drop in the air temperature. I live in a bungalow. data logger shows teemp. in fridge drops to 1.5 during the night.

There must be millions of people who are storing vital drugs in domestic fridges and have no way of knowing that they have ‘gon out of temperature’. I have tried to engage the press media over here to address the situation as I feel the responsibility, loaded by the NHS, on folk who are already very ill is unacceptable. Sadly, they don’t recognise the importance. I have seen that the US authorities have seen the situation and are currently researching dedicated units – pity UK authorities are turning a blind eye.

I’m now going to buy a pharmacy fridge and hope that this will resolve the problem. I’m undecided whether to call an engineer to look at this Bosch fridge/feezer I have, or to cause it’s demise with a 15lb hammer! There must be a problem because the frequent fall of ice into the tray is sufficient to wake one up – from the other end of the house.

If you’ve read this … thanks for your patience. this morning I need to rant – I’ve been up since the crack of dawn.
Rgds Jean

Washerhelp

Likely replying to jean UK

Hello Jean UK: You are right in that you may need a pharmacy fridge. No domestic appliance manufacturer is going to guarantee their refrigeration is suitable for looking after such delicate medical products. Normal fridge temperatures should be between 0 degrees and 5 degrees so 1.5 degrees is perfectly OK for normal use.

The coldest part of a fridge is usually at the bottom, have you tried monitoring the temperature at the bottom of the fridge in case it remains colder? Also I would try setting the temperature as low as you can without getting lumps of ice in the milk, that could make a difference too.

jean UK

Likely replying to Washerhelp

Hello Washerhelp,
Sorry for the delay in answering. Been experimenting. Nope! Nothing works. Have now got a pharmacy fridge, all checked, set up and doing the business. I was abolutely amazed at the service/delivery … ordered it one day, here before 1pm the following day.

I can now sleep at night and stop asking questions which must seem daft to those in the trade. Thanks for taking the trouble to ‘hold my hand’ – I was glad of your input. Take care, and may all your problems be small and solvable.

GEORGE 2 replies Your article on 'how does it work' is very helpful but could you please explain the exact sequence of events from initial switch-on of a frostfree fridge freezer. e.g. what determines the temperature of the freezer section as I understand that the variable stat only controls the temperature in the fridge section. Maybe a little circuit diagram or would that be too much to ask. thank you

Your article on ‘how does it work’ is very helpful but could you please explain the exact sequence of events from initial switch-on of a frostfree fridge freezer. e.g. what determines the temperature of the freezer section as I understand that the variable stat only controls the temperature in the fridge section. Maybe a little circuit diagram or would that be too much to ask. thank you

Washerhelp

Likely replying to GEORGE

Hello George. Thanks, any decent frost-free fridge freezer should have a separate sensor for fridge and freezer. But as my article Freezer defrosted: Can you put a fridge freezer in a garage? describes some (presumably budget brands) only have one sensor or thermostat in the fridge section which causes problems if the unit is placed in a colder than a normal kitchen environment.

GEORGE

Likely replying to Washerhelp

Thanks washerhelp, I had thought that there would have been a second (hidden) thermostat controlling the freezer section. I guess I have the economy version, from Comet. Very hard frost coupled with a heating problem may have been the cause of my problem as the offending article now seems to be working again albeit with a wild temperature swing in the freezer section, from -8 to -30 , would that be normal ?

Alisiri 1 reply Thanks to this blog I have a working fridge again and I know a lot more about how they work. When I got up this morning the fridge was fully functional again, having come back on during the.night. I think it happened because I was doing a lot of baking and may not have been bothering to fully shut the fridge door while I was going back and forth. I also had the oven on very high and it is right beside the fridge - not a good piece of kitchen design. The defrost took a full 48 hours. Meanwhile the 30 year old frost free that lives in tha garage was a life saver. Thanks again

Thanks to this blog I have a working fridge again and I know a lot more about how they work. When I got up this morning the fridge was fully functional again, having come back on during the.night. I think it happened because I was doing a lot of baking and may not have been bothering to fully shut the fridge door while I was going back and forth. I also had the oven on very high and it is right beside the fridge – not a good piece of kitchen design. The defrost took a full 48 hours. Meanwhile the 30 year old frost free that lives in tha garage was a life saver. Thanks again

Washerhelp

Likely replying to Alisiri

Thanks Alisiri: If you are doing the 24 hour defrost it should be left unplugged or it will come on before it’s fully defrosted. The fan would start up as soon as it became free enough but there would still be loads of ice around and the fan wouldn’t need much more to jam it up again.

If the fault reoccurs do a full defrost with door open and no power..

mICHAEL 1 reply Researching a problem for my sister in law, has with a 2 month old Frost Free FF making a noise, I found the answer in the above & thank you for your nefforts in answering such questions.

Researching a problem for my sister in law, has with a 2 month old Frost Free FF making a noise, I found the answer in the above & thank you for your nefforts in answering such questions.

Washerhelp

Likely replying to mICHAEL

Thanks Michael:

Jackbowles: The water created through defrosting should run down a channel on the back wall inside the appliance and then into the back of the machine where it runs into a drip tray on top of the compressor pump and evaporates. If it’s not doing that the hole at the base of the channel may be blocked.

You might be able to download an instruction book here Appliance instruction books and manuals

Ike 1 reply darn! my fridge wasn't working at all. the freezer portion was operating but at a diminishing capacity. the repairmen said they needed to replace two circuit boards. now that i read your article, i probably could have fixed the fridge with a 24 hr full defrost. maybe all they did was check the evaporator for ice after the overnight power off defrost they started. could i have done all this myself instead of paying them all that money? or are circuit board replacements a for real fix?

darn! my fridge wasn’t working at all. the freezer portion was operating but at a diminishing capacity. the repairmen said they needed to replace two circuit boards. now that i read your article, i probably could have fixed the fridge with a 24 hr full defrost. maybe all they did was check the evaporator for ice after the overnight power off defrost they started. could i have done all this myself instead of paying them all that money? or are circuit board replacements a for real fix?

Washerhelp

Likely replying to Ike

Hello Ike: A faulty pcb can indeed cause these issues. A 24 hour defrost can cure the problem if it’s just iced up around the fan motor due to the door being left open too long, but the fault can often return even if a full defrost gets the freezer working again if the icing up was caused by another fault on the appliance such as a faulty sensor or pcb.

Even if the pcb was the cause they would still need a 24 hour defrost to clear the ice around the fan chamber.

Washerhelp 1 reply Jopaco: Do they not mean the black condenser at the back of the machine which is open to the air and gets very dusty? The gas passes through and loses heat there and attracts a lot of dust. I wouldn't have thought a part concealed under a backplate would get any dust.

Jopaco: Do they not mean the black condenser at the back of the machine which is open to the air and gets very dusty? The gas passes through and loses heat there and attracts a lot of dust. I wouldn’t have thought a part concealed under a backplate would get any dust.

Mags

Likely replying to Washerhelp

Hi Washerhelp

Thank you for comments, very helpful.

I have a Prestige PRT 325 FFCS my fridge has packed up I have tried turning off the fridge and leaving the freezer as that is functioning ok but still not cooling. Have seen some terrible comments on this model from another site. Is it worth calling an engineer. Had this one for 3 years.

Gjorgji 1 reply I am considering on buying a fridge freezer. On some of them there is a sign "No Frost" and on some "Frost Free". Is that the same? And another question: Is it better the freezer to be on top (freezer top), or on bottom (freezer bottom)? Thank you in advance

I am considering on buying a fridge freezer. On some of them there is a sign “No Frost” and on some “Frost Free”. Is that the same? And another question: Is it better the freezer to be on top (freezer top), or on bottom (freezer bottom)?
Thank you in advance

Washerhelp

Likely replying to Gjorgji

Hello Gjorgji: It’s possible some manufacturer’s are using the different phrases to describe the same product. Logically the terms “no frost” and “frost free” should mean exactly the same thing. You need to check with the sales people if there is any difference. If there is I’d like to know and would write an article specifically about it to clear things up.

Regarding the position of the freezer as far as I know it would be just down to personal preference. Most people are likely to prefer the fridge on top as they are likely to use it frequently each day but maybe someone frail might prefer the freezer on top if they found it easier to load and unload. Come to think of it I didn’t even know you could get one with the freezer on top. If it was a tall one you’d need step ladders to get to the top drawer.

Sylvia 1 reply Firstly thanks for all the great advice on here! We just got our new AEG frost free fridge-freezer today, and was concerned about the the noises it's been making since switching it on - I can only describe it as strange scraping-like sounds that vary in noise level. Is this a normal noise? The other thing I'm a bit worried about: it's supposed to have a charcoal air filter in the fridge, but never came with one. Is it essential to have one of these or is it ok to operate without one? Thanks for your help!

Firstly thanks for all the great advice on here! We just got our new AEG frost free fridge-freezer today, and was concerned about the the noises it’s been making since switching it on – I can only describe it as strange scraping-like sounds that vary in noise level. Is this a normal noise?
The other thing I’m a bit worried about: it’s supposed to have a charcoal air filter in the fridge, but never came with one. Is it essential to have one of these or is it ok to operate without one? Thanks for your help!

Washerhelp

Likely replying to Sylvia

Hi Sylvia: Thanks very much. You can get lots of strange noises from modern fridges including whooshing noises, the sound of something liquid running through pipes and even the occasional loud cracking sound. Obviously any noise that suddenly starts and continues may be cause for concern but when new you don’t know what it should sound like. I can only advise to see if it settles down and use your judgement as if it sounds like something is wrong or not.

A charcoal filter would only be to help reduce food smells. It might be useful but not essential.