How do they work?
Frost free fridge freezers are very popular and auto defrosting fridges are a great convenience. In a frost free appliance the cold air is blown round the freezer using a fan. On modern refrigeration the evaporator (which is the plate that gets cold) is hidden behind the plastic wall inside at the back of the food shelves. When working correctly you can usually see small beads of ice randomly scattered on the back wall unless it’s in a defrost cycle when you may see water.
Heater inside
the 
Believe it or not most modern refrigeration has a heating element inside. This heater is used to defrost the appliance automatically. During the defrosting cycle the ice on the back wall melts and runs down the back wall into a channel. It is then directed through a hole out through to the back and runs into the evaporator tray. The evaporator tray is on top of the compressor which gets pretty hot and evaporates this water into the air.
Because the evaporator is behind a back panel the cold air has to be blown around the compartment with a fan motor. The defrost cycle also needs sensors and a timer and combined with several sensors throughout and PCBs to control everything the result is there is a lot more to go wrong than there used to be in old-fashioned conventional fridges. However, they are still fairly reliable.
Common problems with frost free fridge freezers
If the door is left open for too long (especially in humid conditions) the evaporator freezes over and the unit will not keep the food cold. This problem (unlike the older machines) has a greater impact because you can’t see the amount of ice built up around the back of the panel hiding the evaporator.
In many frost free fridges the ice can form all the way round the fan and cause it to run slowly or even seize up. Prior to seizing up the fan may catch on the ice and make a high pitched noise. This will of course result in the fridge or freezer not getting cold. If you hear a strange noise from your frost free fridge freezer which sounds like something is catching on a rotating fan it could be due to ice forming around it.
If it stops working due to ice forming behind the evaporator and round the fan then defrosting the unit manually can fix it but it involves unplugging the unit for at least take 12 hours or so.
You may not see much frost as it would be behind the back wall or behind the fan unit.
You can’t really use a hair dryer on modern units because they may have a thermal fuse which protects the defrost cycle.
Also, even just getting to the evaporator to defrost it can be a mammoth task especially with some of the new American-style fridges.
If a fault re-occurs later it could be due to faulty sensor but if the fault was only due to the door been left open for a few hours accidentally then a total defrost could work. This demonstrates the type of problem many people have when confronted with these larger bulky hoses with specific fitting instructions as described in the main article on the left.
Water or sheet of ice inside fridge
If your fridge has two sloping channels at the back wall and a hole in the middle this is designed to channel the water created on the defrost cycle through to the back of the unit where it runs onto an evaporator tray which can get blocked. More details on this here- Ice or water in base of fridge or freezer.
Whilst we are on with American style frost free fridge freezers, because the doors are so big and can store so much, the opportunity to overload them is greater. This too causes warm air to pass into the unit and frost it up.
Remember a frost free unit will not cope with too much ice on the evaporator so greater care must be taken to use it correctly and check the door seals regularly.
Summary
It’s common knowledge that most people rarely read the instruction book supplied with their new appliance. This is particularly true with something like a fridge or freezer. It’s easy to imagine most people thinking you only need to plug it in, leave it plugged in, and fill it with food – what’s to know?
I would advise anyone with a modern refrigeration appliance, especially the American-style fridge freezers, to carefully read the instruction book. Modern frost-free refrigeration units work very differently to a conventional fridge or freezer. It’s even important to learn how to stack them properly otherwise you can prevent the air from circulating inside and cause warm spots.
You would be surprised at what you can learn from reading the instruction book of an appliance you already know how to use. Many User instruction manuals can be downloaded here.The page concentrates on washing machine manuals but links to appliance manufacturer sites where users such manuals for fridges, freezers and other appliances should also be available.
Repairs
Fixed-price repairs, Pay monthly options, Repair & protect your whole appliance..
Save Money Now
Subscribe to Which? today and start saving money now. Subscription offers often available.
Spares
Spares4Appliances is a spares company run by repair engineers who understand all about spare parts for appliances.
Carol: The noise could be the fan catching on ice, especially if it’s a high pitched sound, which eventually stops dead. You could try a 24 hour defrost leaving door open, but if it cured it and the noise returned or if it didn’t make any difference you’d need an engineer to look at it. ( Appliance Repairs)
hello, my 15-yr.old GE fridge [the label says “no frost”] was not freezing anything in the freezer & the icemaker was not working. a repairman came out & said it needed a new “defrosting system” [later he said it was a new thermostat]. he said to unplug it for about 24 hr. & he came back & fixed it. that was about 4 days ago. it seemed to be working but then today i noticed some frost accumulating again on the back wall of the freezer . . is some frost normal? should i call the repairman back out? Help! thanks!
Sharon: If it’s 15 years old it may be different to modern freezers. If you have the instruction book see what it says. If it has automatic defrosting on the freezer it may be normal.
With automatic defrosts the back wall should get a covering of small globules of ice or frost, which when the defrost cycle takes place turn to water, run down the back wall into the v shaped channel at the bottom and run out through to the evaporation tray on top of the compressor.
Alternatively if the door seal is letting air into the freezer it could cause moist air to be constantly drawn in which will turn to frost (as mentioned in the main article).
Hi Guys, thanks for your advice. I have pulled the fridge freezer out and had a good listen to the noise which is a high pitched whine which does stop suddenly and does appear to be coming from the fan area. It starts after the compressor has been running for a few minutes. There is no noise coming from the compressor. The contents of the freezer are frozen perfectly ok. If I knock the unit hard, the noise stops for a bit. I am reluctant to do a 24hr defrost as I have nowhere else to store the frozen food. I bought it on the internet, do you still think I should contact the supplier or can I do anything myself?
Thanks, Carol.
Carol: If it was encased in ice and the fan was jamming up it should start to affect the performance of the freezer as they rely on the fan to circulate the cold air. If the freezer is working perfectly ok the noise may be a faulty fan rather than being encased in ice. If it was encased in ice though many engineers will just charge the call out and tell you to defrost it for 24 hours and call them back if the problem returns.
If it’s making, as you say, “an awful whining noise, getting higher and higher and then suddenly stops” it sounds like it needs looking at under guarantee before it packs in altogether.
Carol. Sounds (excuse the pun) like faulty fan bearings to me, if so then sooner or later the fan will fail and the cold air will stop circulating. I would follow Washerhelp’s advice (re invoking the guarantee) – it’s going to be better to deal with the problem of where to temporarily store your frozen food at a time of your choosing, rather than when the fan finally fails.
Maybe Washerhelp could help concerning warranty. I think, although I am no expert, that with the freezer being essentially new, you can demand a replacement freezer – then you would not have the problem of the temporary storage of your food.
I agree DIYer. As it’s only 6 weeks old it’s covered by the sale of goods act that states if a fault occurs under 6 months it is deemed to have had an inherent fault when sold and you should be entitled to a refund or replacement from the retailer.
However, the same legislation also says that if the retailer can show it is disproportionately expensive to replace it rather than repair it they can insist on doing a repair. This is likely to protect retailers from the expense of replacing a product if it can be quickly and simply repaired. It would be daft for example to insist on a new machine if it only has a wire come off or a small part that they have in stock and can quickly fit without much effort.
If a repair is going to cause a lot of inconvenience or going to take an unacceptable amount of time you may want to try insisting on a replacement or even refund.
On the other hand if they say they can repair it without you having to defrost it you might be happy to allow a repair.
[ related: EU 2 year guarantee. Sale of Goods Act gives us 6 years to claim for faulty appliances ]
My freezer works like fridge and after reading the comment on your site, i checked the freezer and found ice on the inner plastic. Do i need to defrost it to work as a freezer again or something else is wrong? Thanks.
I am getting a small table top freezer that is not frost free. Reading the above, I am wondering if introducing a small fan into the freezing compartment will make the freezer frost free? If so, where would I get a small fan that will work inside the freezer? Battery or mains?
Thanks
G
tus: You could try a 24 hour defrost. If the fault is cured but returns soon after you need to get an engineer to look at it Appliance Repairs
gon: No, frost free is achieved by fitting the evaporator behind a plastic wall and away from the insides of the freezer. The fan blows the cold air into the freezer compartment. In a normal freezer the evaporator is exposed inside the freezer.