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.
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My problem started when we discovered that we could not close the freezer door. This was because the back panel had been pushed forward (by ice behind it, as it turned out), forcing the food drawers forward.
I took off the back panel (next time I have to do this I will turn off the freezer for a couple of hours to prevent ice sticking to the back of the panel and damaging the foam insulation). On removing the panel I discovered that the bottom half of the evaporator was solid with ice, the top half completely free of ice/frost.
It took ages to melt this ice, even using warm air from a hair dryer. After a while, the water drain came into view, and the melting water went down it, no problem. There had been nothing blocking this drain, apart from ice! When all the ice had melted, I replaced the back panel (with restored foam insulation) and everything is now perfect – apparently – time will tell.
But, how did the drain get blocked with ice in the first place?
Now, my freezer (a Hotpoint FZA80) has a ‘fast freeze’ button. I guess this cuts out the defrost cycle when it is used – and this means that when the freezer returns to normal operation the first defrost cycle will melt a lot of ice, perhaps with chunks falling off and blocking the drain hole. What say you? Should I advise my wife to stop using the fast freeze button?
Hello DIYer: I would have thought using fast freeze should only freeze up the hole if it’s already blocked and already full of water. Otherwise it shouldn’t cause any problem.
Frost free refrigeration relies on the defrost cycle warming up the ice and having it run down the back wall and collect in the runners that channel it to the hole in the centre. From there it runs out to a tray on the main compressor (which gets naturally hot) and evaporates. Frost free freezers can suffer from the hole getting blocked up which can cause future water to run into the base of the fridge instead and freeze up.
Our top of the range AEG frost free freezer is almost 3 years old. We never take out those extended warrantees so it is not covered. It has had a mind of its own recently, with its alarm going off, its temp varying between minus 10 and minus 20 despite being set at minus 18 and finally I called the number on the instruction book. Was advised to take out a year’s extra cover for £160 and the engineer came today. Had already parked the surviving food with neighbours and had a clear-out of the dross. Needless to say, once empty it was behaving perfectly. The engineer said ‘frost free’ does NOT mean don’t defrost. He showed me the frost buildup behind the grill at the top of the fridge. He advised me to turn it off for 24 hrs, clean it out (it looks perfectly clean) and restart. He practically guaranteed that it would be ok. Why on earth don’t they mention any of this in the manual? I am going to have a go at AEG but no doubt will be fobbed off. We are two adults who use the freezer and we do not leave it open for long. I am furious that such a simple remedy has cost me £160 – I could have paid a call out fee of £70 plus VAT but didn’t quite dare go for this option in case it goes beserk again. Will keep you informed, but be warned and do defrost your frost-free about annually. What a bore.!
Defrosting a frost free freezer. Beware a flood. If it’s like mine, there is nowhere for the melted ice to go until the hole mentioned by Washerman is free of ice or of any other blockage, therefore until this hole is free it will overflow and end up on the floor! and even when the hole eventually becomes clear, the melt water will go to the tray over the compressor, fill it, possibly overflow and cause more agony.
Defrosting takes a long time – have your mop ready.
Kirsty: Frost free does mean you shouldn’t have to defrost, if it’s not mentioned in the manual that proves it. If a fault develops, ice can form, or it can form if the door is left open accidentally in which case you would need to defrost it but in normal operation it shouldn’t create any ice.
Unfortunately with frost free freezers the ice forms out of sight so you aren’t aware it’s there but whilst ever it is the freezer wont function properly. They also take a long time to defrost for the same reason, the ice is packed around the fan or evaporator which is being insulated panels. A minimum of 12 hours defrosting is needed and possible even longer depending on ambient temperatures.
DIYer: I would also enlist the use of some large towels.
Washerhelp. See #31 and #32. Due to the construction of my freezer there is absolutely no way the the drain hole can be blocked by anything other than ice – so the origin of my problem is still a mystery. (My actions under #31 seems to have succeeded). I can only assume we left the door open inadvertantly for a lengthy period. Even so, with no foreign matter blocking the hole, I can only assume that a chunk of ice fell off the evaporator during the defrost cycle and lodged in the drain.
Maybe it depends on which direction the fan blows!. I would like to think it draws cold air from the evaporator and blows it over the food trays and not the other way round. (I’m suspicious since my manual says that the lower trays are the best ones for getting a faster freezing rate, suggesting that the fan pushes air past the evaporator so that the emerging cold air hits the lower trays before the upper ones – the snag with this is that the air would encounter the drain hole almost immediately after passing the evaporator.) Either way, some of this cold air must go down the drain hole so that if there is a parial blockage due to a fallen lump of ice, then this current of cold air may make the blockage complete.
Many thanks for your excellent site – without it I feel sure that like Kirsty, (#33) I too would have been stung for £160 or so. Thank you.
DIYer: Thanks. The lower trays should be colder because of the cold air being heavier and congregating more at the bottom, just as in an oven where conversely the hottest air is at the top.
Hi, can you advise please, I have a Bekko frost free fridge freezer, only 6 weeks old which makes an awful whining noise, getting higher and higher and then suddenly stops. The motor seems to come on every 20 minutes or so for about 8 to 10 minutes although I only have the thermostat set at number 1. Is all this normal.
Thankyou.
Carol. Can’t really help you with this. More details needed. Does the freezer actually deliver the goods – that is, does it freeze your food at the right temperarure. If not then I suggest you get on to your supplier, otherwise, how noisy is it? maybe the compressor is noisy when it is active. There is no whining noise from my freezer, whatever it is doing. I think you should raise this with your supplier, presumably your freezer, six weeks old, is still within warranty. I feel sure Washerhelp would agree. If they fob you off (as Phillips did with me over a DVD player) fill out a small claims court action. Phillips succummed immediately despite their prior adamant denial of any responsibility.