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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Gary: Frost is caused when air gets inside and the moisture within it deposits as frost. Make sure it’s dead level as slight twists in the cabinet can cause the door seal to not fit properly letting air inside. Make sure the door seal is in good condition too. Other than that it would need looking at, it’s not necessarily connected to the previous repair.
Lesley: It sounds like you might be entitled to reject these machines under the sale of goods act as they appear to have an inherent fault. They may be able to hold back some of the money as you’ve had a certain amount of use from them but I would ask for a refund or exchange to a completely different brand. Read this article carefully Consumer Rights Act 2015 gives us 6 years to claim for faulty appliances
Emma: Modern frost free fridge freezers are quite different to the old ones. They work by blowing cold air through the appliance hence the fan. I would expect it to settle down somewhat when fully loaded and down to temperature but I couldn’t say how often it should come on. Once down to temperature and full of food though unless the door is opened it ought to maintain temperature for reasonable lengths of time.
hi i have a hoover fridge freezer frost free freezer working ok but fridge is cold but just cold the back wall of the fridge seams to be wet all the time no ice on the back wall can enyone help pls
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.
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
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.
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!
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).
Hello,
I have a PRESTIGE PRT295FFCS fridge freezer. I have never had any problems with it until last night all of a sudden the freezer started warming up for no apparent reason.
I checked the door was closed properly, removed a layer of ice from the bottom & put the ‘super freeze’ on to try to get it back to -18, but nothing has made a difference. It is now at +1.
I can’t find my user manual to check in there, any ideas?
Any help would be much appreciated!
Amanda: It sounds like it’s just developed a fault. I don’t think the instruction book would help, you need an engineer. If it’s been placed in a cold environment it could account for it but I wouldn’t have thought it was that cold at the moment – How are fridges and freezers affected by the room temperature?
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?