This is a very common problem and there's quite a number of things that can cause the problem of overfreezing occurring in either a fridge, fridge freezer or freezer. I'll go through the common faults that can occur on any then to the ones that can be specific to each different type of refrigeration product.
This article should explain the basics when you get an appliance overfreezing and the likely things that you can try for yourself, but if you're unsure then you will need a professional to sort it out and please, please be safe as water and electricity are very dangerous bedfellows.
Scientifically I have no idea how many types of ice that there are, I've no need to know but what I do know is that there are two types of ice that cause problems in refrigeration products.
To know where to start looking for the problem you first have to understand what the symptoms are actually telling you. Quite often we will hear from people that, "there's a lump of ice in the fridge" or "it's all iced up" followed by, "what' likely to be wrong and how much will it cost to put right?" and, to be honest, this isn't enough information for us to be ac curate.
These days it gets still more complex as electronic controls and sensors have taken over from traditional thermostats making the chore of remote diagnostics on a fridge or freezer far harder than they ever were in the past. Like most things, technology marches on.
The first and most common of these is what looks like snow for all the world inside a freezer (or freezer section of a fridge freezer) or a fridge with an icebox in it. You'll notice that this has a "powdery" type of texture to it and is formed over a long period of time.
An example is shown in the photograph to the right.
This type of ice is formed by condensation. In other words warm air from outside the appliance is creeping in somehow, condensing when it meets the cold air inside and then forming ice. This is why it is "powdery" ice as it is formed from tiny droplets of condensing water.
If you see this sort of ice in the machine then you are looking for some sort of air ingress.
The next type is less common and is often seen on the base of chest freezers (more on that later) as well as anywhere that water leaks and becomes frozen. This type of ice formation is cause by water and will be smooth and very dense, basically like a large ice cube but often not as clear as it is formed from layer upon layer of water leaking onto the one area.
This sort of ice will always indicate some sort of water leakage whether it appears inside the unit, quite common on the likes of the US style fridges where water enters to enable the use of an ice-maker, or on the outside which can also happen.
If you see this type of ice then you are looking for a water leak of some kind.
If you now know that you've got the first type of ice you will also know that it is because of some kind of air ingress. In small under-counter fridges with an ice box this happens naturally as the outer door is opened an closed over time. Hence the need to manually defrost these units from time to time.
We honestly cannot be forceful enough on this point. The chances are that, if you go near any refrigeration intending to defrost it with a sharp implement you will kill it, if you don't you got off lucky.
If this does happen do not expect any help from the manufacturer or insurer under any form of warranty as it is treated as "customer misuse" and they will not honour a warranty repair or replacement for this fault. And we know when people have done this, it's very easy for an experienced engineer to tell.
The safest way to defrost an appliance is to allow it to naturally defrost over time and this also does do it in the most comprehensive way.
There are other tricks of course, such as sprays that melt ice (basically de-icer) and the use of hot air guns and hairdryers but using an electrical appliance to melt water is a very dangerous business and we strongly advise against it for safety reasons.
It is not extremely common but it does happen and chest freezers, especially in cold damp environments suffer from this more than most.
Should you have ice on the outside of your fridge freezer it will most likely be at the bottom, near the feet. This will be the smooth solid type of ice and has been caused by the cold air of the fridge coming into contact with the warm air outside it or from water leaking through a hole in the fridge freezer.
Some older Hotpoint fridge freezers suffered terribly from this as water leaked over time from the freezer into the insulation (the foam that insulates the cold from the warm air outside), the insulation would break down losing its ability to keep the two separate and the water that fell down as well as the condensation from the process would produce a large ball of ice at the bottom of the door. There is no cure, the machine's life is at an end.
Likewise freezers in garages or basements often suffer from this phenomena for several reasons, but the upshot of it is that most are not designed for these environments or extremes of temperature which they can be subjected to in the likes of a garage or garden shed in particular.
It is not unusual to come across a chest freezer with an ice ball underneath it, again it is terminal.
Often, if you get an ice ball on the inside, often in the inside of a fridge the situation is the same but it is worth having an engineer check it for you, he is unlikely be able to diagnose the problem remotely.
Leaking water from ice dispensers or drinks dispensers can cause solid ice either in a fridge or freezer section and this is something to look for.
Sometimes it can just be a spillage issue, but more often than not you're going to need someone that knows what they're doing to trace the fault for you. This is due to the fact that these sorts of devices are generally fitted to the like of the large US style fridge freezers and they can be technically complex and certainly not for the general DIY'r.
This is, by far and away, the most common cause of overfreezing probably equal to, if not greater than that of a thermostat or temperature sensor fault. As I explained earlier, this is due to air ingress.
Things to check for when you spot this are as follows:
If you see a gap and the door is not closing properly then they can often be adjusted slightly to compensate. It's just a case of aligning the door, or doors, again to their proper position.
It is common for people to miss this when swapping the doors from hinging on one side to the other which you can do on many fridges. Basically the door is not adjusted correctly and allows air ingress but, be aware, some manufacturers will not cover the cost of an engineer to adjust these under their warranty, as far as they are concerned this would be an installation fault, this is known as "mis-installation".
Watch out, especially on integrated fridges and freezers for the outer furniture door (the wooden kitchen door) catching on the adjacent one as they have not been aligned correctly. This is a very common problem with many of these types of appliances and again the caveat of "mis-installation" again applies.
If the door seal seems out of shape or compressed it can be brought back into shape by applying heat from a warm hairdryer for a few minutes and very often saving the need to change the door seal or whole door.
If the door seal is split or torn it will require to be replaced.
Other issues are the likes of condensation. Strangely enough this can happen when lots of fresh food is placed in a fridge or freezer.
In the photograph you can clearly see the condensation produced in the salad drawer of this Smeg fridge when lots of fresh vegetables are placed in the fridge. The reason is that, to an extent, vegetables "breath"and cause condensation.
It took us a while to work that one out the first time we saw it!
Overfreezing is also a common sign of a failed thermostat as well. But in the case of a failed thermostat the machine will just cool and cool, not cutting off when it reaches the correct temperature. In effect, especially in fridges, this will cause everything inside to freeze solid, it will not cause an ice build up over time.