Tumble Dryer Basic Fault Finding

How To Repair A Tumble Dryer

Repairing a tumble dryer is often a relatively easy task for most people reasonably competent in DIY and working with electrical products as they really are rather simple appliances all things considered.

Of course things get a little more complex once you step up from simple plain old vented tumble dryers to condenser tumble dryers and finally (for now) to the much newer low energy use heat pump tumble dryers.

Vented tumble dryers are the oldest of all types and, generally, the most reliable and the easiest to repair when something goes wrong. This type requires a vent hose to be fed to the outside through a wall or window so are easy to spot.

The next up the ladder is a condenser dryer which have become far more commonplace because they can be installed without the requirement to have a vent to the outside. However, it should be noted that these cannot be installed just anywhere and there are restrictions on temperatures and that cleaning filters regularly becomes essential.

Now we have low energy heat pump tumble dryers which are, for the domestic whitegoods industry, a relatively new technology although these types of tumble dryer have long been in use in commercial applications and the actual technology is far from new.

Heat pump tumble dryers work largely on the same principle as a condenser tumble dryer but with a few notable differences, the largest being that instead of a heating element as such it uses a small heat pump, much like a refrigeration unit, to provide heat to dry laundry.

To correctly diagnose a tumble dryer fault you will need to have a grasp of how your tumble dryer works and the main components of the dryer. Of course how these are implemented can vary hugely from brand to brand and even from model to model but the principals will remain almost constant.

How A Tumble Dryer Works

There are three basic types of tumble dryer in common domestic use, the condenser dryer, heat pump tumble dryer and the vented dryer. To find out more about the pros and cons of each please refer to our tumble dryer buying guide which will explain more about each type.

In short the vented dryer requires a vent to push the hot exhaust air out of the room in which the dryer is operated and this is normally to the outside either through a wall or window by way of a venting kit or hose.

A condenser dryer is "self-condensing" meaning that the moisture removed from the clothing during the drying process is condensed internally and the water vapour either drained to the house drainage system or collected in a container which has to be manually emptied.

In both cases the basic operating principles of the drying action are pretty much identical and so the rest of this explanation is generalised.

When it comes to faults on a tumble dryer, of which not heating is by far the most common, like all other appliances you need to methodically determine where the fault lies and so you have to understand how the machine works to do that. Simply guessing and blindly replacing parts until it works again is not the way to go about things.

In any dryer there are three things that must be present for the machine to be able to dry, heat, mechanical action and airflow. If any of those fail in any way then the dryer will not dry.

Tumble Dryer Heaters And Thermostats

The heater and thermostats are the most common area to fail in some way. Normally this will be a case of simply determining which has in fact failed which is normally quite easy by simply testing the heater elements for continuity using an electrical meter. If the heater is open circuit it will require to be replaced, bearing in mind that many are in fact two elements for the different levels of heat, so check both circuits.

If the heater is not open circuit and you have continuity then you should then look at the thermostats. Normally there are one o possibly two mounted around the heater housing but there are also often another one, possibly two, cunningly hidden on the vent, this is commonly known as the "exhaust stat". It's not so common that an exhaust stat will fail but,

it does happen and how you determine the part faulty as an amateur is difficult at best as usually we will apply some heat whilst we have a meter on it to check that it turns on and off as required.

The usual two thermostats at the heater itself will usually be a cycling thermostat and the other an overheat stat, sometimes referred to as a TOC (Thermal Overload Cutout).

The cycling stat controls the normal dryer operation cutting in the power to the heater as and when more heat is required whilst the overheat thermostat simply does nothing until an overheat condition is recognised by it.

It is increasingly common to find these overheat thermostats have failed or, in actual fact, have operated correctly. The overheat thermostat is in effect a safety device designed to stop the tumble dryer from overheating and, possibly, catching fire should a failure of the main cycling thermostat occur or the airflow in hindered in any way. However it is common these days that these have "tripped" with no other problem to be seen. The reason for this is almost invariably that the user has opened the door before the dryer's cooldown phase has been completed. This causes latent heat to build inside the dryer thereby raising the temperature enough to trip the overheat thermostat.

Many of these thermostats are now of the non-resettable type and therefore must be changed to resume normal operations. Under absolutely no circumstances should an overheat thermostat be by-passed, fitted incorrectly or modified or you could have a serious safety risk.

We made a short video on how to test tumble dryer thermstats which is here:

Airflow Through Your Tumble Dryer

As stated previously, in order to operate correctly your dryer needs a constant flow of air.

This is true both internally and externally!

Diagram showing the airflow pattern in a condenser tumble dryerWe cannot stress enough how important airflow to a tumble dryer is. If you kill the airflow you will kill the tumble dryer.

Simply put, a tumble dryer draws in cool ambient air, heats it over and electrical (in most cases) heater and then "blows" that air through the clothes to condense the water content and then exhausts that out the vent.

If you do not have a sufficient supply of air coming in then the dryer won't work correctly. If you do not have adequate airflow out then the water vapour and expelled air have nowhere to go and, the dryer won't work correctly.

On a condenser dryer the main difference is that the expelled air will pass over a condenser (hence the name of condenser dryer) which will condense the expelled water and usually pump or drain that water to a tank which can then later be emptied. This saves the need for an external vent but does complicate the appliance somewhat.

Common airflow problems are usually not that hard to track down and the usual complaint in this area would be poor drying performance or complaints that the dryer takes ages to dry clothes. Interestingly poor airflow is very likely not just to decrease the performance, increase the drying time but it will almost certainly mean much longer running times which will cost you a lot more in electricity. It is very worthwhile checking the dryer on a regular basis to ensure that the airflow is good.

Check the filters first, blocked filters will mean reduced airflow and this can seriously affect the dryer's performance. This is simple routine maintenance that, if not carried out, will mean possible poor performance, longer dry times and bigger electricity bills.

Externally make sure that the dryer is not completely encased. All dryers MUST have a good supply of air around them or you will almost certainly have problems. Whilst this should be noted upon installation it may often not come to light for months and, in some cases, years before it causes an actual failure.

Where the dryer is vented the vent must be clear and unobstructed.

Common Tumble Dryer Faults

No heat in tumble dryer

This is the most common failure reported, often with a simple solution on inspection.

If the machine does not heat check for a reset button usually a small red button on the back and see if the machine works after this is pressed. These are almost always fitted to appliances manufactured by Crosslee who make tumble dryers for just about everybody from Candy to Zanussi so it's worth having a look.

  • Heater faulty
  • Thermostat or thermostats faulty
  • Blocked with ooze or fluff
  • Safety thermostat tripped
Tumble dryer drum not turning

Again a fairly common fault to come across and, in the case of tumble dryers a faulty belt is not at all uncommon.

  • Belt faulty
  • Motor capacitor (where fitted)
  • Motor faulty
  • Jockey wheels faulty
Tumble dryer noisy

It's again not uncommon and usually fairly straightforward to find the problem however, solving the problem however is often is far from easy.

  • Bearings faulty
  • Jockey wheels faulty or worn
  • Felt pads worn
  • Motor bearings faulty
Tumble dryer not starting

This is not really a very common problem on most but some machines and older machines especially it does happen usually due to the door microswitch failing. It can also be caused by a timer failure, but that is unlikely.

Other problems include steam, if you get steam then your appliance is not vented properly or the vent hose is broken in the main. But if you just hang the hose out the window it could well be that the condensed air is being blown back into the room!

Bad smells from a tumble dryer are almost always caused by the vent hose having a dip in it where water gathers ad goes stale, it could be worth checking.

Well that about covers standard dryers any other faults really require the services of an engineer.

Self Condensing Tumble Dryers

These appliances are lot more complex and for the layman, not really to be tampered with unless you either know what you're doing or are confident in your own abilities.

If the appliance leaks check that the water tray in it's housing correctly and in not full.

If you get steam from the appliance it may be that the room is too cold make sure that the room temperature is within the limits in the instruction book. This can also happen with a normal dryer too especially if the room is too cold.

The common problems are pretty much the same as they are for the normal dryers, but with the added complications of a condenser system. That said, make sure that the condenser itself is clear, many can be removed and cleaned.

The Big Warnings For All Tumble Dryers

Let any dryer run through it's cooldown phase!

Pulling the door open to check if stuff is dry and such things will, almost certainly in a modern dryer, result in the overheat thermostat being tripped and, many are now "one-shot" devices meaning that they won't and cannot be, reset.

Make sure filters are clear and regularly cleaned. Failure to do so will cost you both time and money.

Ensure adequate ventilation and a ready supply of fresh air, if you don't you will have problems.

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