Often, especially with older machines, belts are often blamed as being a problem on machines when in fact they often are not.
This is especially the case on washing machines and washer dryers where an induction motor is used, that is one that does not have carbon brushes fitted to it. The reason is that washing machine belts tend to outlive the machines themselves, they are very robust parts in the main and designed for a long life. For this reason the assumption that belts "stretch" is virtually a myth as on most appliances this will virtually never happen.
What does happen is that the belts will fray, tear and be thrown off but, in 90% or more of cases there will be a reason that this has happened. Generally on more modern washers this will be due to a pulley fault or a bearing failure, something will often be causing the belt to run wide of its true path therefore causing damage or allowing it to be thrown off.
But, to get back to induction motors, many non-brush motor machines will use a simply pulley system which just like the gears in your car, alter the drive ratio to achieve the high spin speed without the need for an additional winding on the motor. This reduces the size of the motor, the heat generated, the power required and makes them cheaper. However these variable pulleys as we call them, do go faulty, a lot. When they do the belt appears to be slack or just spinning, so people often buy a new belt only to find that it is exactly the same as they one which they wished to replace, it is basic misdiagnosis.
These days it is pretty rare to see an induction motor, although some of the better manufacturers still use them as they are incredibly reliable and much quieter in operation, as to achieve the high spin speeds now demanded by people and to keep costs down brushed motors are really the only option.
But with this and the increased use of electronic control systems (some form of speed control PCB is required for all brushed motors) the belt now does something it never did in the past, now they detect an out of balance situation.
Most modern washing machines, have an electronic "out of balance" control system to protect your machine. These systems are commonplace on modern machines due to larger capacities and, primarily, to high spin speeds.
Small and light loads are very likely to make this function operate even when perhaps you do not wish it to; there is no way to disable this safety system.
This system is used to protect and prolong the life of the bearings and drum by ensuring that excessive force is not applied to either and also to stop the machine, especially at higher spin speeds, from vibrating excessively on flooring that is not solid such as "floating"wooden floors.
What will happen is that the machine will sense that the load is not evenly distributed around the drum and it will try to correct this error several times by rotating the drum trying to distribute the load as evenly as possible to allow the spin to proceed. If the machine cannot achieve this and it senses a danger of damage or excessive vibration the spin program will be aborted. It is also more environmentally friendly to wash a full wash load and more cost effective so you can save money by washing the optimum load.
How this works is that the electronics will detect speed variances in the rotation of the drum indicating an out of balance load condition, there are no vibration detectors these days, using readings from the tachometric generator in the motor (or tacho, tacho coil) and act accordingly. So the belt actually feeds back information to the electronics in a way. Clever stuff.
However, for this reason, it is vital that you get the correct belt if you need it because if you get the wrong one it can really mess up how this all works.
This is also the reason that there are a marked increase in what we in the trade refer to as "stretch" drive belts. When you get one it can appear too small but it does in fact "stretch" to fit.
So if you are replacing a belt on a modern washing machine as they do fail makes sure that you have the correct one and don't panic if it appears too small.
Please remember to keep yourself and your family safe by following our simple basic electrical safety guide. Quite simply it is not worth someone's life or an injury just to save a few pounds calling in a professional repairer.
To get the best possible service we would recommend our repairs@ service which will refer you to a local repairer that operates to a standard that we have set in our own code of practice. It is your guarantee that the service that you receive will be a quality repair that is fairly priced and guaranteed.
The problems here are frequently asked about in the forums and you may well be able to help yourself before posting a question or calling an engineer however we must stress, above all else, that your own safety is your primary concern.
First and foremost make sure that the power is off and the machine is unplugged from the mains.
This is absolutely vital as many an washing machine engineer will have a tale to tell of how his hand was slashed open replacing a belt due to the razor sharp edges and/or the power was inadvertently left on and the machine started to turn. It isn't nice and can be extremely dangerous.
With that said replacing a drive belt is a relatively simple operation assuming that this is the only fault.
Mostly they are all accessible from the rear, you will have to pull the machine out completely to allow access and remove the back panel or cabinet half. Unlike in the photo below by Ian Dales of Dales Electronic, there is no need to use force or, as in the example here, use tin snips to open up the casing!
Make sure that any remains of old belt are removed, especially around the motor pulley if the old one has frayed away as, all too often, strands of the material will wrap around the motor pulley shaft and can impair performance or even cause damage. Errant strands and faulty pulleys can also just wreck the new belt that you are about to fit, so it's well worth having a check.
Belts are fed on and many modern ones can be an absolute pain to fit as they can be extremely tight going on. Several I've done myself I was scared would snap! In other words, be very careful as if you get a finger trapped in there it's going to hurt and, if it catches a sharp edge it's going to hurt even more.
So, starting at the bottom place the belt around the motor drive pulley and bring it up to the drum pulley. Place the drive side onto the drum pulley keeping the belt taught and work it around the drum pulley slowly by turning the pulley whilst holding the belt in place. Doing it this way you have a far greater chance of success and of not getting injured.