Dishwasher Fault Finding

How To Repair A Dishwasher

It amazes us constantly how people think that a dishwasher is a desperately simple device, in some ways it is, but other than a drum and bearings (although other parts make up for them) there are as many parts in a dishwasher as there is in a washing machine. In fact, a dishwasher can often be more complex and expensive to manufacture than a washing machine!

Safety First When Carrying Out A Dishwasher Repair

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. If you are unsure in any way, call in professional help and follow our basic electrical safety guidelines.

Under no circumstances live test or operate machinery with the casing open as it can and has proved fatal. Do not become another statistic!

To get the best possible service we would recommend our appliance engineer search 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.

A typical dishwasher inside showing baskets and cutlery basket

Dishwashers (Dish), refrigeration (Cooling) and cooking appliances are covered in separate guides to keep the list manageable.

Do bear in mind that, like the other guides in this series, the instructions and possible causes are based on a very wide range of appliances and any one fault may well not pertain to your exact appliance.

Dishwashers are constructed as a big empty tank (usually stainless steel but sometimes a resin or plastic) into which you place cutlery (in a basket) and plates on the racks. This means that all the bits that "do stuff" are around that big empty space, this means that they are crammed into small spaces and it can be hard to work on these machines, as well as dangerous as some of the edges are literally razor sharp, so great care is required.

Normally all the main electrical components these days will be located in the door and in the base, below the bottom of the inner tank. Access is normally gained by the way of an inspection panel at the front and/or back as well as removing the inner door.

Remember it's cramped, it can have sharp edges, moving parts and can carry a current, even when switched off with the plug out, so take care.

Common Dishwasher Problems

Dishwasher won't start or power up

I suppose getting the first "that could be almost anything problem" out the way first is probably best. This could be almost anything...

First things first, check the electricity supply and also the fuse in the plug. If the machine is integrated (built-in) you may be about to find out how idiotic some kitchen installers really are as, more often than not, the plug will be behind the machine and you'll have to drag the whole lot out just to change the fuse.

Obviously you would now check the mains cable and also the mains terminal block to make sure that they're okay.

Next, as with the washing machine, you need to locate and check the mains filter which will look like a capacitor but with more terminals on it. Be careful, mains filters and capacitors can retain a charge even when power is totally removed and should be discharged to make safe before testing.

After this we're into the realms of PCB's or timers, possible wiring loom problems (common where the wiring is fed through the door) and the obvious main on/off switch.

  • Plug, socket and fuse
  • Mains cable and terminal block
  • Mains filter
  • Door wiring
  • Main on/off switch
  • PCB or timer
Dishwasher lights flash or error code displayed and won't start

This will, in almost any dishwasher from the past decade, be a fault code of some sort which have been much discussed within the forums so please search there first for an answer. The dishwasher is basically telling you that it has detected a problem of some kind and that, without a resolution, it cannot continue with the program. Very often this sort of error will result in the dishwasher being totally inoperative and it will not accept a program at all.

Without knowing what to check and what the error being displayed is it is virtually impossible to offer any sort of guidance as the codes vary, not just between various brand names, but even from model to model.

Dishwasher noisy

When reported this fault will depend on several factors, the main ones being what sort of noise, when in the program and what machine it actually is. So there are many variables here.

However, things to check would be:

  • Spray arms or mounts faulty
  • Main recirculation motor
  • Drain pump faulty
  • Drain pump jammed or object trapped
  • Object in main recirculation impeller housing
Dishwasher won't drain water or empty

Yet again this can vary from machine to machine but, in general, it will signify a fault with either the pump or the house plumbing. The reason that it can vary is that some dishwashers use the recirculation motor in reverse to drain the tank, so it can mean that the main motor is faulty and that there actually isn’t a drain pump fitted at all essentially as a cost-cutting method in our opinion.

  • Drain pump faulty
  • Drain pump jammed or object trapped
  • Object in main recirculation impeller housing
  • Main recirculation motor
Dishwasher won't wash

We get this fault reported as shown in the question but it can often signify a number of possible failures.

What we often find is that what is actually meant is that the spray arms are not turning or are not turning well enough to really do much of anything. Of course this can be caused by many things, lots of which are very much dependent on both the make and model of the dishwasher.

The most common, on machines where there is a capacitor for the motor, will mean that the capacitor is faulty and the motor is running weak or slow.

Another possible cause is that the "tube"has split internally on machines where that is used. This is the "C" shaped water delivery tube that feeds the upper and lower spray arms on some models, when it splits there is a loss of pressure to the spray arms and therefore you get a drop in spray pressure and the dishes are not washed correctly. The same effect can be seen by the spray arm housings splitting on some models.

However, probably the most common cause of this is the main recirculation motor with either the capacitor faulty, the main pump impeller jammed or broken up as most of them are made from plastic or the main motor itself being faulty.

  • Spray arms blocked
  • Pressure loss
  • "C-Tube" split
  • Motor capacitor faulty
  • Main recirculation motor impeller jammed or fault
  • Main recirculation motor faulty
Poor wash results from the dishwasher

First thing to be doing if you have poor wash results is to look at the filters and also the spray arms, there is an article devoted to the subject that you can read from this link

There is also another article which explains all about load patterns, spray arms, detergents and a lot more which you can access from this link

Those articles will outline the most common reasons why dishes being dirty are a common complaint because, all too often, it is a case of user error, not a fault on the dishwasher's part. Of course it can be, but you'd be better to eliminate the obvious before either delving inside the machine or calling an engineer.

The dishes have grit on them, what's that?

This must be the number one complaint we get on the phone about poor wash results in a dishwasher. Loads of people seem to think that, somehow as if by magic, that the dishwasher can create grit or sand on the dishes. The sort of it is that it can't and doesn't, this is in 99.9% of cases simple user error.

It is in fact so common that there is an article devoted solely to the one problem which you can read from this link

The dishwasher is leaking from the door

A leak from the door can be as straightforward as a faulty seal door seal but, in some cases it's not quite so simple and we are often asked for door seals which we will supply quite happily, only for the owner to discover that wasn't really the problem.

You see there's a commonly held belief that water comes into a dishwasher and that it rises above the bottom door seal, this is not so. What actually happens is that the water is supposed to stop filling before the bottom door seal is even reached by the water. The door seals are actually splash guards if you like, not a totally watertight seal as you would find in a washing machine.

What can and, does, happen is that cheap plastic spray arms will split and the water is misdirected towards the seal directly, which the seal was never designed to cope with and... leak. We get asked for a new seal which doesn't solve the problem as that wasn't the cause in the first place. This is also part of the reason why we encourage people to ask about a lot of the spares we sell as we often do offer advice and help.

Of course if the water gets above the seal, i.e. the dishwasher overfills, then it will almost certainly leak. This would indicate a problem with the pressure switch or sensor.

Whilst not entirely definitive things to look for would be as follows:

  • Spray arms split or faulty
  • Door seal damage, both lower and "goalpost" seal or gasket
  • Overfilling
  • Correct detergent use (overfoaming)
The dishwasher is leaking from underneath

This is, again, one of those faults that can be pretty much anything as there's two things to bear in mind here. Water flows down with gravity so you first of all have to determine the source, not the result and also that almost all the "wet" parts of the dishwasher are in the base as we said earlier. So sometimes finding out where the leak is coming from can be difficult but to put the fault right, that is what is required.

Possible common causes would include:

  • Pump faulty, leaking
  • Main recirculation motor seal leaking
  • Hose failure
  • Sump seal
  • Regeneration chamber
  • Overfilling
  • Incorrect detergent use (overfoaming)
The dishwasher went on fire!

Okay so this isn't just so common these days, but it can still happen and it is worth a mention.

It is sad but some people make a mountain out a molehill, you get a puff of smoke and immediately the appliance has "gone on fire" and it's some sort of emergency. Sorry folks, fire means flames and not a bang accompanied by a puff of smoke or a whiff of an electrical component burnt out. An actual fire on any appliance is extremely rare really although it can and does happen.

Normally though when we get this fault reported it will turn out to be nothing any more dramatic than a burnt out capacitor or the door wiring has shorted.

The dishwasher wont' fill

Assuming that there are no error codes being thrown up the most likely cause will be the inlet valve, these are usually not too hard to replace although some do have a pressure switch attached to them.

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