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How to Diagnose Draining and Motor Problems in a Dishwasher

A faulty motor or drainage issues in your dishwasher doesn't mean that the appliance needs replacing. Instead, it's possible to fix the faults yourself at home - by following the advice in this eSpares video.

In this video, we will go through some of the various ways in which you can try to diagnose the draining and motor related problems you are experiencing with your dishwasher.

This video shows an example on how to remove or replace the part on a typical machine, some models may be different but the procedure should be similar.

What You Will Need:

Step 1 - Switch Off Your Appliance

Safety First! Please make sure that you have switched your appliance off at the mains before starting your repair.

What's Wrong? - The Dishwasher Is Not Draining At All

Cause 1: The Drain Pump

One of the main reason for the dishwasher not draining is that there has been a foreign object that has found its way into the drain pump - and has caused it to then be blocked. Such objects could include a piece of a broken glass.

If you’ve put a glass in your dishwasher and it shatters, make sure you collect all the pieces out of the dishwasher - and have a look around the filter as well - to make sure you have collected all the pieces. If possible try and establish from the pieces you have to determine whether you've got a complete glass.

If something has been washed down to the drain pump, you would often be able to hear the pump making a low humming noise after about five seconds after putting the dishwasher on a cycle. The noise is being caused by the motor due to the blocked impeller not turning.

How To Check The Drain Pump:

Start by turning off the water supply and disconnecting the inlet hose from the back of the dishwasher so you don't damage it. Proceed to lay the dishwasher down onto its back, not onto its side, and as you do be very careful to not trap the drain hose underneath.

Now most dishwashers have a removable base plate, on this one, it's removed by unscrewing the four screws. However, it's also important to bear in mind that on the other side of the base plate is an anti-flood switch.

In order for you to fully remove the base plate you will need to disconnect that anti-flood switch, so once you have unscrewed the four screws you may also need to unscrew the anti flood switch as well. There will be a screw holding the drain pump in place (it might be two screws depending on your model).

Before removing the screws, pull of the two connections that are attached to the drain pump, and then once you’ve taken the screws out you will be able to twist the drain pump and pull it off.

If any debris has found its way into the pump it'll usually be found in the area around the impeller and you can just pick that straight out when the pump is removed. Follow this by then just checking that the impeller is rotating normally (it is usual for it to rotate in a slightly jerky motion because of how the magnet works).

At this stage you can also check the inside of the chamber of the pump and screws, to make sure there's nothing blocking the pump in there.

Once you're happy with that you can double check that the pump is working normally by taking a resistance reading across the terminals.

For a normal functioning pump, you should get a reading of around about 200 ohms. Once you're happy with all of that you can just pop the pump back on.

Cause 2: Outlet Flap

If you have checked the pump and the dishwasher still isn't draining, it is worth stating that some dishwashers also have a flap that is fitted over the outlet that feeds into the drain hose - and it might be an idea to check this if your model has this.

The flap opens and closes and can get stuck, so if that's happening on your dishwasher just remove the drain hose from the pump and just check that flap for any debris that might be causing it to stick down, while also checking that the rubber isn't tacky. If you find issues with this you can choose to either clean the flap or replace it.

What's Wrong? - Noisy Pumps

Older drain pumps and wash pumps can develop quite a noisy squeal when they aged, and this is usually caused by worn bearings. If this is what you are experiencing then you need to just replace the pump altogether.

Wash pumps, generally speaking, are quite reliable but they can get blocked up as with a drain pump. If that's the case obviously remove the blockage from the wash pump. If there is no blockage then it is worth checking the capacitor, which is attached to the motor, for signs of it being burnt or having developed some bulges.

Check around the terminals and at the bottom for any burns or bulges that you might be able to find. Once you've checked the capacitor isn't damaged it may simply be a case of replacing the wash motor.

What's Wrong? - The Dishwasher Is Constantly Draining

There can be generally two causes as to why your dishwasher is constantly being drained:

Cause 1: Flooding In The Base

If there is water in the cabinet base it will trigger the anti-flood switch. If when you first put your dishwasher on you can hear it constantly draining, it may be because water has leaked into the base and has caused the polystyrene float to lift up - which then activates the anti-flood switch.

Now if that is the case you’ll obviously need to drain any water out of the base and also establish where the source of the water is coming from.

Cause 2: Drain Hose Is Lower Than The Water Level

If the end of the drain hose is set at a level lower than the water level in the dishwasher, it is going to allow the water to drain away. The water level usually fills to just below the door seal, so if you've got the end of the drain hose set to a level that's lower than that - it is going to run out of the machine.

Don’t worry if this is the case with your dishwasher though, as it can be easily corrected. All you need to do is simply lift the drain hose to a level that is higher than the water level in the appliance.

Most drain hoses come supplied with a crook attachment, and you can use that when setting the drain hose into an open pipe drain, so make sure that the hose doesn't go too far down to create a siphon effect.

Final Comment from eSpares:

Thanks for looking at this video, we do hope that you have found this helpful and hope you have been able to identify the issue with your dishwasher. Just remember though, for all your dishwasher related needs, you can visit the Dishwasher area on the eSpares website to obtain spare parts for your hob - as well as viewing lots more helpful articles and videos in our Advice Centre.


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