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Rob, Home Appliance Technician
Category: Appliance
Satisfied Customers: 6991
Experience:  20 yrs. experience with a major worldwide manufacturer.
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My Neff S5409X0GB/01 dishwasher is washing for ever, and the

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My Neff S5409X0GB/01 dishwasher is washing for ever, and the water remains cold throughout. I did see online info about heater relays, so took out the PCB but it looks nothing like the ones shown on various online guides - it looks like it's all solid state, and nothing looks burnt. It's a fairly fancy dishwasher, with touch-button controls.
Where next? I've got a multimeter, so tell me what to measure and where and I will.
If there's a way of entering a test mode I can, but I don't know how to do this at the moment.
Any parts for this look expensive from what I've seen on the neff spares website, so I'm hoping to avoid replacing parts to diagnose the fault.
If it's any clue at all, there's an OptoSensor unit in the door, and one of the two terminals connecting it looks like it's got hot - the white plastic cover has gone brown. This may or may not be related obviously.
Thanks in advance.

Hello there,

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Please note, I am just a moderator for this category, I can only try and find experts to help, I can't answer the question itself.

Thank you!


Customer: replied 3 years ago.

Yes, please try and find an answer. Thanks.


We will continue to look for a Professional to assist you.

Thank you for your patience,


Welcome, my name is ***** ***** I will be helping you with your problem today. If anything isn't clear, please just ask me.

Im so sorry that no one else has responded to you.

Apologies for my delay in replying, I only just came online and saw your question. Are you still looking for help with this?

Please don't rate my answer until we have explored all possible avenues. Please just use the reply button to contact me.

The first thing I would check is the heater itself
on this machine its a fairly complex through flow heater in the base
please go here you will see the heater
Click on the first picture, you will see the element tags sticking out to the right
Test for continuity here

Let me know what you find

Rob, Home Appliance Technician
Category: Appliance
Satisfied Customers: 6991
Experience: 20 yrs. experience with a major worldwide manufacturer.
Rob and other Appliance Specialists are ready to help you
Customer: replied 3 years ago.

Great, thanks for replying.

Is it possible to test continuity from inside the front door? There are a bunch of wires coming up from the bottom - do you know if there are two that are attached to these terminals?

I already have access inside the door, but there's a bit more work to get inside the base. Does it need to be pulled right out and tipped over to get access to the heater?


Personally I would want to test the heater itself, tracing back wiring can lead to all kinds of other issues, sorry.

For access, you need to remove the lower kick panle. If you still cant get to it, you have to take off the lid then the sides.
Oh the joy of appliance repairs !!

Dont forget to remove the wiring from one side of the element so as not to get a false reading

Customer: replied 3 years ago.

Great - I'll have a look in the next few days, as soon as I get the chance.

For some reason I've just received the following email from JustAnswer:

We're very sorry you're unhappy with the answer you received to your Appliance question from Rob on JustAnswer. We noticed that you did not rate your service and instead, you requested and received a refund.

I just wanted to let you know that I have not requested a refund, so there is something wrong with your system. I've done nothing, and was just waiting until I get the time to look at it properly.

Thanks for letting me know about the message.
Ill get it checked.

Just let me know about the dishwasher when you can, thats fine

Customer: replied 3 years ago.

Thanks for your patience. I finally got the time to throw myself on the kitchen floor.

Crikey, access is crazy on this thing. I had to take the right-side panel off, and could just get a screwdriver in to prise off one terminal from the heater. Then measured it and it was 24 Ohms, across the two big terminals that stick out of the white bit. Does this mean the heater's OK?

I also took out the Power Module PCB, as that was in front of me. I've attached some photos of one of the relays. Would you agree that the relay has got very hot and cooked its own solder joint?

The white connector below it in the photo is where the thick wires connect, so I'm guessing that it's very likely this is for the heater.

This PCB is about £140, so I'm going to try replacing the relay itself. I could possibly make it work by just resoldering the joint, but I want it to last. I'll see if I can get a higher-rated one that hopefully won't be getting as hot.

I'd be grateful if you could confirm that the heater resistance sounds right, and that I'm heading in a sensible direction.

Thank you very much.


Agree completely

The heater sounds about right, and the heater relay looks cooked.

If you are able to replace the relay, all should be good.

You might want to try just resoldering the joint and seeing for sure that this is the issue.
Youve then got time to replace the relay

Oh, and your right about the access, the joys of domestic appliances these days !!

Can I ask you to take a moment and rate my responses so far? Please use the smiley faces which you should now see. Please remember you are rating me personally, not the website or the problems you have had with this machine.
This will not close your question and you can still come back to me if you need more help

Customer: replied 3 years ago.

Great, I'll give that a go and see what happens. I've found a near-equivalent relay on ebay for a huge £3.52 including delivery (item 271177873177), so hopefully this job isn't going to be as bad for the wallet as I feared.

It's indentical ratings but is SPDT instead of SPST, but the NO pin is in the right place, so after snipping off the NC leg it should fit.

I'll click the "big grin" thing as soon as it's working. I'm very grateful for the pointers, as I didn't have a clue where to start really.


Sounds like a plan!!

Well done, and thanks in advance for the ratimg as its the only way I get credit for helping you with this

All the best

Customer: replied 3 years ago.

Hello. I'm still waiting for the relay to be delivered, after the ebay seller managed to send me a 12V version instead of the 9V one ordered.

Looking at it and thinking some more about it, I don't think the relay is actually the problem - I think the PCB track is too thin for the current, so the track has acted like a 9A fuse and has popped, right at the narrowest point where the pad meets the track.

I'm still going to replace the relay anyway, but will scrape off all the track coating and overlay it with soldered on copper wire all the way from the relay to the heater connector.

Hopefully it will be sorted within a week - the house is full of dishwasher parts at the moment, so I can't wait to fix it.