Discuss Dishwasher Problem. What do you think? in the Electrical Appliances Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
52
Hi everyone

Commercial dishwasher stopped working. Water heats up but when the temperature reaches the right temperature the wash start button doesn't start the wash cycle. Checked everything out. Buttons, motors they all fine. Drain pump works but the behaviour is whacky. Normally you press the drain button and release it when you hear the drain pump kick in. The button powers a relay, the pump starts pumping, water drains, water pressure switch breaks circuit when the tank is empty and pump stops. Instead you press the drain button and the pump starts. You release the button and drain pump stops. You have to hold the drain button down to continue draining. Now here's the odd thing. As the tank drains with your thumb on the drain button it gets to a point, before the tank is empty, where the wash cycle begins and it does so even when the door is open ie: the door microswitch is being bypassed. I have a had a good look around for signs of short circuit but can't see anything. Opened up the loom. There's usually a bit of a clue if wiring looms are leaking. There is a relay contactor in the machine that sits between the timer and the various pumps. I am thinking the problem might be this contactor. What do you guys think?
 
Hi bud,details of make,model,any pics etc,will be requested,or it's all gonna be a stab in the dark.
It could be old enough,not to have a door switch,and detection of drum load could be down to blocked drain.....all happened before.:)
 
Hi bud,details of make,model,any pics etc,will be requested,or it's all gonna be a stab in the dark.
It could be old enough,not to have a door switch,and detection of drum load could be down to blocked drain.....all happened before.:)

Thanks for the response.

I didn't post any of that because these commercial dishwashers are generally the same from a functional perspective.

It's also a bit of a mash up in that it was bought 2nd hand and, on investigation, neither the parts nor the wiring are to spec as far as the manufacturer's manuals and wiring diagrams are concerned.

Not that it matters much because it has been working fine for four years. It just doesn't help a lot when trying to diagnose the problem.

Still, if it's any use to anyone it is a Prodis E80. I attach a picture of the washer.

The contactor is a Prodis T50 30525 30 amp. So if anyone know these to go bad let me know.

PRO30525 T50 CONTACTOR large ( 30amp ) - http://spares.prodis.co.uk/index.php/glass-dishwasher-spares/pro30525-t50-contactor-large-30amp.html

For clarification purposes, it is nothing to do with a blocked drain hose. I know this because the machine drains fine which it wouldn't do if the drain hose is blocked.

Also it doesn't have a drum because it's a dishwasher not a washing machine.

But everything works fine. All the motors including the timer unit. All tested in isolation.

Just out of sequence. That's the issue. The drain circuit shouldn't be active during the wash phase and vice versa.

That's why I think its the contactor. A short in the contactor could activate two relays instead of one. That would explain how these two phases might occur simultaneously.

Dishwasher Problem. What do you think? IMG_20180710_150344 - EletriciansForums.net
 
Hi,bud,had a quick trawl of unit (after me accusing it of having a drum:))
Does it have a motor driven controller? I know they work on short cycles,but is the cycle controlled by an electronic device,or has it an old-school cam/contactor phase controller?

They are relatively simple,in terms of operation,but the door switch not functioning needs attending to.
 
Hi,bud,had a quick trawl of unit (after me accusing it of having a drum:))
Does it have a motor driven controller? I know they work on short cycles,but is the cycle controlled by an electronic device,or has it an old-school cam/contactor phase controller?

They are relatively simple,in terms of operation,but the door switch not functioning needs attending to.

Door micro is fine and functional. They tend to fail safe in any case.
It is being bypassed. It has a five cam timer. The cams are not free to move independently. I have checked that thoroughly. Literally watched it go round through the wash cycle. The filling, heating and wash cycle is fine. Plus the contactor as described. There's no electronic control board. The wiring diagrams are very crude and not much use to be honest. Also in Spanish. It's a 2 minute wash cycle. It's this odd behaviour of the draining process that's the issue. The drain doesn't use the timer. I say that because the timer doesn't move when draining. The only shared component between the wash and drain cycles is the contactor. That's why I think it's the problem.

Dishwasher Problem. What do you think? cra - EletriciansForums.net

Dishwasher Problem. What do you think? IMG_20190127_125322 - EletriciansForums.net
 
Hi - I'm not experienced with this machine - but here's a few Sunday morning thoughts :) .
The circuit diagram green section has the drain push button (scario) and there is a feed back connection after the button is pressed and the contactor closes (at 38). This keeps the drain pump (pompa scar.) on till the circuit is interrupted by the pressure release switch (pressostato at top right of diagram near 3, 8, 81), as you've described used to happen. So that "latching" circuit is not working and that could be the contactor or a connection to it.
The door switch (finecorsa porta 4, 41) is on the bottom of the drawing and if the door is open the main pumps in the DW should be off...
 
Hi - I'm not experienced with this machine - but here's a few Sunday morning thoughts :) .
The circuit diagram green section has the drain push button (scario) and there is a feed back connection after the button is pressed and the contactor closes (at 38). This keeps the drain pump (pompa scar.) on till the circuit is interrupted by the pressure release switch (pressostato at top right of diagram near 3, 8, 81), as you've described used to happen. So that "latching" circuit is not working and that could be the contactor or a connection to it.
The door switch (finecorsa porta 4, 41) is on the bottom of the drawing and if the door is open the main pumps in the DW should be off...

That's my interpretation of what's going on. I haven't actually removed the contactor yet because it is at the back behind other stuff and there's no rear access. The next step is to remove it and test it. It's a small yet busy kitchen and I take up a lot of floor space when I'm lying down.
 
The yellow disc on that controller looks a bit dodgy.

It looks a bit gnarly but that's the rinse aid pump cam and that's working fine. Looks like it has jammed up at some point in its life and would probably be a good idea to replace it. But it costs £180 so if it's working that'll do for another day. The contactor s £110. I think that's my priority at the moment.
 
Hi,is the drain pumped or gravity (it's an option)
I would be tempted to mark up the cam switch terminals,and leave the motor connected,whilst the switching is checked,to iron out any seized or non-functioning contacts.
These things are always a pain,but just replacing single components,is not always a cheap method,as they know how to charge...

At least you only have to wait through a short cycle :)
 
Hi,is the drain pumped or gravity (it's an option)
I would be tempted to mark up the cam switch terminals,and leave the motor connected,whilst the switching is checked,to iron out any seized or non-functioning contacts.
These things are always a pain,but just replacing single components,is not always a cheap method,as they know how to charge...

At least you only have to wait through a short cycle :)


It's pumped. The parts are are pricy. OTT in my opinion. If we were talking £25 or so for this contactor I would just buy one and swap it out. But at £110 you have to be more cautious because they don't take them back if you get it wrong. I have decided I will have to remove the contactor and see if I can test it.
 
If you are going to get involved,this would be the best move,i reckon.

Check the terminal numbers and configuration,of the controller,and just check the N/O and N/C operation.

In the past,i have rigged a simple pair of lamps (larger watts the better) and popped a 3A fuse in the test supply (C) just to watch what and when the lamps perform.
You would do this,on each of the 5 cam switches,but the short cycle,makes this easy enough. I would urge,not to remove the drive motor,and manually operate the cams,to speed the job up. I have had previously faulty contacts,decide to function,when whipped through their cycle,at an increased speed.:)

Perseverance,is the key....even if it feels,you are doing it solely for the craic;)
 
If you are going to get involved,this would be the best move,i reckon.

Check the terminal numbers and configuration,of the controller,and just check the N/O and N/C operation.

In the past,i have rigged a simple pair of lamps (larger watts the better) and popped a 3A fuse in the test supply (C) just to watch what and when the lamps perform.
You would do this,on each of the 5 cam switches,but the short cycle,makes this easy enough. I would urge,not to remove the drive motor,and manually operate the cams,to speed the job up. I have had previously faulty contacts,decide to function,when whipped through their cycle,at an increased speed.:)

Perseverance,is the key....even if it feels,you are doing it solely for the craic;)

Test the contactor. That's the plan. The drain process, which is wher the problem lies, doesn't use the timer so I will focus on the drain process. I will be looking for a way I can energise the wash cycle relay via the drain relay. I just wish the wiring diagrams weren't so primitive. When I get it out there may be evidence of damage. I had an endoscope in there and there is some brown marking on the contactor casing. Maybe it has gotten wet and shorted out. We shall see.
 

Reply to Dishwasher Problem. What do you think? in the Electrical Appliances Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock