Bosch serie 6 washer dryer skips to drain only

[Jan77]

Hi all,

I bought this very cheap nearly brand new but faulty Bosch Serie 6 washer dryer WVG30461GB / 01. I bought it with a risk I might not be able to fix it but then at least I will learn something new and will put my brain on the spin.

 It seems to me like the PCB is faulty as any program selection goes to a drain cycle after few seconds after relays tried to set and feedback received . Any selection on front display is rejected with double beep. Drain cycle starts itself automatically. Drying programs are the same, going to the drain cycle after few seconds. When the draining is finished it freeze showing the full time duration of particular program on display. Door lock is constantly locked.

 I know this is a tough one to ask for any clue, but if there is anyone who would be able to point me in good direction I would appreciate that very much.

 

Happy day to all!

 

Jan 

[Whitegoodshelp (Andy)]

Hello Jan. Yes it's a tough one because the symptoms are all over the place. I wouldn't risk buying a new pcb, they are too expensive and there's no guarantee it is the fault or the only fault. You could try sending it to QER repairs though. They should have a testing service and reconditioned pcbs. They specialise in washing machine pcbs.

[Jan77]

Hello Andy, thank you for giving a thought to my issues with the washer and your advice on pcb. I had the pcb out for visual check and didn't notice anything wrong on the board, the control front panel board is also without any noticeable damage.I pulled and reconnected all connectors in case of some oxidation build up. I will yet make a visual check of the motor module and will run tests on all sensors, solenoids, pressure switch, etc. before deciding to send the pcb for test. The machine stood in showcase property for 2 years and apparently stopped working after few washes when someone moved in. Do you think that the solenoids could seize or something if they not acted for so long being plumbed in ? They are closed not opening, but as I said i must yet check if they get the impulse to open. Many thanks. 

[Jan77]

Another observation is that the machine starts draining even with the door open. It signals the door is open but however begins to drain. Could this suggest anything in the loop? Perhaps the pressure sensor? 

[Jan77]

I have had the pressure sensor out and did some measuring whilst blowing into the pressure pipe and I'm getting constant voltage on all 3 ports of the sensor. No voltage fluctuation whatsoever. Does this suggest that the sensor could be faulty?

[Whitegoodshelp (Andy)]

Did you blow down the pressure pipe the other way? Into the tub? A blockage at the other end can cause problems for sure. It can cause the washing machine to overfill. If a washing machine thinks it is overfilling, it will commonly energise the pump constantly trying to get rid of the excess water. It will keep the pump running until it receives the signal that the water has been pumped away. However, a fault in the pressure system, or a blockage in the pressure system can prevent that signal from ever occurring.

Having said that, if there was a blocked pressure system then as soon as you remove the pressure tubing from the pressure switch the air pressure would be released and the pressure switch should switch off. This should stop the problems, at least until more water got into the washing in and caused the problem again.

Another fault that can trigger the pump to be running constantly on some washing machines is believe it or not earth faults. If there is an earth fault on some washing machines they can behave bizarrely. So make sure that the washing machine is properly earthed. But more importantly you would really need to check that no parts on the washing machine have low insulation readings. This would require using a specialist meter though that tests with 500 V DC. 

Also it is common for faulty PCBs to show no visible problems. They can of course have dry joints, or blown parts, but many component failures will not have visible signs. So the lack of any signs doesn't prove anything when it comes to diagnosis. 

[Jan77]

Hi Andy, 

thank you for for your further thoughts and suggestions.

I did blown the tube the other way into the tub as well and was fine, no resistance at all and I could hear the 'sound' of my breath entering the tub. I have also tried to start a program with the tube from pressure switch disconnected which has not made any difference to the behavior I described above. 

As time will permits (busy week ahead) I will check the machine is earthed well and will also try to get more readings from the components. Shall I ask you if the heating element should start heating as soon as the wash program is started or only after the water in the drum is filled to satisfactory level? I need to return to this and do more measuring but I think I had a live on heating element whilst the draining pump was active but didn't sense any heat in the drum. 

 

This all IS so confusing, I will begin a thorough analysis of each section of the machine so hopefully to be able to get more clues.

 

Thank you again.

Jan

 

[Whitegoodshelp (Andy)]

The heater should come in when correct level of water is inside. It’s possible for some parts to have a live supply but if there’s no neutral return it won’t operate. Some machines in the past have had all components switched on and off on the neutral side, with all parts in machine live all the time. 

It’s possible it shouldn’t be live though. 

Check out my site Whitegoodshelp and search for how pressure system works for an idea about pressure system.  

[Jan77]

Understood about the neutral return, thank you. I will check your site, I very much appreciate your help.

 

[Jan77]

I was able to work on the machine again last night and I think I have a breakthrough discovery on the problem.

By coincidence I figured out that I'm able to start the selected program. I can start the program in first 2 seconds when it lights up on the display, after 2 seconds the machine aborts the program and begins its safety mode of draining water. When I select the drying program then in those 2 seconds I get about 1 revolution of the drum and a program status light comes on until aborted. There is less to observe when washing program selected as those begin with water being filled, but again in the 2 seconds span I have program status light coming up. When a rinse program selected I get correct rinse status light on. Also in those 2 seconds I'm able to make adjustments to the program (temperature, spin rpm, delayed start..) . Door lock is constantly closed. This led me to think that the PCB might not be at fault.  

I have measured the returns from the pressure sensor on the ports at PCB whilst blowing in the pressure tube and I get constant readings at all 3 ports regardless the pressure created. I sense that when I blow in there is very little travel enabled as opposed when I suck the air away the magnet (or what is inside that coil) moves lot more. 

For this day I'm drawing a conclusion that the pressure sensor is at fault being stuck and sending incorrect constant information that the machine is filled with water.

I will order a new pressure sensor on Monday and will see if that will clear the fault.

 

 

[Whitegoodshelp (Andy)]

Pressure switch should normally be off or on. Historically they’ve just been off until the correct amount of water creates enough pressure to switch the pressure switch on. The latest type of pressure switch seems to have a magnet inside a coil so potentially they might detect proper levels.

If a pressure system is telling a washing machine it has water in when it hasn’t it usually tries to wash and rinse with no water in the drum. But modern washing machines operate the pump for 30 seconds before filling to wash.  So it’s possible they check to make sure there’s no water in before filling. But I would still expect it to try draining the water out for a few minutes before giving up.

If the pressure system is saying it has water in when it hasn’t I would still expect it to work on a spin only cycle. I’d expect it to try to drain water out for 2 or 3 minutes waiting for the signal that the water has gone. When it doesn’t get the signal it should then abort without spinning.

If the washer thinks it’s overfilled though it should keep pumping trying to get rid of the water. But again I would expect it to try for several minutes at least. If the pressure switch isn’t expensive it might be worth a try but not sure. Fingers crossed. 

[Jan77]

Hi Andy,

this is the machine with the latest analogue pressure sensor with the magnet inside the coil.

The machine does its check when plugged in mains (electricity) and when selection of a program is made and  I think sets itself to a safety mode upon receiving this incorrect feedback. It also never release the latch on the lock so the door remain locked at all times. 

The discovery is that I think that there are 2 seconds delay before the PCB locks the display front panel after the program selection is made and if I press START the program immediately after it is made available on the display the program then starts and runs for 2-3 seconds and is aborted with the drain pump coming on (the display and controls then become locked) keeping draining for 3-4 minutes and then stops as I think is programmed for safety mode so that with the valves shut the drum should be emptied in that time. It is very much possible that the programs begin with short draining.

 I think that the voltage return from the pressure switch should fluctuate between 5 - 10 V and I'm reading constant 9.4 V, it sort of explains the symptoms for me at this moment.

The sensor is £40 from Bosch , but I found exactly the same at  ApplianceSparesWarehouse for £18 so I will give it a go to replace it and see if it would fix the error.

Many thanks again for your thoughts and information on the subject as it directs me towards understanding the logic of the machine's behavior.

 

 

[Whitegoodshelp (Andy)]

Let me know what happens whether it fixes it or not. 

[Jan77]

I will, definitely. I should have the part on Tuesday.

[Whitegoodshelp (Andy)]

Fingers crossed. It is difficult to imagine what might go wrong with a modern pressure switch. The pressure switch has always been one of the most reliable parts in a washing machine. However, they are now a very different design to what they have historically been for probably over 50 years. As far as I'm aware they have a magnet that presumably gets raised up and down by air pressure inside the coil. An extremely simple device.  The only thing that I would expect to go wrong with one is if by any chance the coil goes open circuit. I can't imagine anything going wrong with the magnet. Of course other issues such as a blocked pressure system, or an air leak can cause problems with the pressure switch function. If you still have problems by the chance make sure you check the continuity of connections from all of the pressure switch wires right back to where they connect to other parts in the machine if you haven't already.

[Whitegoodshelp (Andy)]

Just a few extra thoughts just in case they are helpful. According to the error information I have on Bosch washing machines (which is far from up-to-date) there should allow about 6 minutes to drain, and also about 6 minutes to fill. So if there is an error where the washing machine doesn't detect it has taken the correct amount of water in, or doesn't detect that it has pumped the waterway successfully it should have tried to do so for around 6 minutes before aborting. Also most faults should produce some sort of an error code.

There should normally also attempt to start the motor 8 times before advancing to the off position. Have you checked the carbon brushes just in case? Most faults should occur after several minutes the absolute minimum. So if the washing machine thinks it is full of water and you put it on a spin cycle it should try to pump the water out for about 6 minutes before aborting. 

[Jan77]

If it proves to be it I will dissect the faulty sensor to see what it looks like inside. I got the sense like if it was seized in its upper part (higher pressure). For now I'm sticking with the fact that it does send constant reading to the PCB ( when i created different pressure conditions by blowing in tube) and now when discovered that the front panel communicates the symptoms encouraged me to replace it and see. I mentioned on my first entry that the machine is 2-3 years old but only done 2-3 washes so it is like brand new and clean quite pleasure to work on. I believe the motor on this machine is brush-less, having some magnets instead.

Until tomorrow when I will replace the sensor I'd like to think that it will be sorted then will push further with it if not.

[Whitegoodshelp (Andy)]

I am wondering if maybe the difference in resistance readings or voltage readings in the coil are likely to be so small, with such a small magnet, and such relatively small movements that it is only readable accurately by the PCB itself.

[Jan77]

Sadly, have to report that the fault persists after replacing the sensor, so as time will permit I will be trying to crack it. Will do basic checks of wire continuity around the sensor and door lock and if nothing will probably send the PCB for a test. Damn

[Whitegoodshelp (Andy)]

Thanks for the update. I would have been surprised but pleased for you if it had worked. If you still suspect the PCB you could still try contacting QER. Have you tried checking parts individually with continuity test meter as some parts can cause weird faults if they are open circuit. Thinking of the heating element, motor etc. Any faults are supposed to be captured by the software and produce an error code. So faults that don't produce an error code are often very difficult to diagnose.

[Jan77]

Hi Andy,

this morning I came across you tube video on how to read an error code and I tried it and it worked. I got E26 error code on the display which corresponds with faulty pressure sensor. Now I don't know if I need to clear that error somehow or if the problem persists and I should rather concentrate on measuring continuity of wires and maybe track a path on PCB. I'm going away for a week tomorrow so I won't be able to do more tests until back.

I have also posted few short videos on you tube of the behavior of front panel display and starting the programs works right now. If you interested to see it I have attached the links:

 

Ups, can't post with you tube link.

 

 

[Whitegoodshelp (Andy)]

Any time a fault is fixed, the error should reset. It may be retained in a memory accessible via special methods but it should stop being displayed to a customer. Try just linking to the videos?

[Jan77]

https://www.youtube.com/watch?v=4FXyDoYlq_0

https://www.youtube.com/watch?v=emvXHrncefA

https://www.youtube.com/watch?v=A2NsN0e9qBY

https://www.youtube.com/watch?v=DFvjI8FOdo0

 

Managed to post the links to the videos. I will take a video of the error code and post later.

 

I was away few days so haven't done anything on the machine since last week. If  I recap the situation :

- error code E26 , analog pressure sensor faulty ( now replaced)

- there are 3 wires to the pressure sensor and the pressure tube, 

- I have physically checked for tube blockage 

- I will check the continuity  and for possible short circuit of the wires, I think I have already done that before but to be 100% sure I'll do it again

 

If the wires are fine I understand that the problem would be on PCB , what do you think Andy?

[Jan77]

Here is the video of error code reading

https://www.youtube.com/watch?v=_O_ana9pxAY

 

[Whitegoodshelp (Andy)]

Hello there. I'm not understanding why you keep pressing the start stop, pause button and all the other buttons? What happens when you put it on a non-fast coloureds cottons wash, then switch it on and leave it? Washing machine should normally engage the pump and then after up to 30 seconds it should start taking in some water. But the videos you have put up are puzzling to me because you just keep pressing lots of buttons and getting beeps?