bosch Bosch Vario Perfect waq284d0gb Tripping

[pat]

I have a bosch Vario Perfect waq284d0gb, it has been working perfectly for about four years but has now started tripping the mains RCD. It doesn't trip as soon as it is plugged in but when the programmer is moved it trips immediately. At first I thought it was the mains filter so i replaced that. It worked perfectly for two days but now it is back to tripping the mains RCD again. The wiring looks in really good condition, no signs of water ingress, leaks or corrosion. I have tried plugging it into a different socket (& RCD) but i still have the same issue. I am thinking that it could be the encoder or a short on one of the boards. I am assuming that the water valve/pump, heater element and motor  won't have power until the program is started? Any help would be very much appreciated. 

 

[Whitegoodshelp (Andy)]

Hi. Do you mean when you manually turn the dial by hand or when it moves on during a wash cycle?

[pat]

Hi Andy, Sorry I should have been clearer, it is when i manually turn the programmer, as soon as i turn it in either direction it trips. 

 

Edited August 19, 2019 by pat

[Whitegoodshelp (Andy)]

I thought you meant that but just wanted to make sure. Is it a manual timer or does it operate an electronic display? If manual can you select the required wash cycle with washer turned off and then switch it on to see if the washer works ok?

I’m wondering if it’s sparking internally when turned and that’s tripping sensitive RCD. If it’s the latter it’s hard to imagine what would be causing it. You would need to put a special insulation test meter on the machine and turn the dial to see if anything shorts to earth. 

[pat]

It is all electronic, it has two circuit boards, one power board with mini transformers and a program board with a digital encoder on it. It doesn't matter which way i turn it it trips immediately.

[Whitegoodshelp (Andy)]

Unfortunately you need an insulation test meter to work out what’s causing it to trip. As you say when the dial is just turned you wouldn’t expect it to supply power to any parts until it’s actually started but it’s possible some switching is done on the neutral side and if a part is down-to-earth (or low insulation) it will trip as soon as power gets to it even if it’s not actually operating. 

If it was the mains filter you’d expect it to trip as soon as power is applied and washer is switched on. But if it worked ok for 2 days that’s strange. 

An engineer would put the insulation test meter on it to trace exactly what part of any is leaking to earth which is the main cause of tripping. Without being able to do that you are unable to rule out any of the several parts that could be causing it 

https://www.whitegoodshelp.co.uk/washing-machine-fusing-electrics/

[pat]

It is very strange, the encoder has a 240V feed and the circuit board around it  looks slightly discoloured so it is possible it is the encoder but I think it only acts as switch so it seems unlikely, as you say without diagnostics i won't be able to tell what the issue is. Thanks for your help 

[Whitegoodshelp (Andy)]

On washing machine PCBs there is usually some black sooty areas which are very often taken for burning but are often just where muck and dust has accumulated around a hot area such as a big resistor. So be aware of that. 

Also, washing machine engineers generally know very little about faults on pcbs as we are never expected to repair them. They have always been parts that are replaced for any fault and diagnosed by process of elimination. 

If you get the bottom of it please update us. Also, a possible option might be to get in touch with QER repairs who specialise in appliance pcbs. 

[pat]

Ok Just to rap this up, I sent both boards off to QER to be tested and repaired. They found an issue with one capacitor but this didn't fix the issue. No issues with QER except comms could be a bit better. They clearly know there stuff and i have no problem believing that the capacitor is out of whack after 4 or 5 years. So back to the drawing board for the fault. Next possible culprit was the heater element. This tested fine for resistance as did the temp sensor. I put a voltmeter across the main terminals and was surprised to see 55V as soon as the machine was turned on. So i disconnected the heater element and hey presto the RCD stopped tripping and i could run the machine. I don't have a megger so i can't really test for earth leaks etc. But i did connect the meter from the heater terminal and the heater earth to see if there was any spike when it tripped. It wasn't definitive as the meter doesn't react as fast as the RCD but there was definitely voltage indicating that the heater element was shorting so i ordered a heater element and temp sensor from Bosch (fantastic support from them by the way), the element arrived so i removed the old element only to find a complete mess of washing powder, fibres and limescale. New one fitted and surprise surprise it works! So the take away here is that the heater element (In this model at least) is powered as soon as the machine is turned on, possible as part of a test cycle

. So any issue with the element could potentially cause  a short. The other is that this horrid mess is from about four years of use (yes we do use a descaler periodically) so limescale and detritus can build up pretty quickly.

I hope this useful for others. 

Many thanks for the help Andy, it is very much appreciated.

Edited September 5, 2019 by pat

[Whitegoodshelp (Andy)]

Many thanks for the update. It shows that as I said without an insulation test meter you can’t properly troubleshoot a fusing or tripping washing machine. However, your element was in such a bad state it’s quite obvious it was at fault. 

Glad you sorted it. Your element should never get in that condition though. The main problem is likely to be not using enough detergent. You shouldn’t need anti limescale tablets although the won’t do any harm. 

Ensure you know exactly how hard your water is and carefully check the detergent packets to see how much detergent you need to use. You don’t want the new element going the same way.