Ariston AWD12 – not filling

[andywash]

Hi,
When I set a programme, the red light comes on steady, the door locks and then nothing ie it doesn’t fill.
On further investigation, non of the water valves are being actuated by the programmer PCB .

I have completely reversed engineered the PCB schematics, and the wiring of the machine (Electrical/Electronic Engineer). I have checked the programmer for incorrect/correct voltages etc and eveything looks correct. I have checked all connections to controls/sensors etc and so no broken connections. I have checked the pressure switch operates and switches. Door interlock signal is working correctly.

My issue is that it looks like the programmer, is waiting on a specific signal, but not knowing what the programmer is looking for before it will start to fill (energise the water valves), then I am now a bit lost.
So a few questions:
1) Does anyone know, what the conditions are to fill from empty?
2) I have read replacing the motor brushes may fix this. Can anyone explain why this is the case, since to fill doesn’t involve the motor??
3) What is the operation of the pressure switch. I have assumed that one set of contacts is low pressure (ie empty) and the other set is high pressure (ie full). When in the above fault I fool the programmer into thinking that it is full, it turns on the water pump ( ie blow into the pressure switch). This does not seem correct to me that it would start to empty when the pressure goes high, when I would expect it to just continue the programme, unless my idea of operation of the pressure is wrong???

Wow!!….sorry the message is long, but I am determined to get this 8 yr old machine working again, as up and till now it has been completely faultless.

PS : The programmer electronics are very poor, not to surprising they fail often 😀

Thanks for any help
Andy

[andywash]

I have a feeling that the pressure switch is one level + overflow protection.
Does anyone know if the level contacts are normally closed or normally open, when there is no pressure

Thanks
Andy

[roly16]

Re: Ariston AWD12 – not filling

The water level contacts are normally open when the water level is low and closed when high. It could have a change-over switch which opens and closes. The pump – out when the switch is blown into will be you activating the overflow contacts.

Have you metered the inlet valve solenoid coils for continuity?

[andywash]

Re: Ariston AWD12 – not filling

Ok, managed to find the spec on the pressure switch and the contact arrangements. Its a simple changeover contact between low and high pressure. With an additional contact for overflow, which works at a slightly higher pressure. So the pressure switch is fine.

I have metered the valves, but I have traced the issue back to the programmer which is not even trying to energise the valve. Actually, I have traced it right back to the processor in the programmer.

So my question really is, what does the programmer need as inputs before it will energise the inlet water valve. I have checked the following and are ok:
1) Lo/Hi Pressure switch to programmer.
Now the programmer senses other items, but are any of these necessary before energising the valves
2) Motor Pin??
3) Drain Pump
4) Temp sensor dryer
5) Temp sensor drum
6) Motor tacho

Andy

[roly16]

Re: Ariston AWD12 – not filling

Possibly drain pump continuity; they rarely burn out but worth checking (ideally from the connector at the pcb ). Some of them are fitted with a toc in series with the winding to prevent burn-out when jammed.
To be on the safe side and to avoid mis-diagnosis it’s worth checking all the components.

[Penguin45]

Re: Ariston AWD12 – not filling

Just a point, Andy – the great majority of repairers don’t get down to board level repairs. If we identify a problem with the main pcb, we will replace, either with a new programmable board from The Indesit Company, or a reconditioned unit.

From a personal perspective, I’d check the row of light-duty triacs……..

Please post up your findings – we’ve had some interesting posts with regards to relays and burn-out resistors. It all adds to the knowledge pool.

Good luck,

Penguin45,
Moderator.

[Simon46]

Re: Ariston AWD12 – not filling

Or the motor brushes. Door locks, no action.

S.

[andywash]

Re: Ariston AWD12 – not filling

Penguin45 :
My initial thought was the triacs, which when I measured the voltages driving them I noticed that the triacs were not turning on. So I replaced them, but no change still not working. However, this was a mistake on my part in that the driving voltages were in the opposite sense, so the microprocessor wasn’t even turning them on. This lead me to look else where as to why the processor wasn’t turning them on ie its waiting for some other input condition.

Roly16:
The pump is fully operational, as when I cause the pressure switch to go to its flood level, the pump operates. Although, this operates from the pressure switch directly, I have also managed to operate it from the relay on the pcb, by forcing the driving logic to turn on the relay. Don’t worry I have been an electronic engineer for 20 yrs, so I know what I am doing.

Simon46:
You mention the motor bushes, but is it a requirement for it to fill with water. I can see that there is no reason for filling if the motor doesn’t have any continuity (ie bushes worn and not making contact with the commutator), but is this actually a condition that is checked by the programmer.

The pcb has been checked as far as I can, all diodes, transistors, triacs, relays all operate. So is it the motor brushes???
Also, the pcb over drives the relays, may be why there are some dead ones out there. The psu on the pcb is unregulated, basic design and cheap in my opinion.

So, is it the brushes???

Andy

[Simon46]

Re: Ariston AWD12 – not filling

Meter thru brushes across armature power off of course. Or just remove and inspect length.

S.

[andywash]

Re: Ariston AWD12 – not filling

Simon46:
The brushes are low and will do with replacing, but is this the cause of the non-filling problem. Unfortunately, I didn’t get to meter them before removing them, but now they are replaced it meters ok.

So, I placed it on a spin cycle and the motor turned as expected. Then I placed it on a wash cycle, and yes the valves were energised, so problem fixed!!!

Or, in the process of doing all this investigation have I fixed it by moving things ie loose connection or something or is it purely down to the brushes.

Essentially, I need to know if worn brushes will stop it from filling? Is this a known problem?
Also, for me why doesn’t it fill because the brushes are worn. Is it because there is no point in filling if the motor can’t turn?
That leads me on to another question, why does it just sit there and not show a fault. Its not as if the motor will fix its own brushes 😀
Thanks
Andy

[roly16]

Re: Ariston AWD12 – not filling

andywash wrote:
So, I placed it on a spin cycle and the motor turned as expected. Then I placed it on a wash cycle, and yes the valves were energised, so problem fixed!!!

Or, in the process of doing all this investigation have I fixed it by moving things ie loose connection

Posibly; possibly not. See below.

andywash wrote:
Essentially, I need to know if worn brushes will stop it from filling? Is this a known problem?

Easy to find out. Pull a wire off one of the brushes and see if it still fills. If it doesn’t, put the wire back on and see what happens. Your questions are then answered.

andywash wrote:
Also, for me why doesn’t it fill because the brushes are worn. Is it because there is no point in filling if the motor can’t turn?

If that’s the case possibly, or perhaps it’s designed not to fill if the processor picks up an open circuit on any of the components.

andywash wrote:
That leads me on to another question, why does it just sit there and not show a fault. Its not as if the motor will fix its own brushes 😀

Theoretically it probably should. The problem with all these micro-controlled machines is that you never really know how they’re going to behave when there’s a fault. In the old days if a machine didn’t fill you checked the circuits to the valves , pressure system (and drain pump as it was often connected in series with the valves) . If they were ok it had to be the [mechanical] programmer. Now, like with cars, any fault can show all sorts of odd symptoms. You can’t rely on an error code display happening; if it does that’s helpful, but you may have to physically check all the components.

[andywash]

Re: Ariston AWD12 – not filling

Easy to find out. Pull a wire off one of the brushes and see if it still fills. If it doesn’t, put the wire back on and see what happens. Your questions are then answered.

Now why didn’t I think of that. :rolls:

I will give it a go and let you know……oh hum, pull the machine out again, disconnect hoses/drain…fun fun fun!!

Anyway, thanks for the help.
Andy

[roly16]

Re: Ariston AWD12 – not filling

andywash wrote:

I will give it a go and let you know……oh hum, pull the machine out again, disconnect hoses/drain…fun fun fun!!

Anyway, thanks for the help.
Andy

Now you know what it’s like for us every day of the week 😥

[Simon46]

Re: Ariston AWD12 – not filling

It should have shown FO2 (two flashes) as brushes were failing on spin/ wash and dial clicking round. when no contact any more machine does not start.

S.

[andywash]

Re: Ariston AWD12 – not filling

Simon46:
Thanks for the info, thats reassuring to know it won’t start when the brushes go completely open. I will order some and then try disconnecting them to see if it produces the same fault, no point in dragging out the old lump more than once. I shouldn’t say that really its being working for 8 yrs now and used every single day.

roly16:
I can sympathise, but for me if its anything involved with electronics then the whole family and friends will always ask me to fix it and I don’t get paid for it. At least its not my day job. 😕

Next job Mums dish washer, built-in and its sprung a leak. Looks to be between the motor/empellor of the pump. 🙁 Time for some searching the forums

Anyway, thanks again everyone, will let you know the final outcome.
Cheers
Andy

[Author]

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