Ariston AFA250 fault

[aneng]

Hi,

I’ve managed to keep my ancient (well, 12yr old!) Ariston AFA250 going over the years – it’s almost become a mission to never let it die 🙂 It’s had allsorts in its time – pump housings, spraybars, filters, seals, door switches etc, but this time it has me stumped.

For some time now it has been intermittently ending the cycle early with the last of the four LEDs flashing fast, and the dishes mostly clean, but not dry, though the cutlery often has a white powdery film in places when it does this.

According to error code guides I’ve managed to find, #4 LED flashing fast means some sort of timeout on the temperature – i.e. the controller thinks it’s not getting hot enough, or it really isn’t getting hot enough. I’ve cleaned up all the controller PCB connections and resoldered the thermistor leads. I also filled the little thermistor carrier with heatsink paste and also put paste between the door panel and the thermistor carrier, but all to no avail.

I get a better chance of a completed wash if I choose the intensive cycle (70C) instead of the normal (55C) one, suggesting that temperature may well be an issue.

I’ve looked at the thermistor itself under a microscope (it’s a tiny SMD device) and there are no markings at all to help me identify it for a substitute part.

I’m loathe to shell out for a complete replacement controller (if I can even get one) if it’s just a 50p thermistor.

Any suggestions folks ?

Many thanks,

Kev.

[iadom]

Re: Ariston AFA250 fault

Not heard of anyone sourcing the thermistor for this pcb, fault could also be caused by the heater relay on the board breaking down under load.

[electrofix]

Re: Ariston AFA250 fault

does it heat at all or does it just stay cold ?

Dave

[aneng]

Re: Ariston AFA250 fault

It heats. I’ve stuck a thermometer in there and it gets to about 48C on the 55C cycle. I’ve not checked it on the 70C cycle.

[electrofix]

Re: Ariston AFA250 fault

well it cant be a thermistor problem on those readings, granted its a bit low but its only a little over 10{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d}

Dave

[aneng]

Re: Ariston AFA250 fault

Hmmm… I’ll stick my ‘scope on the relay output during a cycle and see if that’s flaky. I can’t imagine it’s the microprocessor. I’ll test the thermistor too – you never know, it might be intermittent… unlikely, but….

[aneng]

Re: Ariston AFA250 fault

This is bugging me now… I found the test program instructions here : http://www.selfix-uk.co.uk/Test{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d}20progr … FA2505.htm and discovered that then selecting the short test (position 1), it runs the long test (which is supposed to run at position 2) and selecting the long test (postition 2), the lights just go out and it does nothing.

However, it completes the long test as detailed and returns no errors. The water heats up to 55C – everything works. Yet, when I run it on a normal cycle, it intermittently aborts with a S0001 error – which according to everything is supposed to be a ‘not heating up in the required time’ (or words to that effect).

I tested the thermistor and that seems ok – or at least the resistance changes with temperature. I’ve checked the supply to the heater and the heater resistance – that’s all ok too.

I’m stumped.

The only thing I’ve got that’s not normal is the test programme running the wrong test on position 1 and nothing on position 2. There is a seller on eBay offering a repair service for the controller for £34, but I’m not even sure if the controller is at fault.

[electrofix]

Re: Ariston AFA250 fault

if its QER they are ok if its not would not trust them

dave

[aneng]

Re: Ariston AFA250 fault

It is indeed QER. The question is though, does this look like a controller fault ?

[aneng]

Re: Ariston AFA250 fault

On a whim, I decided to replace the relay – as @iadom suggested.

So far – it’s working perfectly! I monitored the temp on a regular wash and for the first time, discovered it does a hot pre-rinse ! Thanks iadom – it looks like my 14 year old machine lives on !!!!

[aneng]

Re: Ariston AFA250 fault

Update: F**@;:&*&*!!!!!! It’s back to playing up again.

I have a digital thermometer probe in there, monitoring the water temp, and on a normal (55C) cycle, it got up to 40C and stopped heating any further. Without resetting it, I popped the front panel off and stuck the thermistor against a freezer block, thinking that if it was the thermistor wrongly telling the controller that the correct temp had been reached, it would hopefully make the heater come back on if I cooled it. The heater remained off.

Next, I popped the PCB out of the carrier (very carefully, as it was all still live) and tested the voltage going to the relay coil – nothing. So, for whatever reason, the controller isn’t switching the relay on correctly / for long enough.

Next up, I soldered two wires to the relay coil contacts and clipped them to my meter, reassembled the PCB carrier and set it off in test mode (as per my previous posts) – exactly on cue, the relay coil voltage came up to 10VDC, the relay activated and the heater came on. It heated the water to just shy of 60C and completed the test cycle without any errors. Bloody thing !!!

It’s beginning to look more like a controller fault – with the strange caveat that it’s running fine on a test cycle.

[aneng]

Re: Ariston AFA250 fault

Update: It would appear it was the thermistor all along. I emailed QER to ask if they thought they might be able to repair my controller and they replied that it sounded like the thermistor and that it should measure about 18K Ohms, and if that was ok, they would see what they could do with the board. I measured my thermistor and it was 58K, so I got a replacement from Maplins – but the closest they had was 15K. I soldered it in to the sensor housing and tried a test wash – it got to 40 C and completed successfully. I then added a couple of resistors in series to bring the starting resistance up to 18K and ran another test wash – which gave me 50 C, so I knew I was on the right track. After adding another 1.5K resistor, the next wash reached the magic 55C.

Total cost: 49 pence.

[aneng]

Re: Ariston AFA250 fault

Could someone offer any advice on washing cycles please ? According to my user manual, a ‘Normal’ cycle is supposed to consist of:

• 2 pre-washes with cold water[/*:m:2xag5l00]
• Extended wash at 55°C[/*:m:2xag5l00]
• Rinse with hot water at 70°C[/*:m:2xag5l00]
• Drying.[/*:m:2xag5l00]

What is actually happening is this:

• 2 pre-washes with cold water (30min & 10min)[/*:m:2xag5l00]
• Cold wash (35min, detergent releases 3min in)[/*:m:2xag5l00]
• Rinse with hot water at 55°C (20min, heating starts after 5min)[/*:m:2xag5l00]
• Drying[/*:m:2xag5l00]

I’m puzzled why the wash (with detergent) is cold, though I did read somewhere that most dishwasher wash cycles are cold. Is that true ? What do you think is going on here ? Is the manual wrong or has the controller lost its marbles ?

Incidentally, does anyone know what that PCB mounted pushbutton is for on the back of the BIT100 controller ?

Many thanks!

[Author]

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