FDM550 Dishwasher Intermittent Dry Cycle

[whitehse46@hotmail.com]

My dishwasher has developed a fault where it does not dry most of the time.
It has days were it is ok then doesn’t.
It always heats water and steams in the wash cycle so element must be good.
It then drains rinses with fresh cold but then doesn’t heat this.
Machine then just steps on to the end
Leaving dishes cold clean but wet

Any ideas I am an electrical engineer so happy to test etc could it be an intermittent temp sensor etc ideas and a steer………

Cheers guys

[whitehse46@hotmail.com]

Ok so I understand so much more already. When I run test mode I get alarm 1+3 which apparently says 2.5 litres of water added not detected. So I will try cleaning pipes and checking pressure switch. Any other suggestions or hints

[whitehse46@hotmail.com]

Pipe cleaned and pressure sensor changed oh no still intermittent

[electrofix]

assume your not using the fast wash as that has no drying phase

Dave

[whitehse46@hotmail.com]

No occurs on normal cycle. Happening about 1 in 3 washes. And sometimes fails on test. I will check output hose for syphoning next but unlikely. Then I will check connector on circuit board. Machine still washes which sort of is weird that it does a fill a rinse a fill and a wash and then fails on hot rinse and pumps out

[electrofix]

try opening the door after its filled and adding half a pan of water

see if it changes anything

Dave

[whitehse46@hotmail.com]

Ok so I’ve found out more after your idea. So in test the machine is supposed to put in 2.5 litres, and then check pressure sensor. But it’s short filling ie only putting in 1.7 litres. So fails. If I open the door and chuck a cheeky litre in to fox it its happy and runs. Hence fault is not pressure sensor it’s pointing more at impeller. Checked water inlet filter and tried reducing pressure at tap still short filling will look at replacing impeller next what you think….

[whitehse46@hotmail.com]

I said impeller I think it’s called turbine

[electrofix]

on a lot of later machines they use virtual sensors. They monitor the motor current and dependant on load they can check if there is enough water to turn on the heater

Dave

[whitehse46@hotmail.com]

I’ve just ordered an air brake and turbine…. Quite how it can be reading wrong I don’t know but worth a punt at 30 quid

[electrofix]

the air brake uses a reed switch. the reed switch closes as a magnet goes past it. over time the contact wont be 100 {e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} and faults happen.

Dave

[whitehse46@hotmail.com]

Ok so that hasent worked changed air brake. It’s still intermittent. Now it’s obviously thinking it’s seeing to many turbine pulses. So my guess its triggering on the positive and negative going edges. So my next visit edge connection on the controller. But it could be a fault in the 20ma loop etc . Starting to look like controller fault. Drat that’s an expensive game programmers cards and card can’t spend £180 on a 8 year old dishwasher. Perhaps a dry joint or capacitor. Worth a play here I go.

[whitehse46@hotmail.com]

So I’ve been barking up the wrong tree….retested amount of water pumping out was now 2 litres so went back to recheck pressure sensor and perhaps play with it as I have a spare pressure switch Removed tube again, I could blow but couldn’t suck. So cleaned out sump, full of crud…… this was intermittently blocking tube to switch, which actually operates well before 2 litre the test amount….bloody hell great wild goose chase for the obvious fault, well I have a lot of spare parts and a working dishwasher yipeeeee……. ( well foxed by when you added .5 litre it then worked ok)

So fault fixed food gunge in sump causing pressure sensor to behave intermittently

[Author]

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