AEG Favorit F55010 VI not heating up

[fixitall]

Hi all,

I need some help with this one.

Some weeks ago I noticed the washing performance of my dishwasher got really bad. Especially on plastic pieces a thin film of a greasy substance remained after the program finished.

I did the obvious: clean the filters, checked the salt, other liquids.
The performance did not improve.

Then I started to suspect the temperature.
I stopped the programs a couple of times to check and sure enough, the water was cold. Also the dry cycle did not work any more. The dishes were still wet.

So I opened up the dishwasher and kept troubleshooting.

I checked the control board because I read somewhere that the relay was poorly designed and re-soldered the connection points.

I checked the heating element, resistance is 25 ohm which fits nicely with 230V and 2000 Watt, so that seems to be ok.

I looked at all (transparent) ducts and hoses. They look clean and in good shape.

Disassembled the pressure valves. They were clear and clicked when I put pressure on them.

Everything seemed ok so I did a test run. I left the casing open and put a regular light bulb parallel to the heating element, using some custom made wires.

When choosing a short program, without pre-wash and dry cycle, I noticed the following behavior:
The program starts.
The pump clears the device from water
The device takes fresh water in.
One or both (not sure) pressure switches click when the water level gets high enough.
The device keeps taking water in for a couple of seconds more, then stops.
The pump makes 2 starting attemps. Not sure if this is supposed to be this way, maybe to clear out air. On the 3d time (always) it starts running continuously.
There is some cavitation (air bubbles) going on and the pressure switches click occasionally.
Once the flow settles, no major air bubbles and a constant flow, the heater (and the light bulb) turn on.
The water gets hot within an acceptable time (5 minutes)

So far so good.
I ran an empty run with special dishwasher cleaning stuff.

But then the problem starts.
I close the dishwasher up again.
Install it back in the cabinet
Load it with some dishes and run a program.

The water stays cold, no matter what program I choose.

I wondered if the fact that there is dishes in there would make a difference. Maybe the water level gets lower and the pressure switch prevents the heating element to turn on. So I added 2 liters of extra water. No luck, the water still stays cold.

The fact that when I test it it all works but as soon when I build it back again it stops working drives me nuts.
I feel some sensor is preventing the heating circuit from closing but I don know which.

As far as I can tell there is:
– On/off switch
– Control PCB (relay)
– Pressure switch(es?)
– Door switch

The heating element is fine.
But the control pcb does not always decides that it is ok to switch on the heater.

O, and there is no error code as far as I know. No blinking LEDs and the program just finishes normally.

Anyone?

[aqualectric]

Re: AEG Favorit F55010 VI not heating up

Low insulation on the heater or PCB in that order. If you have a 500V insulation test meter then an insulation integrity test of the heater disconnected is the first thing to do. A normal multimeter will not find it. For information, the motor pulses as it is a tacho controlled unit that checks the head of water available before starting the wash cycle. A ‘no heat’ issue doesn’t generate a fault code on these; but the cycle will be longer.

[fixitall]

Re: AEG Favorit F55010 VI not heating up

Hi,
Thanks forthe quick answer.
I don’t have a 500V insulation tester unfortunately.

Still strugling in undestanding why bad insulation would have this symptom? I would expect that when the insulation deteriorates, eventually my gound-fault circuit interrupter would trip. But other than that, the heater would just work. Maybe you can explain it a bit more.

What I was actually thinking of myself as a next step is the wiring in the door. One of the wires runs directly between the PCB and the heating element and is neccesarry to close the circuit. It is part of the cable harness that flexes whenever the door opens,

The intermittent nature of the failure suggest a bad cable to me. It would also explain why the device runs for 3 test cycles without a problem, but when I install it again (opening the door to get to the screws), it stops working.
In between the test cycles I only open the door a little to access the controls.

What do you think?

[fixitall]

Re: AEG Favorit F55010 VI not heating up

Some more info…..

I decided to do some more testing and right now i am not sure about the symptoms anymore. This is what happened:

I installed the dishwasher in the cabinet again but this time with an external light bulb, parallel to the heater element. A bit weird but this way i actually have a visual clue when the heater comes on during operation.

I selected the ´auto´ program.
According to the manual this program measures the clearness of the water and adapts the cleaning program.
– prewash
– main wash on 45 or 70 degrees
– 1 or 2 intermediate rinses
– final rinse
– dry cycle

What I see is this:
– during pre wash the heater comes on (warm prewash?)
– during main wash the heater comes on
– The intermediate and final rinse, the heater does not come on
– the dry cycle doesn seem to work at all (no steam)

Then eventually the device times out (looks like). The red light goes off but there is no beep that normally signals the end of the program.

Plates are still wet.

So I wonder how the dry cycle works. What creates the steam? Is that the same heating element? How does that work since it seems that the pressure switches guard sufficient water level. Or does it just start heating up without flow so that steam is created?

This seems for now the clearest symptom I have.

Can anyone help in what I am supposed to see during the cycle?

Thanks.

Peter.

[Seamy]

Re: AEG Favorit F55010 VI not heating up

Maybe you could post PNC number 9 digit code off appliance as there are 60+ variants of F55010

Could be break in loom or P.C.B could have poor relay contacts (quite common on these).
Something else that could be causing probs’ is the Turbrity Sensor or connections to it, break in fine cable perhaps,

[fixitall]

Re: AEG Favorit F55010 VI not heating up

Hi,

It has been a while. Took some time to troubleshoot it a bit more.

During operation, couple of weeks, the behavior is quite unstable. It rarely switches on the heater although sometimes it does.

Today I disassebled it again, determined to find the darn root-cause.

I figured out the connections that are involved with the heater.
– Start at the power switch
– Then towards the pressostat
– The toward the heating element
– Then back to the control unit (relay)
– Then to the the power switch

When starting up a cycle I confirmed it is the relay of the control unit that is not switching. I can actually switch the heating element on at any given moment when I bridge those two contacts (I disassembled the front of the door so I could reach those contacts while running.

The question that remains is:
– Is the control board trying to switch the relay but does not succeed?
– Or is the control board not switching because it gets bad input (temperature sensor)

Since the control board is 230 euro´s, it as bit expensive to try it out.

I figured out where the temp sensor is and what cables connect it to the control board. I checked / measured the cables and found they are ok.

If I measure the resistance of the temp sensor however, I get the following:

Temp sensor has 4 contacts
– Between 1 and 3: 30.7 Kohm
– Between 1 and 4: 35.9 Kohm
– contact 2 is not connected to any of the others. That seems to be weird, unless it is not used. But then why put a cable to it.

So is this it? Did I found a defective temp sensor?

Any advise is appreciated.

[fixitall]

Re: AEG Favorit F55010 VI not heating up

The product number is 91193561607

[fixitall]

Re: AEG Favorit F55010 VI not heating up

Update:
Still trying to eliminate possible root-causes before having to exchange the controller.

I figured out I was looking at the turbidity sensor and looked into how these things work. The values I measured on the contacts might be correct. There is a common power lead, a temperature output, a return of the light source and an output of the optical receiver. This is the lead I did not measure anything.
So, there is no easy way to check a turbidity sensor as far as I know.

So I opened up the controller again and had a magnified look at the solder points and components. Nothing weird to see. I measured if any connections were interrupted around the relay that switches the heater. There were not.

So I connected everything in such a way I could measure directly on the board during operation. I wanted to see if the board did try to control the relay or that the relay itself was the problem.

I then did some test runs with different programs and try to figure out what was wrong or not:

– start 30 min program
– drains / fills
– 230V at controller relay becomes available (shows all other safetys work properly)
– Then the relay closes (12V on the board)
– Soap dispenser opens
This seems correct behaviour……

Reset / select auto program

– Start auto program
– drains / fills
– 230V at controller relay available
– Relay stays open / no 12 V ( pre-wash)
– 15 / 20 min run
– Soap dispenser opens (I expected a drain and fill in between)
– 10 min run (no heater coming on / no 12 V on the relay)
This seems incorrect behaviour…….

Reset / select 30 min program

– Start 30 minute program
– Drains / fills
– 230V available at relay
– Relay stays open (!?)
– Soap dispenser opens
– 10 minute run
– Hold program / open door. Measure temp of water: 29 deg C (hotfill)
This seems incorrect behaviour, it is suppose to run on 45 deg C.

Reset / select intensive care program (70 deg C)

– Start program
– drains / fills
– 230 V available at relay
– Relay open / no 12 V (pre wash)
– 20 min run
– drains / fills
– 230V available at relay
– relay stays open / no 12V (?!)
– Soap dispenser opens
– 10 minute run
– Hold program / open door. Measure temp of water (30 deg C)
– Continue program
– 30 minute run (no heater, temp of water the same)
This is definitely incorrect behaviour.

I am strongly suspecting the temp sensing part of the turbidity sensor / or the logic part of the controller.

It seems to work ok when the intake temperature is cold.
But when I do some test quickly after each other, the water intake is around 30 deg C and then the washer decides that is warm enough and does not heat up.

I will try to exchange the turbidity sensor first, since it is 30 euro.
I would hate to have to exchange the controller since it is 230 euro. That´s half of the price I bought the dishwasher for. Why having such an expensive part anyway except for warranty purposes?

I also read somewhere that at this point it is wise to bring in an expert since they usually have spare parts that they can try out and see if it solves the problem.
Thing is, if it is the control board I don want to spend 300 euro (parts + labor) on a 5 year old dishwasher.

Grrr.

[Martin]

Re: AEG Favorit F55010 VI not heating up

You still haven’t checked the insulation on that heater then huh?

Throwing parts at it won’t help much without first carrying out the elementary checks and earth insulation is a must do!

[fixitall]

Re: AEG Favorit F55010 VI not heating up

Hi Martin,

If you mean the 500V insulation test of the heater, no, I haven´t done that since I don´t have the equipment.

I still would like to understand what a low insulation in the heater would do and how it is related to the symptoms. Can you explain that a bit more just for information?

As far as my troubleshooting, I confirmed that the relay on the controller does not switch. It does not get 12V form the board. Why?, I don know.
In fact, when I bridge that relay manually, the heater works fine and the water heats up nicely.

So my conclusion was that it is the control board. That´s why I took it to a repair shop. They can confirm my conclusion and if repair makes sense, repair it.

[Seamy]

Re: AEG Favorit F55010 VI not heating up

Fit a new P.C.B, i’d dare to advise

[fixitall]

Re: AEG Favorit F55010 VI not heating up

To finalize this post, I got my dish washer back today.
Indeed, controller is defective. They came to the same conclusion I did.
Unfortunately they also had a problem when they fitted a used controller. They talked about a short circuit somewhere that killed the controller. They could not find what however.
So cost would be 200 + euro , and the risk the failure would come back again.
I decided against the repair. Disappointing. But the machine is just not worth it.

Now I need to let it rest.

[Author]

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