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Daniel
Daniel, Home Appliance Technician
Category: Appliance
Satisfied Customers: 16772
Experience:  20+ yrs. experience in white goods repair. NVQ Level 2 electronics manufacturers training courses.
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I have Zanussi ZDE 47100 W. Situation: warms up, during the

Customer Question

I have Zanussi ZDE 47100 W.
Situation: warms up, during the normal operation, the start/pause button flashes red.
Actions taken:
I clean the filter regularity, as I always have.
Removed the filter, looked inside and the duct seems clear.
I recall last year, incidents that the tumble dryer never stopped, and clothes were damp. I put it down, probably incorrectly to recycling damp air, as I had a cracked flexi duct tube, which I had replaced.
Is it that a faulty thermostat can cause the alarm, which the manual diagnosises as filter blocked.
If so where is this thermostat located - I hav not found a technical drawing of the unit yet. How accessible is it from the front of the machine, as I have it mounted up high, and in a tight space.
Submitted: 1 year ago.
Category: Appliance
Expert:  Daniel replied 1 year ago.

Hi

The thermostats are located on the back of the heater element at the back of the dryer. You need to remove the buldge cover on the back there you will see the heater. Remove this and turn it over and there you will see 2 thermostats. You need to test them for contonuity. If any are faulty then you neeed to replace the heater as it comes as a complete unit

There is also an NTC sensor probe in the air dut. To access this you need to remove the top and then remove the right hand side panel.

Then looking at the bottom left corner you will see the NTC sensor there. It will have to thin wires to it.

Again with you multi meter test the resistance. Its usually around 7K ohms roughly so if out of range or open circuit then you need to replace the NTC sensor.

But if you find the heater/ thermostats and the NTC sensor are all fine then all thats left is the control board. In this case the board will need to be replaced.

As on vented dryers all you have in there is heater, NTC ,control board and motor. Now a motor wont cause it to stop and flash the start light.

So check the heater at the back and the NTC on the bottom right hand side and if they are all ok then you are looking at a circuit board fault im afraid.

If you need anymore info just get back to me.

Regards

Customer: replied 1 year ago.
Thanks Daniel,
This will take me a few days to check and get back to you. With day job and young kids .
What does NTC stand for , is it 'thermal conductivity', for dampness indication for this 'six sense' for electrical efficiency-stop when dry.
Is my interpretation that temperature sensors are being used by control, some how, to indicate blocked filter. And there is not actually a flow/ pressure sensor. Ie if temperature indicates low (by fault) but heating is active, then this in interpreted as low flow, and a blockage? So all the manual instructions to 'clean filter' is a bit of red herring?
Expert:  Daniel replied 1 year ago.
NTC stands for Negative Temperature CoefficientIt's basically a resistor which changes resistance with temperature. So the NTC sends the resistance back to the control board so the control board knows what temperature it is inside the drum. So if the NTC goes out of range the control board picks up there's a problem in there.The reason why the manual says to check the filters is because the odd time if it's a blocked filter or vent it can cause problems. But if the air flow coming out at the back is good then the air flow is fine.
To be honest we never got problems with air flow on vented dryers.
Daniel and other Appliance Specialists are ready to help you
Customer: replied 1 year ago.
Daniel,
I finally got around to check the thermistors with a multimeter.
The reading of each of the two units is only circa 2 Ohms.
When I short the two probes of the multimeter, they are also circa 2 ohms.
So I think in effect there is no resistance in each of the thermistors.I checked the heating element with multimeter.
A bit tricker, but there is continuity .My observation is that the thermistors also seem to be integral to the heating unit. I can't reality remove the thermistors. Am I correct? I have to rep,ace heater and thermistors as a full unit.?
Expert:  Daniel replied 1 year ago.

If you got 2 ohms on both the thermostats then they are ok. It will be faulty if you didnt get a reading on them so as you got 2 ohms then they are fine.

So you need to check the NTC sensor on the right hand side and see what you get on that.

But if thats all ok as well then its looking like a faulty control board here im afraid.

Customer: replied 1 year ago.
Hi Daniel,
I checked NTC and it was 6 ohms.Is faulty control board worth the cost to change it. Vs purchase new machine.Ps , your instructions were spot on- description of where items are, and how to access were spot on!Andrew
Expert:  Daniel replied 1 year ago.
Ok I assume you mean 6k ohms (6000) ohms. If so then the NTC sensor is fine.In that case then it's looking like he control board at fault.Which to be honest probberly not really worth the repair as you are looking at over £120 just for the part so it will be an expensive fix. Personally if it was me I would replace the dryer
Customer: replied 1 year ago.
Hi Daniel, no not 6kOhmns, but 6 Ohms.Andrew
Expert:  Daniel replied 1 year ago.
Ok 6 ohms isn't right. As a NTC sensor should be high resistance of around 7K ohms in Norma room temperature. So if you have just 6 ohms then it's way out of range. So in this case you need to replace the NTC sensor and see how it goes from there.