Tumble Dryer Heating then Cooling

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Hi all, we have a Zanussi ZDC47100W condensing tumble dryer. It was made in 2008, used very little and given to us in 2017. We’ve used it since with no problems – cleaned the filter after every dry, kept the condenser clean as per the instructions, etc.

It’s barely used in the Summer, but because it’s been so damp and cold we’ve had to use it occasionally. When we went to use it last, it heated up but then cooled down after about one minute. The rest of the cycle carried on to completion. Since then, it will heat up only to cool down shortly after start up.

I’ve taken the back off it and carefully accessed the heating elements. When a new cycle is started, the elements very clearly work so I’m ruling that out.

I’m thinking it’s the temp sensor, so I bought a new one and I’m due to fit it this evening. Before I do, is there anything else obvious I could be missing? I couldn’t find a thermostat listed and there was nothing else I could think which would cause this issue. No warning lights although the ‘condenser’ light did illuminate red once at the end of a cycle. It’s never lit up since.
 
Try shorting the sensor out, if it works ok then that confirms your suspicions. But DON'T run it like that for a full cycle
 
Try shorting the sensor out, if it works ok then that confirms your suspicions. But DON'T run it like that for a full cycle

I've bought a new one so I am going to replace it seeing as I have it. It's fairly straightforward to get to.

I couldn't think what else it could be. If the elements were heating up successfully, then something had to be stopping it heating up.
 
You're sure there's nothing clogging the airflow?
 
You're sure there's nothing clogging the airflow?

First thing I thought when I initially saw the condenser light, but the condenser itself is clear and the two filters clear. The 'air in' port at the back looks a little dusty so can't think why this would cause overheating. The 'hamster wheel' type cylinder spins freely when the dryer is switched on. Couldn't find anywhere else to look.
 
Hopefully it is the overheat sensor, however in my limited experience, they are all or nothing. By that I mean that a faulty one will prevent the element heating at all.
 
Hopefully it is the overheat sensor, however in my limited experience, they are all or nothing. By that I mean that a faulty one will prevent the element heating at all.

I'm with you. Hopefully it's the former! It was about £14 I think for a genuine one, so hopefully it works! It's too good not to at least give it a go.
 
First thing I thought when I initially saw the condenser light, but the condenser itself is clear and the two filters clear. The 'air in' port at the back looks a little dusty so can't think why this would cause overheating. The 'hamster wheel' type cylinder spins freely when the dryer is switched on. Couldn't find anywhere else to look.

Have your heard of the "secret hatch?"

 
Have your heard of the "secret hatch?"

No, I haven't if I'm honest! Sounds like where I should keep my bars of Dairy Milk. Thought I'd explored all the doors and covers for user-serviceable parts.

Where should I be looking?
 
Thought I'd update on this. Replaced the temperature sensor last night and this seems to have solved the problem.

I took the old one out and it was a little bit 'gunky' with an unknown substance on the surface, and replaced with the new one. The sensor slides through a rubber grommet with only the socket at the top protruding from it. It only involved taking a side panel off -- access was easy.

Did a trial run and after ten minutes, the heating elements were still on. No burning smells or warning lights. Happy with that.

If anyone finds this with a similar problem, shop around for the temperature sensor. I got a genuine Zanussi one for less that £15, but many sites sell for upwards of £40.
 
Well played.

I do recall, years ago replacing the sensor on an old hotpoint. The advice was to throw the sensors at the floor to get them working. I ignored, what may have been sound advice, and decided to pull the unit out once only, and accordingly purchased a new sensor.

Anywho, well done and thanks for the update.
 
Well played.

I do recall, years ago replacing the sensor on an old hotpoint. The advice was to throw the sensors at the floor to get them working. I ignored, what may have been sound advice, and decided to pull the unit out once only, and accordingly purchased a new sensor.

Anywho, well done and thanks for the update.

Oh wow that brought back a childhood memory. Mum used to have 'Hoover' branded stuff and I remember the washing machine man removing something and tapping it with a hammer!
 
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