Miele TDA 150 C tumble dryer...

[Jethro 78]

Miele tumble dryer 3,5 years old no longer gets warm. Also does not warm on the "warm air program". Intermittent F2 error, but this disappears and the signal from the rear NTC is good.

I have done the whole round of checks, both NTCs, both heating elements, thermostat switch. Power relays click over after about 60 secs.

One odd thing, after power relays click voltage between heating element leads and ground is 120V. Voltage between heating elements and return lead is 0V. Is this normal?

Any ideas? Thanks.

 

[blup]

Faulty rear NTC or it’s wiring connection?

Blup

 

[Jethro 78]

I checked the rear NTC signal up to the power board. It responds as it should with temperature and is in line with the Miele specs.
Does the "30 min hot air" program bypass the NTC signal?

 

[Jethro 78]

The rear NTC was 150 k Ohms at 20C and went down to 9 k ohms at approximately 85C.

It's interesting that the F2 error appears once but will then be removed after I enter the service mode.

 

[blup]

You need a Miele service engineer for that.

Blup

 

[jj4091]

Miele tumble dryer 3,5 years old no longer gets warm. Also does not warm on the "warm air program". Intermittent F2 error, but this disappears and the signal from the rear NTC is good.

I have done the whole round of checks, both NTCs, both heating elements, thermostat switch. Power relays click over after about 60 secs.

One odd thing, after power relays click voltage between heating element leads and ground is 120V. Voltage between heating elements and return lead is 0V. Is this normal?

Any ideas? Thanks.

So are you saying that there is a voltage of 120v ac between each of the wires & earth when disconnected from the element? What is the voltage across the wires when disconnected from the element? Is the drier protected by an RCD?

 

[Jethro 78]

Dryer is protected with rcd.
When element is disconnected:
Contact on pcb for large element is 136v to earth
Contact on pcb for small element is 2v to earth
3 rd contact is 3v to eath

 

[Jethro 78]

20210127_202306

• Jethro 78
• 27 Jan 2021

Miele t150c pcb

 

[Jethro 78]

10v between small and large element conact
1v between small element and 3rd contact
16v between large element and 3rd contact

 

[Jethro 78]

I must apologize that I am not the best electrician...but it seems to me that the two elements are parallel? and therefore should be getting 120V?

 

[jj4091]

I must apologize that I am not the best electrician...but it seems to me that the two elements are parallel? and therefore should be getting 120V?

I think you are meaning that the elements might be in series rather than in parallel across 240v ac so that you are reading 120v across each one. I think they should each have an individual supply of 240V but diferent ratings (Kwatts) for different drying levels.
The readings you are supplying are really strange which to me suggest a pcb or wiring fault.
Sorry I am not familiar with Miele products so not sure exactly how thy should perform I'm just giving generic answers that would apply to other manufacturers driers.

 

[Jethro 78]

Thanks for you help jj4091. I am leaning towards a PCB fault myself. There has been documented failures of the relays on these PCBs...
I read in a Miele repair manual (for an older model) that both PCB relays must close to send power to the elements. Perhaps only one relay is closing?