Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fault

[neon_3SP_glow]

Miele T/D T8422C.

Customer complains that the machine stops after a few seconds and flashes the cooling down light as well as sounding the buzzer.

The user manual mentions this:

The only other thread I could find on here was this:

post324534.html?hilit=t8422c#p324534

Any ideas please? This machine is way out of my usual area. But, customer is willing to pay as apparently booking a Miele engineer takes too long!

Thanks all, Daniel.

[electrofix]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

is this on an auto setting or timed dry do you know

Dave

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

electrofix wrote:is this on an auto setting or timed dry do you know

Dave

I don’t know Dave.

Can i ask what the diff might be for when i go to take a look?

Thanks.

[electrofix]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

with a timed dry it may not be using dryness sensors and will do the whole programme regardless of dryness but on the auto prog it senses the moisture

my be a silly fault. there are a set of brushes running on the drum to sense moisture

there also may be no heat at all. most have a relay board to switch elements and I have had them go

there is also overheat stats on element

Dave

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

electrofix wrote:with a timed dry it may not be using dryness sensors and will do the whole programme regardless of dryness but on the auto prog it senses the moisture

my be a silly fault. there are a set of brushes running on the drum to sense moisture

there also may be no heat at all. most have a relay board to switch elements and I have had them go

there is also overheat stats on element

Dave

Thanks for the heads up.

I’ll let you know how I get on!

[electrofix]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

there are some tech manual for miele here

https://www.manualslib.com/brand/miele/dryer.html

mostly American stuff but some tech cant be all different. does not have your unit as a tech but others may give you an incite

look for the technical info tags

Dave

[Kentish]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

Could be drum brushes worn, or temp probes issue. Haven’t had no heating causing rapid change to cooling down, as normally the machine keep running.

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

As promised, here’s an update after visting the machine.

The drum moisture brushes were fine.

The thermal limiter on element box is good.

No visible signs of damage on the Element relay PCB, however, at no point did the element ever get a Neutral. The Left most Relay (when looking at relay pcb from above) never allowed the Neutral through to complete the circuit and as such the machine never heated.

That’s either because the Relay is faulty, or the sensors are preventing the relay control circuit from activating.

Now I understand it, i think!

The Sensor probe located in the element box read: 138kOhms
The probe located under the door read: 13kOhms

These readings were at room temperature and both probes lowered their resistance when i warmed them with my fingers.

Can I ask if anyone know’s what kOhms these probes should be reading when working correctly at room temp?

Thanks.

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

neon_3SP_glow wrote:As promised, here’s an update after visting the machine.

The drum moisture brushes were fine.

The thermal limiter on element box is good.

No visible signs of damage on the Element relay PCB, however, at no point did the element ever get a Neutral. The Left most Relay (when looking at relay pcb from above) never allowed the Neutral through to complete the circuit and as such the machine never heated.

That’s either because the Relay is faulty, or the sensors are preventing the relay control circuit from activating? Is that correct thinking?

Now I understand it, i think!

The Sensor probe located in the element box read: 138kOhms
The probe located under the door read: 13kOhms

These readings were at room temperature and both probes lowered their resistance when i warmed them with my fingers.

Can I ask if anyone know’s what kOhms these probes should be reading when working correctly at room temp?

Thanks.

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

According to this manual:

https://www.manualslib.com/manual/83192 … =32#manual

Which is for a Miele model T9800…

[Edit – I think the sensor in the element box is actually an 1R30, its one or the other!] The R230 thermal sensor (which is located in the element housing) should have resistance readings as outlined in attacchement…

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

Regard the thermal sensor located under the door. Here are the respective readings:

Again, this corresponds with the values I tested (13KOhms = 22’C ish)

So, it looks like both sensors are working correctly. This leaves me to deduce the fault is in fact on the relay board. Specifically, the relay which switches the Neutral to complete the element circuits.

Cheers.

[electrofix]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

you can check that by measuring the relay coil voltage

Dave

[neon_3SP_glow]

Re: Miele T8422C Tumbe dryer | Cool Down light and Buzzer Fa

Hello guys.

Just a quick summary for the benefit of anyone reading this thread in the future.

Renewing the relay which activates the neutral cured the fault. Whith a new relay the machine heated as normal.

Although the relay didnt show any visual signs
of damage, when i desoldered it i notice on of the legs dettacthed. Possibly a result of my man handling.

Glgl

[Author]

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