White goods - tumble dryer fault.

[julianf]

So we have one of those generic condenser dryers. I think it's an hotpoint, but they're all from the same factory.

It has an element pack on the back, with a couple of elements and some thermal fuses, which, I assume, auto reset.

The issue is that, somtimes the unit wont heat. A cold reboot seems to cure it some, but not all of the time.

But other times it's fine. So it's not something simple like elements gone.

Do those thermal fuses (well, I guess they're just temperature dependent resistors read by a micro somwhere, rather than fuses) age?

When you buy the replacement element pack it comes with the fuses, but I can't find anything wrong with the one I've got.

What do you reckon?

(And, yes, I've cleaned all the air ways, so it's not an air restriction causing overheating, fan is all fine, etc)

 

[gaz1]

if it works and then dosnt work its not the elements or the thermal furse

its more its controler

 

[julianf]

Ps.

Mine is back together again now, but the elements look like this -

With the temperature fuse things on the top. I can't say I understand the wiring though.

 

[julianf]

if it works and then dosnt work its not the elements or the thermal furse

its more its controler

Was wondering if the sensitivity was wrong. So it was effectively going to 'lockout' at too low a temperature.

 

[gaz1]

you forgot the fan issue if it wont spin then it shuts down the heating element

id say a pcb board problem with the controller part of the board

a reset would reset the control board but later the error would come bacck again

 

[Barking Mat]

You haven't got a blocked vent, causing overheating?

 

[julianf]

(And, yes, I've cleaned all the air ways, so it's not an air restriction causing overheating, fan is all fine, etc)

 

[bourbon]

Check the Hotpoint website. There has been a MASSIVE recall on faulty tumble driers. Yours may be one affected. Be prepared for a fight to replace it though.

 

[waldershelf]

Had a problem with our 20 year old White Knight vented tumble dryer only last week. elements both failed, rear bearing shot and the fan duct had split. I could have repaired it for less than £100 but SWMBO says no, we'll have a new one. So we have nice shiny new dryer that wont last 20 years and wont be repairable when it does go wrong.

 

[WorkshopChris]

Those are thermostatic switches open/close at a set temperature they will either work or fail. A reset will have absolutely no effect on them so that's not where your problem is.

 

[julianf]

Those are thermostatic switches open/close at a set temperature they will either work or fail. A reset will have absolutely no effect on them so that's not where your problem is.

So the things mounted on the element housing are switches then, rather than a sensor for a controller?

I was trying to work out the wiring - in the photo above there are 4 wires comming through to the heater unit. I'm trying to work out what the functions are if there is no feedback?

Possibly the reset is coincidence - I mean it does not always work so maybe I'm totally mistaken and turning it off and on again is actually completely irrelevant - which would be a good thing as that may go back to faulty switches, I guess.

 

[julianf]

Does anyone have any explanation of the wiring of the heater unit (ie why 4 wires required)?

 

[Country Joe]

The two wires run directly to the element, but through those thermal switches, which can cut the supply in a similar way that a thermostat would.
It should come back on again on it's own when it cools a bit - but not just stay on cold.

All the Best,
CJ

 

[julianf]

The two wires run directly to the element, but through those thermal switches, which can cut the supply in a similar way that a thermostat would.
It should come back on again on it's own when it cools a bit - but not just stay on cold.

All tghe Best,
CJ

...but there's 4 wires to the whole heater unit (from the main machine)

What I mean is, if it were all self controlling, with no feedback, just the live and neutral would be required.

Even if it had two heat settings, with a center tapped element, then that's 3 wires, not 4.

And why the two thermal switches?


I'm trying to understand what's going on to help me in my diagnosis.

 

[julianf]

...and, yes, the unit stays on cold. Does not switch on and off like a thermostat would. So, whatever the fault is, it's latching.

 

[Country Joe]

I can't quite see where those wires go at the side - is there a side view?

I assume there are two of them so that it allows for there being any hot spots on the large deflector plate - or maybe just a belt-and braces approach.
And if either one of them is over-temp, then the element power is cut until the temp drops.

Also, possibly with the recent well-documented fires, someone somewhere thought that using just the one would be more risky?
Maybe those rogue Hotpoint dryers only ever had one thermal switch?

I thought that maybe there is a wire (or wires) that run directly to the element, as only the one wire would need to be switched to cut power to the element.

I'm sure it would seem more clear if you could see the actual route the cables took.

Not much help, I know!
All the Best,
CJ

 

[julianf]

I'll take the unit here apart again and take some photos. Probably not till tomorrow though.

 

[Country Joe]

I'll take the unit here apart again and take some photos. Probably not till tomorrow though.

Don't put too much work into it - I might not have the answer - then I'll definitely feel un-helpful!
I don't doubt that others will, though!

All the Best,
CJ

 

[Barking Mat]

Is the two sets of wiring, warm and hot?

 

[Country Joe]

Is the two sets of wiring, warm and hot?

I hadn't considered that!
For some reason I didn't think of it having more than one setting!
I tend to use a de-humidifier, mostly.

All the Best,
CJ