We have a Whirlpool tumble drier (about 5 years old), on which the red warning LED, which means that the lint filter needs emptying, keeps lighting up when there's hardly anything in the filter, so it's not drying clothes (and it's been pissing it down with rain all weekend here). Doesn't appear to be anything else blocking the ventilation pathway either.
Is this symptomatic of anything obvious that can be fixed?
We had a Whirlpool tumble drier that started doing that too.
You can try vacuuming out any loose lint in the filter housing.
If it's a condenser model you can try cleaning out the heat exchanger unit. (Beware: If you haven't done it for a while dirty water may gush out over your floor.)
However we kept the lint filter and the condenser heat exchanger clean and the warning light still kept coming on so we just learnt to ignore it. It ran happily like that for some years (until the drive mechanism seized up at
10 years old and we got a new dryer).Kind of begs the question what exactly is the light using as a sensor? Could it be that its overheating and its really a thermostat issue? Brian
Good question. I can think of a few ways of detecting a blocked filter:
1) Pressure on the feed side relative to atmospheric. 2) Pressure across the filter. 3) Volume of air flowing. 4) Temperature of air flowing. 4) I don't like, it's not fail safe. As the filter gets more and more blocked I can see the temp of the air flow (because there isn't very much) not rising above the threshold. So, to the dumb user, the fault appears to go away. 3) Air mass sensors are common enough in cars but I think they are bit delicate and all we need to know here is air flowing freely not how much air is flowing. Also electronic rather than a passive switch.Which leaves 1) or 2). 1) is the simplest, just a connection into the "high pressure" side of the filter, leading to a chamber with a diaphragm across it open to the atmosphere the other side. Pressure goes up diaphragm moves operates switch. Tube feeding it could get blocked. Very similar to water level detection in washing machines.
Another way in an airflow which isn't too hot is to use a thermister which is self-heated (by current flow) and relies on the draft to cool it. Read off voltage across it. If the thermister itself was covered in lint, that would trigger it.
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