The most common causes of a tumble dryer not heating up are either a faulty heating element, or a faulty stat (or TOC). A TOC is an acronym for thermal overload cutout and it’s essentially a heat activated fuse. Other common causes are faulty connections, and float switch or condenser sensor faults in condenser dryers.What does a stat or TOC? look like and what do they do?
A TOC or Stat
A stat (or thermostat) is designed to reset when it cools down. They are used to control the temperature of the dryer by regularly switching the heater on and off. A TOC is designed to protect against overheating and normally would not re-set if it triggers. They are designed to only operate under dangerous temperatures.
Generally speaking a device like this is normally closed circuit. If found to be open circuit it has failed. But if it’s a stat and not a TOC a lack of continuity could just be a high resistance through heat sensitive crystals. If you aren’t sure if it is a stat or TOC don’t guess.
Warning
Where are the stats and TOCs?
They should be very close to the heating elements. Some dryers have a back panel which can be removed and it’s possible they may be accessible from there, but some will have the heating element and stats at the front of the dryer so it may need stripping down to get to it. Some stats may even be hidden away, for example, monitoring the airflow out (if vented).
Generally speaking if you can’t see one by removing a lid or back panel I’d advise not stripping it down – especially if a condenser dryer – as many dryers can be a right pain to strip and reassemble if you aren’t an engineer.
How to test a stat or TOC
They are tested with a simple continuity test meter. If there is no circuit from one tag to the other it’s generally because it’s failed.
Will replacing a TOC it fix the fault?
Not necessarily. Although these devices can fail for no apparent reason, they usually fail because of overheating due to another fault. In other words, a failed TOC could just be the symptom of an overheating fault in the same way as a normal fuse in a plug is the symptom of a different fault. If a TOC has gone you need to work out why..
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Sometimes they can go for no apparent reason. On vented dryers a blocked or severely kinked vent hose can also cause overheating. Stopping a dryer mid-cycle can cause the overheating stats to fail on some dryers so don’t stop one mid-cycle (see don’t stop a dryer mid-cycle).
Useful tip
Faulty Heating element
Another cause for a dryer not heating is of course a faulty heating element. However, replacing an element in a dryer is often much more involved than most people would think. Many tumble dryers would need completely taking to pieces. Some simple vented dryers though have heating elements that are more easily accessible by removing the back panel, and can be tested for continuity or checked for obvious breakage.
Some can just have a small compact heating element inside a metal housing, which slots in and out of the back easily – but most others have large heating elements inside, which aren’t accessible without stripping the dryer down.
A faulty element could be obvious by being physically broken or damaged, but if not, the only way to test one is with a continuity test meter to check that there is a complete circuit all the way through it.
To see what tumble dryer elements look like, and the variety of different types fitted, look at this spare parts catalogue of dryer elements
Micro switches and sensors
Condenser dryer float switches: If you have a condenser dryer it will be designed to cut off the heater via a float switch if the drawer or compartment holding the condensed water gets full. If the dryer stops heating check the compartment has been emptied of water – although most condenser dryers now should have some way of informing the user that the drawer needs emptying such as via a flashing light. It is possible for one of these float switches to go faulty, or stick, therefore triggering the warning when the chamber is empty preventing the heating element from switching on.
Summary of common causes of a tumble dryer not getting hot
- The heating elements can fail (open circuit) or have a faulty connection
- There are cut-outs and stats that can trip out or go open circuit (discussed at length above)
- Faulty connections and burned wires
- Condenser dryers can have float switches or sensors which cut the heater off if the water hasn’t been emptied out of the condenser drawer, check the water is emptied, these sensors and switches can also go faulty
Mike Perry says
Some tumble dryers, such as the Hoover HDV6UK, also have a safety cutout in series with the thermal cutout. The thermal cutout is available as a spare from from many suppliers – but none can supply the safety curtout for some odd reason. It is mounted adjacent to the thermal cutout and wored in series, it is mounted in exactly the same way and is as easy to change. I wonder why no one stocks this essential safety item?
Whitegoodshelp (Andy Trigg) says
I can see 4 TOCs available on 4Washerhelp spares although one of the parts is the complete element housing which looks like it comes with both tocs http://www.4washerhelp.co.uk/dryer-element/product.pl?pid=453688&query=HDV6UK
There are 3 other tocs or “stats” listed for this model, if in doubt you could always contact the guys at 4Washerhelp to see if it’s avaialble.
http://www.4washerhelp.co.uk/search.pl?t=50174.1558022747&query=HDV6UK
Mike Perry says
But they are not the safety cutout that I need! They are the thermostat that is wired in series with the safety cutout! The thermostat works but the cutout is O/C and is not resettable.
Whitegoodshelp (Andy Trigg) says
There are 2 thermostats, a thermal fuse 1 shot cutout and the complete heater with stats listed. If it isn’t any of them give them a ring or send them a part query. It’s not likely that a part like that is not available.
Mike Perry says
On the top of the heater casing are two thermal devices. The right hand one, when viewed from the back, is the thermostat that controls the heater temperature by sensing the air coming out of the element area and being fed into the drum. The other device, to the left of the black thermostat, is a while ceramic bodied thermal fuse that is non resettable. It is that which commonly fails if there is any slowing of throughput of air (often caused by a build-up of fluff in the pipework after the lint filter). It is that cutout that I am trying to source. I have had a liong discussion with Hoover but they will only supply a complete heater assembly (very wasteful) or the thermostat. They claim not to know where the thermal safety cutout is sources from as they buy-in the heater as a complete sub-assembly and claim to have no record of where the cutout comes from nor who supplies it to the sub-assembly manufacturer. All of which falls foul of European safety laws! I know that Hoover should be keeping records of where all the parts they use are supplied from, even for any sub-assemblies bought-in complete. But they claim not to have that information so I feel they are trying to profiteer by selling only complete heaters at more than £60 according to their spares website (but available elsewhere for £33). All I want is that safety cutout, nothing else.
Why should we be forced to discard perfectly good materials for the want of 1 small item? And that is one that is so easily replaced anyway – if you can get the part.
(I spent many years working for a major rental company as initially a service engineer and subsequently as a Training Manager, our role included teaching white goods servicing as well as TV, video, audio, CD, satellite and camera servicing and maintenance.)
Whitegoodshelp (Andy Trigg) says
Hi Mike. What I’m confused about is that the thermal fuse is listed here for that model
http://www.4washerhelp.co.uk/thermal-fuse/product.pl?pid=1145395&query=HDV6UK
They should by law provide all functional spares for a specific period (it used to be 10 years but it’s probably less these days) but I presume they can get away with supplying it as part of another unit by saying it’s still available. They (and most other manufactures – not just appliances) have been doing it for decades now.
There are many worse examples such as all the manufacturers who no longer supply seals, bearings, drums, drum shafts and only provide a complete sealed outer tub. Also, most manufacturers no longer supply bearings or armatures for motors – only a complete motor. It’s crazy but they all do it. It’s all about the finished product, and not maintaining them, but presumably they might argue it also keeps prices down.
Mike Perry says
Hi Andy
That looks like the thermostat to me. I have a picture taken of the assembly showing the actual part needed, I can supply that to help if there is some way to send the image to you. I can supply an email address if that helps but don’t want to put it on such a public forum. Instead, if you can see my address as used for this site, you are welcome to contact me direct if that helps?
Seems to me that there is a difference in terminology and hence some confusion. From my researches, the black bodied devices are a thermostat that cycles the heating elements on/off to maintain a fairly level temperature of the air flow. The white ceramic bodied device is a non-resettable cutout that trips if the air gets too hot for a protracted period, shown initially by the ‘Filter care’ warning light, but that also illuminates if there is insufficient airflow to disperse the heat and that is what has happened to ours.
Many thanks for your help
Mike Perry
Whitegoodshelp (Andy Trigg) says
Hi Mike, it’s described as a thermal fuse, and even says “one shot” so as far as the description is concerned it is definitely the part you need. It’s also a different part number and price to the others, which are labelled “thermostats” and have temperatures (55 degrees) listed in their description. Therefore regardless of the photo I would assume that is the part and if you order it and it isn’t you can send it back for a full refund.
It seems very strange to me that they would provide all the stats and small parts except a toc. Colours could vary or the photo may even be wrong but as long as it doesn’t say its a thermostat on the part and has similar description to the original it should be the part.
Mike Perry says
Looks identical to the thermostat, even to the relationship of the electrical connections to the mounting holes. It even looks to have the bulbous underside, judging only from the image shown (look at the edge where the black body meets the metal plate), that is a characteristic of the thermostat but not of the cutout – that has a flat underside that sits flush with the top plate of the heater box! Agreed that the description appears to suggest it is the cutout from the ‘one time’ epithet, so they may have used the wrong photograph – which definitely does not help. I will try ordering one and if it fits, then we’re all happy, else it will have to be returned.
Thanks for your help.
Mike Perry
Whitegoodshelp (Andy Trigg) says
I think your toc is flat because it’s tripped. They all have bulbous underside, which depresses in under specific temperature and moves the switch inside. They are essentially exactly the same in every way except calibrated for different temperatures and the stats are designed to reset when cooled, but a one shot thermal fuse is not.