Washer dryer not heating on dry cycle
A washer dryer not heating on the drying cycle will leave laundry cold and wet. The heater is an obvious first suspect, but in most cases the thermal overload cutouts (TOCs) or thermostats are the more likely cause.
Step 1 – Check the Heating Element
The heater used on the drying cycle is entirely separate from the one used on the wash cycle. On a washer dryer, the drying element is accessible from the top of the machine and has two clearly visible connectors for live and neutral.
Before testing, pull the wires off at least one of the element’s tags to prevent false continuity readings. Then test continuity across the element terminals with a multimeter. A working element will show a resistance reading – typically somewhere between 30 and 50 ohms. If the reading shows open circuit or very high resistance, the element has failed and needs replacing.
If a 500v insulation tester is available, check the insulation resistance from each terminal tag to earth. A leakage reading below 2 megaohms indicates the element is unsafe – it may blow fuses and should not be used. Any measurable leakage to earth is a concern and should be investigated.
Step 2 – Check the TOCs and Thermostats
If the element tests correctly, the TOCs (thermal overload cutouts) and thermostats are the next suspects. On a washer dryer, these components are located on top of the tub alongside the other drying parts, making them relatively easy to access.
TOCs are normally closed-circuit devices – they go open circuit when they blow. Test each one for continuity. An open circuit reading indicates the device has tripped or failed.
Some TOCs include a small reset peg in the centre. If one is found and pressed after the device has cooled, a click should be heard as it resets. However, if a TOC trips again after being reset, the underlying cause of the overheating must be found – the device should not simply be reset and ignored.
If a TOC Has Tripped – Find Out Why
TOCs are thermal fuses. They are designed to trip only when the temperature rises to a dangerously high level. Finding a tripped TOC should prompt investigation into the root cause of the overheating, not just replacement of the device.
Common causes of overheating that can trip a TOC are listed below. Work through these before replacing any safety devices.
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Stopping the dryer mid-cycle. Opening the door or turning the dryer off while it is running causes the fan to stop. Latent heat from the element can then build up rapidly and trip the TOC before it dissipates.
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Overloading. A washer dryer can always wash more laundry than it can dry – often significantly more. Exceeding the drying load limit restricts airflow and causes overheating. Remove some laundry before starting the dry cycle if the drum is full from the wash.
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No cold water to the condenser (condenser washer dryers). Condenser washer dryers require cold water to run into the condenser chamber during drying. If this supply is interrupted, or a blockage prevents condenser water from draining, overheating will result.
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Faulty temperature sensor or stat. A failed sensor may report incorrect temperatures, causing the control system to allow the element to run beyond safe limits.
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Faulty or non-running dryer fan. If the fan fails or is not running at the correct speed, heat cannot be circulated and removed from the heating chamber, causing rapid overheating.
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Fluff and lint blockage. A build-up of fluff inside the heating and fan chamber restricts airflow and is a common cause of overheating across all washer dryer brands. This appears to be a design characteristic rather than a fault in individual machines.
Testing Tip – Timer Setting
When testing whether the heater is working on the drying cycle, be aware that the first 10 minutes on the timer dial typically apply no heat. To confirm the heater is energised during testing, turn the timer to at least 30 minutes. Testing at a low timer setting may give the false impression the fault has been fixed when the heater simply was not activated.
Frequently Asked Questions
Why is my washer dryer not heating on the dry cycle?
The most likely causes are a tripped thermal overload cutout (TOC) or failed thermostat rather than the heating element itself. Check the element for continuity first, then test each TOC and thermostat for open circuit. If a TOC has tripped, investigate the cause of overheating before replacing it – common causes include overloading, a blocked lint chamber, or a non-running fan.
What is a TOC on a washer dryer?
A TOC (thermal overload cutout) is a thermal fuse that protects the appliance from overheating. It is normally closed-circuit and trips to open circuit if the temperature exceeds a safe level. TOCs are deliberately designed to blow under extreme heat to prevent fires. Finding a blown TOC should prompt investigation into why overheating occurred, not simply replacement of the part.
Can I bypass the TOC to test if it is the problem?
No. Bypassing a TOC or any thermal safety device removes the only protection against the appliance overheating to the point of catching fire. This is extremely dangerous and must never be done. Test the TOC for continuity with a multimeter instead.
How do I tell the difference between a TOC and a thermistor?
They can look similar, but thermistors are usually slightly larger. A TOC reads as a closed circuit when working correctly and goes open circuit when blown. A thermistor reads open circuit at room temperature and gives varying resistance readings as temperature increases – so an open circuit reading at room temperature does not indicate failure. See: how to test an NTC thermistor.
Thanks Peter. Yes if it trips again quite quickly you need to find out what is causing it to trip. Some clues would be back in my article.
BOSCH WFT2800/13 WASHER/DRYER
Grateful thanks Andy for info on dryer element. I was about to replace the element when I read your advice above. Good job I did ‘cos the dryer element isn’t the same as the washer element. As your article suggested looking at the TOC at the top of the machine, I did just that, pressed the plunger which clicked home, switched the machine on for 10 mins and all seems well. Hopefully it will remain that way unless there happens to be another gremlin in the works that causes a trip condition?????? I also read about the possibility that the cause would need investigation if it occurs again so fingers X’d.
Kind regards,
Peter 10 March 2015