Many people believe the washing machine isn’t heating up water when they can't feel any hot water through the door. But if the washing machine appears to otherwise work OK and the laundry comes out clean it may not have a fault (there are exceptions to this explained later). The water is only hot inside the washing machine for a small amount of time during a wash. Many washing machine doors also have an outer plastic insulating cover so it's sometimes hard to feel any hot water. Another factor is that modern washing machines put so little water in on wash, that hardly any warm water splashes up the door glass like it used to.
Is the laundry coming out dirty?
Sometimes people think the heater isn’t working because laundry isn’t coming out clean. You should still read this article. However, you should then read this article too – Washing not getting clean in washing machine
Virtually all modern washing machines monitor the water temperature during a wash, and if the temperature does not rise a certain amount within a pre-defined time then it should flag a fault. So, if the washing machine heater isn't working, then the program should abort and produce an error code (see Washing machine stops with an error code ).
However, much older washing machines controlled by mechanical programme timers didn't use any error codes and would just keep washing forever until the thermostat sensed the correct water temperature.
If the heater is faulty on a modern washing machine there should normally be an error code displayed that confirms the fault is with the heater circuit. On an older washing machine the symptoms should be that it carries on washing indefinitely and sticks on the wash cycle but other faults can cause this same symptom too.
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Testing a heating element
A heating element can easily be tested with a continuity meter and faulty ones are usually open circuit. Clearly the heater wiring should be checked first for any broken wires or dodgy connections. However, many washing machines now have the heater at the front and are as such a little inaccessible. You simply test a heating element with a continuity test meter. If it’s faulty it should be totally open circuit across the two main connections, or at least have a very high resistance. If it’s OK it should give a reading of somewhere in the range of 20 to 50 Ohms.
Heater protector device may have gone
If a heating element tests out ok and is not open circuit then if the wiring looks ok there could be a toc (thermal overload cut-out) that has gone open circuit. Sometimes such a small device could be located close to the heating element. However, some heaters will have a cut-out built into the heater or there may be a separate safety cut-out which is pushed inside a small tube on the heater. If this was the case it should be easy to spot. These devices should be simple fuse-like devices that are closed circuit when ok and open circuit when tripped. Never leave such a safety device by-passed. If one has gone open circuit you should be cautious as to why this happened because they should only trip if the heater got dangerously hot (energised with no water in the machine for example) but they could just go for no apparent reason.
No Error Code?
A few modern washing machines I've come across (such as Hotpoint and Zanussi) can develop faults that cause the washer to stick mid cycle and wash forever without producing an error code even though they are supposed to. Ironically it’s unlikely to be caused by the heater on machines designed to give error codes because they should easily detect a faulty heater and give the code. In such cases an engineer would be needed to sort it out. One suspect is the main programme PC but I distinctly remember changing more than one for this fault and it didn't cure it – unfortunately it could be hard to track the cause. It's certainly not a diy job.
Strictly speaking, if your washing machine completes a cycle on its own, in normal time, and especially if it's cleaning the laundry ok, then with the majority of washing machines the heater is probably working. Are you concerned that the heater isn't working because of poor wash results?
However, many washing machines have bugs in their software which allows certain faults to happen undetected.
An open circuit heater, or a bad connection on the heater on some modern Indesit and Hotpoint washing machines can have the bizarre effect of causing the washing machine to stop functioning apart from the lights and will not produce an error code. This is contrary to all logic. The lights come on, but nothing works. However, note that these symptoms can also be caused by other faults such as a faulty door interlock or on off switch or on even an open circuit motor or faulty PCB.
If the heating element goes open circuit mid-cycle some washers won’t trigger an error code and will stick on wash. Some may stick on the last minute of the wash cycle.
Zanussi anomalies: Certain Zanussi washing machines may not produce an error code yet still not heat the water up. If you suspect this is happening an engineer would be needed to diagnose the fault as it could also be a sensor or connection fault.
Experience of a Whitegoodshelp user: Bosch “Despite taking roughly the same amount of time to wash, and completing the cycle apparently normally, the heater on a Bosch washing machine did not appear to be coming on as confirmed by attaching an amp meter. This fault turned out to be a loose wire on the NTC sensor next to the heater” – see Bosch Wfr3267Gb/04 Not Heating (How to test an NTC thermistor)
Some Hotpoint washing machines: In the manual for models WMA30, WMA31, WMA32 & WMA33 it says, “If there is no detected rising water temperature over any continuous heating period of 10 mins, the microprocessor will advance to the next part of the program. The user may be unaware that a fault exists unless they use a high-temperature program, in which case the deterioration in wash performance may be noticed”. This of course could affect some other models too.
If the heater definitely isn't working
If the heater is definitely not working and an error code implicates the heater it should be a case of checking the connections. The heater's continuity can be checked with a meter and if it's open circuit or quite high resistance the heater will need replacing.
Where is the heater and how to replace it
See my article for more information – How to remove the heater from a washing machine