When cooking is finished the fan usually continues for a period of time too cool oven down and then switch off. Now the oven fan stays on permanently after switching oven off and the only way too stop the fan is to switch cooker off at the mains.
This problem is caused by one of two components, depending on the model, there is a thermal cut in thermostat that keeps the fan running until the unit has cooled down and on some models there is a four wire timing device that keeps the fan running for a specific time after the temperature drops, the fault can only be casued by one of these components.
Smeg Service Engineer
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With a basic microwave there is a minimum of electronics and the fan starts when the oven is switched on and continues working until cooking has finished. In that case the fan is supplied from the timer and the circuit will be simple to check using a multimeter.
The more upmarket microwaves contain a great deal more electronics and the fan will continue to run after cooking has finished until the circuitry has cooled to a predetermined temperature.
In that case the the checking, fault location and rectification is probably completely beyond even most service engineers - who typically would simply replace circuit boards until the fault is cured...
Probably the cooling fan. There is a cabinet thermostat on most ovens these days (Especially wall or underbench models) to keep the cooling fan running after the cooking has finished and oven turned off. This fan will run for a few minutes to cool down the outside of the oven so it doesn't burn / discolour the surrounding cabinet or workbench. If the fan stays on all the time, I would say that the thermostat has probably jammed in the run or on position.
All microwaves do have a "transmitter" tube called a magnetron. It has to put electrical power into microwaves. To do so it gets warm or even hot. As soon as the transmitter is to hot, it must be cooled down. Most of the time it can be cooled without a fan. But as long as the thermostat indicates it is to hot, the system will cool. Even when you switched the system off. Don't unplug the microwave when it is still hot. It could damage the magnetron.
I would suspect that the problem is caused by the external cooling fan located under the outside cooker cabinet housing, which continues to operate as the oven is cooling down if it is built in, you will have to remove it from the oven housing to access the fan
Door needs to be closed in cook mode to work. You sure you put the switch in the right way up? Also you could have a dodgy door switch as the cook/cool switch and the door switch operate as a two-way circuit.
After grilling or cooking at higher temps leave the oven light on so the cooling fan continues to run for approx 1/4 hour, or whatever setting will keep the fan running...
1. Faulty thermostat. 2. Faulty thermal cut out switch. (controls power to cooling fan). 3. Faulty cooling fan (not fan inside oven).
Test thermostat by setting thermostat to low temperature like 60 oC. If oven gets much hotter then its a faulty thermostat. To test cooling fan and thermal switch take oven out and remove top or rear panels to expose components. When oven gets hot the cooling fan should turn on. If it doesn't then check to see if there is a mains voltage present. If mains current exist but fan is not turnig then replace fan. If mains voltage is not present then its the thermal switch.
1. Set the oven to the required temperature. 2. Press the g button. 3. Set the total cooking time with the + button (see the example in the illustration right, showing 1 hour and 30 minutes). 4. Press the h button. 5. Set the cooking finish time with the + button (the example in the illustration shows 12.30 hrs.). After setting the display shows the time of day and indicates »AUTO«. ❑ The oven cooling fan will start immediatley. ❑ At the pre-set time, the oven will be automatically switched ON. ❑ The settings can be corrected at any time. ❑ When the pre-set cooking finish time is reached, a signal sounds and the oven is automatically switched OFF. To turn the signal off, briefly press the h button. 6. Turn the oven selector switch to the 0 position. 7. The »AUTO« symbol blinks. Important: It must be switched OFF by pressing the E button.
Oven has power but switches don't turn on element or fan
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