In an electric fan oven when cooking a specific recipe at a given temperature should that oven reach that temperature given the 20deg. difference between that and a conventional oven? I bought an oven thermometer placed it in the Fan oven and set the oven at 170deg C. the thermometer only reached 140deg. C. is my oven faulty?

3 Answers 3


So now you have the oven thermostat saying one thing and a thermometer saying something else. As other answers have said, that could be because you didn't wait long enough for the oven to heat evenly, or that the thermometer is not in a good location. If neither of those applies, the only conclusion you can draw is that one of them is wrong. In order to conclude that the oven is off, you need at least two thermometers. Of course, if you do that, you may find that all three disagree.


Yes, it sounds like your oven is faulty. Or at least that the thermostat is wildly off. It's not uncommon for thermostats to be 10-20°C off, but 30°C seems like too much.

(On the other hand, how much do you trust your thermometer?)

  • There's also a good chance that the oven temperature sensor is in a location that is not ideal for determining the true temperature of the oven. Perhaps the sensor is in sheltered area which gets hotter than the rest of the oven, or is not positioned roughly in the middle of the oven.
    – bob1
    Feb 26, 2019 at 22:34
  • I have frequently enough seen ovens to go 30 and even 40 Celsius off. It is a common thing, and I don't know if a manufacturer would accept a claim of "faulty" when it happens, but it is something many people live with without a problem.
    – rumtscho
    Feb 27, 2019 at 18:21

You also have to consider how long the oven had to warm up (when the light goes off it may not be evenly warmed up, though this should be better in a fan oven) and whether you had to open the door an let cold air in to read the thermometer.

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