How do I prove the oven is running cool?

Use a standalone oven thermometer on the middle shelf. Set 180°C, give it a good twenty minutes beyond the point the ready light says it is up to heat, then read it. A consistent gap of 20°C or more is a thermostat that has drifted and is worth putting right.

Everything burns on top and stays raw underneath.

That is the signature of a fan that has stopped or slowed, so heat is no longer being circulated and the oven behaves like a conventional one with a hotspot. Check whether you can hear and see the fan turning; if not, it is a fan or fan motor job.

Is the door seal really worth replacing?

Yes, if it has gone. A leaking seal means the oven cycles continuously and never holds a steady temperature, which shows up as uneven cooking and higher running costs. Seals are a straightforward part and among the cheaper things to put right.

Can I just add 20 degrees to every recipe?

It gets dinner cooked, but it is not a fix. A drifting thermostat usually keeps drifting, the offset is rarely the same across the range, and an oven running cool has food safety implications for meat and reheated dishes. Have the thermostat tested rather than guessing at compensation.

Low risk

Updated 30 August 2026

Oven Burning Or Undercooking Food

The oven heats, but nothing cooks the way it should — cakes sink, tops burn while middles stay raw, and everything takes longer than the recipe.

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Appliance repair work, illustrative image

What's happening?

This is the fault people live with for years, because the oven works and only the results are wrong. Something is off between the temperature the dial asks for and the temperature the food actually sees. Thermostats drift as they age, so an oven set to 180°C may sit at 150°C or overshoot to 210°C, and the reading on the front tells you nothing about which. A fan oven that has lost its fan cooks like a conventional oven with a hotspot, browning the top and leaving the base underdone. A perished door seal bleeds heat continuously, so the oven cycles constantly and never settles. And a partly failed grill or top element in a multi-function oven can leave one heating source doing the work of two.

What usually causes it?

A drifted or failing thermostat, so the actual cavity temperature no longer matches the dial
A failed or slowing fan, turning a fan oven into an uneven conventional one
A perished, split or distorted door seal letting heat escape continuously
A door that no longer closes square, or hinges that have sagged over time
A partly failed element in a multi-function oven, so only one heat source is working
A displaced or missing fan baffle or rear cover, disrupting air circulation
Overcrowded shelves or foil on the base blocking airflow and radiant heat
A temperature sensor reading incorrectly on an electronically controlled oven

Is it dangerous?

Not in itself, but there is a food safety angle worth taking seriously. An oven running well below its setting means meat, poultry and reheated dishes may not reach a safe temperature even though the timings look right, which is a real risk rather than a culinary annoyance. If you suspect the oven is running cool, use a food thermometer on the food rather than trusting time. A hot smell of burning insulation or scorching around the door or controls is a different matter and a reason to stop using it.

Can I fix it myself?

Measure before you diagnose. Put a standalone oven thermometer on the middle shelf, set the oven to 180°C, let it run for twenty minutes past the point the light says it is up to temperature, and read it — that single test tells you whether the thermostat has drifted and by how much. Check the fan is turning and audible. Fold the door seal back and look for splits, hard spots and gaps, and do the paper test around the door. Take the foil off the oven floor and stop overcrowding shelves. Adjusting your settings to compensate is a workaround, not a repair.

When should you call an appliance repair engineer?

Call an appliance engineer when the thermometer shows a consistent offset, when the fan has stopped or slowed, or when the door seal needs replacing. It is worth doing rather than living with — a drifted thermostat wastes energy on every use and makes baking unpredictable. Call sooner if the oven overshoots badly, since an oven running much hotter than its setting is also the condition that trips thermal cut-outs.

What will the appliance repair engineer actually do?

Measure actual cavity temperature against the setting with a calibrated probe, at more than one point
Test the thermostat or temperature sensor and check the control board's response
Check fan operation and speed, and the baffle and rear cover positions that direct airflow
Test each element and function separately to find a partly failed heat source
Inspect and replace the door seal, and adjust or replace sagging hinges so the door closes square
Recalibrate or replace the thermostat or sensor, then verify the oven holds temperature across the range

Frequently asked questions

We’re happy to answer all your questions.

Sources & References

Electric Oven Not Heating UpCaution Dishwasher Not Draining Or Leaving Dishes DirtyLow risk Burnt-On Grease Inside The OvenCaution

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