Range oven temperature drifting — running hotter or cooler as the range ages
Very common issue — here is how we diagnose it, which parts are usually involved, and when to call a pro.
- Very common
- Professional repair only
- Pro Range
Symptoms
What you will notice
- Food burning or undercooking
- Oven getting hotter as the range gets older
- Turning the knob down helps only briefly
- Uneven baking
Likely causes
What is usually behind it
- Oven thermostat out of calibration or failedmost common
- Damaged door sealcommon
- Range not levelcommon and easily missed
- Thermostat phial displaced from its spring clipscommon after a previous repair
Diagnostics
How a technician diagnoses it
Our technicians follow the factory diagnostic path for this fault.
- 1Manual guidance: if turning the knob down has not worked or only worked briefly, a new thermostat is likely needed.
- 2Check the door seal for damage.
- 3Level test: a dish of water on the shelf should be the same depth all over. If deeper at the back, the range needs raising at the back or lowering at the front.
- 4Elise/Mercury 48": there are TWO oven thermostats, both located under the gas hotplate. The LH oven thermostat is removed from the rear of the appliance; the RH oven thermostat is removed from the top of the RH oven.
- 5Thermostat replacement requires removing the fascia and the gas hotplate assembly. The phial sits inside the oven cavity behind the oven fan baffle plate, held by two spring clips; remove the four baffle-plate screws to reach it.
- 6After replacement, check correct operation before final reassembly and carry out earth bond and hi-pot electrical safety tests.
Safety & DIY disclaimer
Guides on this site are for information only. Appliance repair involves 240V electricity, gas connections, refrigerant and heavy cast-iron parts — anything you do yourself is at your own risk and can damage the appliance or cause injury. The safe option is to book a qualified technician.
Parts
Parts usually needed
We confirm the failing part with diagnostics before replacing anything.
Coverage
Appliances affected
Keep reading
Related AGA problems
Frequently asked questions
Can I fix this myself?
Professional repair only. This fault involves gas or 240V electrical components — diagnosis and repair should be done by a licensed technician.
How much does it cost to fix this issue?
Every visit starts with diagnostics and a written estimate — the diagnostic fee applies toward your repair when you proceed. We never start work without your approval.
Not sure? We diagnose first.
Book a diagnostic visit — you get a written estimate before any work, and the diagnostic fee applies toward your repair.
Mon–Sun 8:00AM–8:00PM
Independent service company — not affiliated with or authorized by AGA / AGA Rangemaster (Middleby). We repair out-of-warranty AGA appliances.