# Range oven temperature drifting — running hotter or cooler as the range ages

> Range oven temperature drifting — running hotter or cooler as the range ages: symptoms, likely causes and how a technician diagnoses it. Very common AGA issue. Mon–Sun 8:00AM–8:00PM. Call or text 206-427-7323.

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

## 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

## What is usually behind it

- Oven thermostat out of calibration or failed (most common)
- Damaged door seal (common)
- Range not level (common and easily missed)
- Thermostat phial displaced from its spring clips (common after a previous repair)

## How a technician diagnoses it

1. Manual guidance: if turning the knob down has not worked or only worked briefly, a new thermostat is likely needed.
2. Check the door seal for damage.
3. Level 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.
4. Elise/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.
5. Thermostat 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.
6. After replacement, check correct operation before final reassembly and carry out earth bond and hi-pot electrical safety tests.

## Parts usually needed

- [Range oven thermostat (capillary/phial type)](https://aga.repair/aga-range-oven-thermostat-replacement) (control)
- [Range oven door seal / gasket](https://aga.repair/aga-range-door-seal-replacement) (seal)

## Appliances affected

- [AGA Elise](https://aga.repair/aga-elise-repair)
- [AGA Legacy](https://aga.repair/aga-legacy-repair)
- [AGA Mercury](https://aga.repair/aga-mercury-repair)
- [AGA Professional](https://aga.repair/aga-professional-repair)

> ⚠️ **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.

## Related AGA problems

- [Gas oven will not heat — bake ignitor glows but the gas valve never opens](https://aga.repair/aga-range-bake-ignitor-weak)
- [Range burner lights then goes out when the knob is released](https://aga.repair/aga-range-burner-wont-stay-lit)
- [Range cooktop burners will not spark, or spark continuously](https://aga.repair/aga-range-no-spark)

## 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.

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## Book a repair

- Call or text: 206-427-7323 (Mon–Sun 8:00AM–8:00PM, Pacific Time)
- Book online: https://aga.repair/contact/
- Email: service@aga.repair
- Service at your home across the Seattle–Tacoma metro, WA. Diagnostic fee applies toward your repair.

Independent service company — not affiliated with or authorized by AGA / AGA Rangemaster (Middleby). We repair out-of-warranty AGA appliances.