# AGA thermocouple open circuit or drifting

> AGA thermocouple open circuit or drifting: symptoms, likely causes and how a technician diagnoses it. Common AGA issue. Mon–Sun 8:00AM–8:00PM. Call or text 206-427-7323.

Common issue — here is how we diagnose it, which parts are usually involved, and when to call a pro.

**Common** · Professional repair only

## What you will notice

- Zone overheats or never reaches temperature
- Error 020–024 or 060–100
- Zone locks out intermittently
- Two thermocouples in one zone report very different temperatures

## What is usually behind it

- Thermocouple open circuit (most common)
- Thermocouple that tests OK cold but drifts or opens at operating temperature (common and easily missed)
- Thermocouple not fully plugged into the user control panel (common)
- Thermocouples cross-connected on the back of the TCU (causes overheat code 120–124) (installation/repair error)

## How a technician diagnoses it

1. Duplex thermocouples: 4 wires at the plug. Each thermocouple is one green + one white conductor — measure across green and white.
2. Do NOT clear a thermocouple on a cold bench test alone. Units have tested fine at room temperature and gone open circuit hot.
3. Verify the tip is located correctly in its bracket on the element; on the hotplates the thermocouple attaches to the element with a bracket.
4. Confirm the TCU rear connections match the imprinted zone abbreviations: BO, HS, SS, SO, RO.
5. Refit the rubber bungs in the thermocouple conduits after replacement — missing bungs cause user-panel overheat (code 139).

## Parts usually needed

- [AGA duplex thermocouple (eR7 platform)](https://aga.repair/aga-thermocouple-replacement) (sensor)
- [AGA thermocouple conduit sealing bung / plug](https://aga.repair/aga-conduit-bung-replacement) (seal)

## Related error codes

- [020-024 — Thermocouple differential — the two thermocouples in a zone disagree](https://aga.repair/aga-error-code-020-024)
- [060-100 — Thermocouple open circuit](https://aga.repair/aga-error-code-060-100)
- [120-124 — Cooking zone overheat error](https://aga.repair/aga-error-code-120-124)

## Appliances affected

- [AGA Classic eR7](https://aga.repair/aga-classic-er7-repair)
- [AGA Classic R7](https://aga.repair/aga-classic-r7-repair)
- [AGA Classic 39" Total Control](https://aga.repair/aga-classic-total-control-repair)
- [AGA ERA](https://aga.repair/aga-era-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

- [AGA oven door rope seal worn — heat loss, poor cooking, hot fascia](https://aga.repair/aga-door-rope-seal)
- [AGA oven or hotplate element failed (no heat / reduced heat)](https://aga.repair/aga-element-open)
- [AGA full power time-out (codes 010–014) — zone too slow to reach temperature](https://aga.repair/aga-full-power-timeout)

## 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.