Stop right now. Before you finish reading this introduction, go to your consumer unit and switch off the circuit breaker that supplies the induction hob. Done? That simple step could have prevented a dangerous short circuit or an electric shock. Now let's understand what is happening and how to fix it permanently.
A professional diagnostic call‑out can easily cost a significant amount, yet the faulty component might be a tiny NTC thermistor that costs only a few pounds. This guide walks you through the diagnosis and repair so you can decide whether to tackle it yourself or call in a specialist.
How the Induction Hob Works – and Why It Fails
Induction hobs use electromagnetic induction to heat cookware directly. Beneath the ceramic glass surface, copper induction coils generate a high‑frequency alternating magnetic field. A power board (also called an inverter board) converts mains AC into high‑frequency AC for these coils. The power board contains Insulated Gate Bipolar Transistors (IGBTs) and high‑capacitance capacitors. A control board manages user input, displays error codes, and communicates with the power board. NTC thermistors (temperature sensors) are located under each cooking zone to prevent overheating. A pot detection circuit senses whether a ferromagnetic pan is present.
Common failure modes include: blown IGBTs due to overheating or power surges; degraded capacitors on the power board; NTC thermistors that drift out of specification; failed cooling fans; and loose terminal block connections. The ‘F’ error typically indicates a fault that the control board has detected, such as overheating, a sensor failure, or a communication error between boards.
Quick Diagnosis Table
| Symptom | Likely Fault | First Action |
|---|---|---|
| Flashing ‘F’, no heating at all | Power board failure (IGBTs, capacitors) or control board communication error | Check circuit breaker, then inspect power board for burnt components |
| ‘F’ error only on one cooking zone | Faulty NTC thermistor or induction coil on that zone | Test thermistor resistance; check coil continuity |
| ‘F’ error after using multiple high‑power zones | Power management limiting current, not a fault | Allow hob to cool; test with single zone |
| ‘F’ error accompanied by no fan noise | Cooling fan failure causing overheating | Check fan operation; clean or replace |
Estimated Cost of Common Replacement Parts
| Material / Part | Estimated Price Range | Where to Find |
|---|---|---|
| NTC thermistor | £5 – £15 | Online electronics retailers, spare parts shops |
| Induction coil | £20 – £50 | Appliance spare parts websites, specialist stores |
| Power board (inverter board) | £50 – £150 | Online spares suppliers, manufacturer aftermarket |
| Control board | £30 – £80 | Online appliance parts, eBay (used) |
| Cooling fan | £10 – £25 | Online electronics, computer fan retailers |
Tools and Materials You Will Need
- Multimeter (able to measure voltage, continuity, and resistance)
- Screwdriver set (Phillips, flathead, Torx)
- Pliers (for gripping and manipulating wires)
- Wire strippers / cutters (if wiring repairs are required)
- Insulated tools (for working near electrical components)
- Thermal paste (if replacing components that require heat dissipation)
- Padded work surface (e.g., blanket, cardboard)
Step‑by‑Step Repair Guide
Before you begin: read each step fully. Some stages require a multimeter – if you do not have one or are unsure how to use it safely, stop and consider calling a professional.
Step 1 – Safety and Power Isolation
- Ensure the circuit breaker at the consumer unit is switched off. Use your multimeter to verify zero voltage at the hob’s terminal block.
- Wait at least 10 minutes for internal capacitors to discharge passively through bleed resistors. For complete safety, manually discharge large capacitors using a suitable tool – but only if you are trained to do so.
- Wear insulated gloves and safety glasses.
Step 2 – Gain Access to the Hob’s Internals
- Remove the hob from the worktop. Most models are held in place by clips or brackets. Lift the hob gently and place it ceramic‑glass‑side down on a padded surface.
- Remove the perimeter screws that hold the metal casing or the glass top. Carefully lift the glass top to expose the internal components: induction coils, power board, control board, and fan.
- You probably think the next move is to start testing electronic parts… but the smartest approach is to begin with the simplest checks.
Step 3 – Simple Checks First
- Pan suitability and placement: Ensure you are using a ferromagnetic pan (test with a magnet). The hob’s pot detection system requires a specific pan diameter and material.
- Ventilation: Check that the ventilation openings are clear. There should be at least 5 mm to 20 mm clearance beneath the hob for airflow. A blocked vent can cause overheating and trigger the ‘F’ error.
- Loose connections: Inspect the terminal block – tighten any screws if they feel loose. Loose connections can cause arcing and localised melting.
Step 4 – Test the NTC Thermistors
- Locate the NTC thermistors under each cooking zone (they look like small glass beads or disc‑shaped components with two wires).
- Use your multimeter in resistance mode. Measure the thermistor’s resistance. A typical value at room temperature is around 1 kΩ to 50 kΩ, depending on the model. (Exact specifications are not provided here – if available, compare with manufacturer data.)
- If the reading is outside the expected range (e.g., open circuit or near zero), the thermistor is faulty and should be replaced.
This test requires a multimeter. If you do not have one, stop here. Difficulty: Medium.
Step 5 – Test the Induction Coils
- Each cooking zone has a copper induction coil. Unplug the coil’s connector from the power board.
- Measure the coil’s resistance with the multimeter. A healthy coil will show a very low resistance – typically between 0.2 Ω and 1.5 Ω. An open circuit (infinite resistance) indicates a broken coil winding.
- If the coil is faulty, you will need to replace it. This is uncommon but possible.
Step 6 – Inspect the Power Board
- Look for obvious signs of damage: burnt areas, charred resistors, swollen or leaking capacitors, or cracked solder joints. Also check the IGBT modules (usually large black rectangular components mounted on a heatsink).
- If you see any of these signs, the entire power board may need replacement. Testing individual components (IGBTs, capacitors) is possible but requires specialised knowledge and equipment.
Step 7 – Replace Faulty Components
- If a specific part (NTC thermistor, cooling fan, induction coil) is identified as defective, order the correct replacement for your hob model. Be careful with wiring polarity if applicable.
- When replacing a power board or control board, unplug all connectors and remove the mounting screws. Apply fresh thermal paste to the heatsink if required. Install the new board and reconnect everything.
Step 8 – Reassemble and Test
- Carefully replace the glass top, ensuring no wires are pinched. Secure all screws. Mount the hob back into the worktop without fully tightening – leave it loose so you can remove it again if needed.
- Restore power at the consumer unit. Test the hob with a suitable pan. If the ‘F’ error is gone and the hob heats normally, tighten the worktop fixings fully.
- If the error persists, re‑check all connections or consider that the control board may be faulty. Replacing a control board is a similar process.
Time to Call a Professional?
Self‑Assessment Questions
- Do you own a multimeter and know how to measure resistance and continuity?
- Have you ever worked inside an appliance with live voltage? Do you understand capacitor discharge safety?
- Are you comfortable disconnecting and reconnecting internal wiring – and correctly identifying components?
If you answered no to any of these, calling a qualified appliance repair technician is the right decision – no shame. The cost of a service call is far less than the risk of electric shock or damaging the hob further.
Curiosity & Data
Based on standard engineering principles and field observations, a large fraction of induction hob failures are caused by simple issues: blocked ventilation, a faulty thermistor, or a loose terminal. These problems can be fixed for under £20 and often take less than an hour once diagnosed. Yet many households scrap a perfectly repairable hob and buy a new one – a costly and wasteful habit. With a little knowledge, you can keep your appliance running for years longer.
⚠️ This guide is intended for reference only. The user assumes full responsibility for any repair undertaken. When in doubt about any step or safety requirement, seek assistance from a qualified professional. Electricity can kill – proceed only if you are confident in your abilities.
Conclusion – Should You Repair or Replace?
Consider the age and overall condition of your hob. If it is more than 10 years old and the required repair involves a costly power board replacement, it may be more economical to invest in a new model. On the other hand, if the fix is simple (e.g., a £10 thermistor or a cleaning of ventilation slots), go ahead and repair.
If you managed to fix the hob yourself, congratulations – you have saved money and reduced electronic waste. If you chose to call a professional, that is equally valid: the important thing is that the problem is solved safely. Either way, you now understand the system far better than before.
FAQ
What does the ‘F’ error mean on an induction hob?
The ‘F’ error is a generic fault code indicating that the hob’s control board has detected a problem. Common causes include power board failure, a defective NTC thermistor, overheating due to blocked ventilation, or a communication error between boards.
Can I fix the hob if the power board has visible burnt components?
Replacing a burnt power board is possible, but you must first identify and correct the cause (e.g., a failed fan or a power surge). Board replacement is a medium‑difficulty job requiring careful disassembly and reconnection. If the board is severely damaged, replacement of the entire board is usually the most practical solution.
How much does a new NTC thermistor cost?
An NTC thermistor for an induction hob typically costs between £5 and £15. It is a small component that can be replaced with basic soldering skills or by plugging in a matching replacement.
When should I call a professional instead of attempting the repair?
Call a professional if you do not own a multimeter, are unsure how to safely discharge capacitors, or feel uncomfortable working with mains electricity. Also, if the hob is still under warranty, any intervention may void it – in that case, let an authorised technician handle it.
