Cooling fan always running

This step-by-step repair guide walks you through fixing cooling fan always running on your Bosch HII8057U (Induction Range). With the right tools and parts, most homeowners can complete this repair in 1–2 hours and avoid a costly service call.

Part of our Top 20 Oven Models & Common Repair Issues Guide. Browse all oven repair guides for related models and issues.

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Common Symptoms & Causes

If your Bosch HII8057U is experiencing a cooling fan that won’t shut off, you may notice one or more of the following signs:

The cooling fan continues running 30+ minutes after the cooktop has been turned off
The fan runs at full speed even when no burners have been recently used
The control panel feels cool to the touch while the fan still operates
The fan cycles on immediately at startup before any cooking begins

This issue is most commonly caused by a faulty temperature sensor or a failing control board that is incorrectly reading residual heat levels, preventing the fan relay from signaling a proper shutdown.

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Safety First

Unplug the oven from the power outlet before starting any repair — never work on a live appliance.
Wear work gloves when handling metal brackets, sheet metal edges, or sharp components.
Take photos with your phone before disconnecting any wiring harnesses or connectors.
Work in a well-lit area with enough floor space to lay removed panels flat.

Tools & Parts Needed

Essential Tools

Phillips #2 screwdriver
¼” nut driver
Multimeter
Work gloves (heat-rated)
Flashlight

Replacement Parts

Step-by-Step Repair Instructions

Step 1

The cooling fan on this induction range is designed to run during and after cooking to dissipate residual heat from the induction electronics, so operation for up to 30 minutes after shutoff is completely normal. If the fan is still running more than an hour after the range has been off and fully cooled, the fan relay on the control board is likely stuck in the closed position, meaning it is continuously supplying power to the fan motor regardless of actual temperature. This distinction matters before you start disassembling anything — confirm the range has genuinely been off and idle for over an hour before diagnosing a fault.

Step 2

Unplug the range from the wall outlet before opening any panels — induction ranges store high-voltage charge in capacitors, so wait at least 5 minutes after unplugging before touching internal components. Remove the rear access panel (4 quarter-inch hex screws) to reach the fan and control board, then isolate the fan motor by disconnecting it from the board and applying 120V directly to the motor terminals using a short test lead. If the motor runs smoothly on direct power, the motor itself is healthy and the fault lies upstream with the control board relay that is stuck closed.

Step 3

Locate the fan relay on the control board PCB — it is typically labeled or identifiable by the fan circuit trace, and your service manual or a PCB diagram will confirm the exact component. Visually inspect the relay for signs of heat damage such as burn marks, discoloration, or a cracked housing, and use a multimeter in continuity mode to check whether the relay contacts are stuck closed when the board is unpowered (they should show open). A stuck-closed relay confirms the control board is the root cause and needs to be replaced, since individual relay replacement requires soldering and is generally not cost-effective on this model.

Step 4

If the fan is not only running continuously but also producing grinding, rattling, or bearing noise, the fan motor itself has a separate mechanical failure in addition to — or possibly contributing to — the continuous-run symptom. Address the noisy fan motor first by removing the 2 Phillips screws securing it and disconnecting the wiring harness, then replace with an exact OEM part to ensure correct airflow volume for the induction electronics. Pro tip: a failing motor drawing excess current can sometimes cause relay stress over time, so replacing a noisy motor early may protect the control board.

Step 5

Before unplugging any connectors from the control board, photograph every connector and its orientation — these boards often have multiple similarly sized harnesses and incorrect reconnection can cause new faults or damage. Replace the control board with the correct OEM part for the HII8057U, as the relay voltage ratings and firmware are specific to this model. Route all harnesses back exactly as photographed, ensuring no wires are pinched by the panel when you reinstall it.

Step 6

Restore power and run a short induction cooking cycle, then shut the range off and observe fan behavior. The fan should run actively during cooking and continue for a period afterward as the electronics cool, then shut off completely — continuous running after full cooldown confirms the repair was unsuccessful and the board replacement should be revisited. If the fan now shuts off correctly, the repair is complete; log the fix and the board part number for future reference.

Where to Buy Replacement Parts

Find genuine OEM and aftermarket replacement parts for your Bosch HII8057U (Induction Range) on Amazon:

When to Call a Professional

If the issue persists after completing all steps above, the problem may involve the sealed refrigerant system, a failed main control board, or wiring that requires specialized diagnostic equipment. Contact a licensed appliance technician — attempting sealed-system repairs without EPA 608 certification is illegal and unsafe.

How Much Does This Repair Cost?

DIY replacement parts for this repair, such as a new control board or temperature sensor, typically cost between $20 and $120. A professional service call will generally run $150–$300 once you factor in labor and diagnostic fees. Tackling this repair yourself can save you $100 or more.

Frequently Asked Questions

Is it normal for the cooling fan on my Bosch HII8057U to run after I finish cooking?

Yes, the cooling fan typically runs for a short time after use to dissipate residual heat. However, if it runs continuously without stopping, that indicates a fault that needs attention.

Could a faulty temperature sensor cause the cooling fan to run constantly?

Yes, a defective temperature sensor can send incorrect readings to the control board, causing the fan to run indefinitely. Testing and replacing the sensor often resolves the issue.

Do I need to replace the control board if the cooling fan won’t stop running?

Not necessarily — rule out the temperature sensor and wiring connections first before replacing the control board. Board replacement is typically a last resort after other components are tested.

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