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Error code reference

Hotpoint Cooktop Error Code F18

Communication failure between VISUAL BOARD UART1 and EXTERNAL BOARD.

Hotpoint codesHotpoint cooktop codes

Communication failure between VISUAL BOARD UART1 and EXTERNAL BOARD.

First step from the service manual

Power off the appliance, wait 3 minutes and power it on.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F18 means on a Hotpoint cooktop

The F18 error code on a Hotpoint cooktop indicates a communication failure between the Visual Board's UART1 interface and the External Board. UART1 refers to a Universal Asynchronous Receiver-Transmitter port, which is a hardware serial communication channel used to pass data between the user-facing control board and the external power or relay board. When this data link is interrupted or fails to establish properly, the cooktop's control system detects the loss of communication and triggers the F18 fault to prevent unsafe or erratic operation.

This type of communication fault most commonly results from loose or damaged wiring harness connectors between the two boards, a corrupted signal caused by electrical interference, or a transient power supply issue that disrupted the data exchange during operation. In some cases, a firmware or microcontroller fault on either board can cause the UART1 channel to stop transmitting or receiving data correctly. Physical damage to the ribbon cable or connector pins, corrosion at the connector terminals, or a failed component on either the Visual Board or the External Board can also produce this fault.

Because communication faults are sometimes caused by temporary voltage fluctuations or software glitches, the first recommended diagnostic step is a full power cycle. Turning off the appliance, waiting at least 3 minutes to allow capacitors to discharge and the microcontrollers to fully reset, then restoring power will often clear transient faults. If the F18 code returns immediately after the reset, further inspection of the wiring, connectors, and boards themselves is required.

Source: manufacturer service documentation.

Common causes of F18

  1. 01

    Loose or disconnected wiring harness connector

    Wiring / connection

    The connector linking the Visual Board and the External Board may have worked loose due to vibration or handling. Inspect all harness connectors between the two boards for secure seating and signs of physical displacement.

  2. 02

    Transient power supply disruption

    Wiring / connection

    A momentary voltage spike or drop can interrupt the UART1 serial communication channel, triggering the fault without any permanent hardware damage. A 3-minute power cycle allows the boards to fully reset and often clears this type of fault.

  3. 03

    Corroded or damaged connector terminals

    Wiring / connection

    Moisture or heat exposure near the connector pins can cause corrosion or oxidation that degrades the signal integrity between boards. Look for discoloration, pitting, or residue on the terminal contacts.

  4. 04

    Failed Visual Board (UART1 port fault)

    Part replacement

    If the UART1 transmitter or receiver on the Visual Board has failed internally, communication cannot be established regardless of wiring condition. This typically requires board replacement to resolve.

  5. 05

    Failed External Board

    Part replacement

    A defective External Board that cannot receive or respond to UART1 signals will produce the same F18 communication fault. If the Visual Board tests correctly, the External Board should be evaluated for replacement.

See the test procedure for each cause

Frequently asked questions about F18

What does F18 mean on a Hotpoint cooktop?
F18 indicates a communication failure between the Visual Board's UART1 port and the External Board. These two boards exchange data continuously to coordinate control inputs and power output. When that communication link breaks down, the cooktop detects the fault and displays F18 to prevent unsafe operation. The cause can range from a loose connector to a failed circuit board.
Will resetting the cooktop clear the F18 error?
A power cycle reset is the first recommended step and will sometimes clear F18 if the fault was caused by a temporary power disruption or software glitch. Turn the cooktop off at the breaker or unplug it, wait at least 3 minutes, then restore power. If F18 returns immediately, the underlying hardware issue, such as a damaged connector or failed board, must be addressed before the fault will clear permanently.
Is it safe to use my Hotpoint cooktop while F18 is displayed?
No, you should not continue using the cooktop while F18 is active. A communication failure between the control boards means the appliance cannot reliably coordinate its control and power functions. Operating it in this state could result in unpredictable behavior. Turn the unit off and keep it off until the fault is diagnosed and resolved.
How do I fix the F18 error on a Hotpoint cooktop?
Start by powering the cooktop off and waiting 3 minutes before restoring power. If the error returns, the next step is to inspect the wiring harness and connectors between the Visual Board and the External Board for loose connections, damaged wires, or corroded terminals. If the wiring appears intact, one or both boards may need to be tested and potentially replaced. A qualified appliance technician can perform board-level diagnostics to identify which component is at fault.
How much does it cost to repair an F18 error on a Hotpoint cooktop?
Repair costs depend on the root cause. If the issue is simply a loose connector, the repair may only involve a service call fee, typically in the range of $75 to $150. If a control board needs to be replaced, total costs including parts and labor generally fall in the range of $150 to $400 or more, depending on the specific board required and local labor rates. Getting a diagnostic quote before authorizing repairs is recommended.

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