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Error code reference

Ariston Dishwasher Error Code AL 99

Communication not possible

Ariston codesAriston dishwasher codes

Communication not possible - serial communication failure between Bit100 timer and interface card.

First step from the service manual

Check cables on serial connector; verify motor and timer connections are not disconnected or inverted; check auxiliary starter wash motor.

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

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What AL 99 means on a Ariston dishwasher

AL 99 on an Ariston dishwasher indicates a serial communication failure between the Bit100 timer module and the interface card. These two control components rely on a serial data connection to coordinate machine operations, including cycle sequencing, motor control, and user interface feedback. When this communication link breaks down or produces signals the receiving board cannot interpret, the dishwasher halts operation and logs the AL 99 fault.

The most common physical causes involve the serial connector and its associated wiring harness. Cables that have become loose, corroded, or improperly seated on the serial connector will interrupt data transmission. Connections that are inverted, meaning a connector plugged in backwards or a wire routed to the wrong pin, can also prevent communication entirely. The wash motor and its starter circuit are also part of the diagnostic scope, as a fault in the auxiliary starter wash motor can disrupt the signals flowing between the timer and interface card.

Diagnosing AL 99 begins with a thorough physical inspection of all cables connected to the serial interface between the Bit100 timer and the interface card. Technicians should confirm that no connectors are unplugged, reversed, or showing signs of corrosion or heat damage. If the wiring checks out, attention shifts to the auxiliary starter wash motor, which should be tested for proper function. If both wiring and the motor are intact, either the Bit100 timer or the interface card itself may have failed internally and require replacement.

Source: manufacturer service documentation.

Common causes of AL 99

  1. 01

    Loose or disconnected serial connector cable

    Wiring / connection

    The cable linking the Bit100 timer to the interface card may have worked loose over time due to vibration. Inspect the serial connector on both boards for secure seating.

  2. 02

    Inverted or incorrectly routed connector

    Wiring / connection

    A connector plugged in backwards or a wire installed on the wrong pin will prevent serial communication entirely. Check that all connectors match their correct orientation on both the timer and interface card.

  3. 03

    Auxiliary starter wash motor fault

    Part replacement

    A failure in the auxiliary starter wash motor can interfere with signals between the timer and interface card. Test the motor for continuity and proper operation as part of the diagnostic process.

  4. 04

    Damaged or corroded wiring harness

    Part replacement

    Wires in the harness connecting the two control boards can suffer from corrosion, pinching, or heat damage, breaking the serial data path. A visual inspection along the full length of the harness can reveal damage.

  5. 05

    Failed Bit100 timer or interface card

    Part replacement

    If all wiring and the motor check out correctly, one of the two control boards may have an internal failure preventing communication. Replacing the faulty board is typically required in this scenario.

See the test procedure for each cause

Frequently asked questions about AL 99

What does AL 99 mean on a Ariston dishwasher?
AL 99 signals a serial communication failure between the Bit100 timer module and the interface card. These two control boards must exchange data continuously for the dishwasher to operate. When that communication link is broken or disrupted, the machine stops and displays AL 99. The fault is typically caused by a loose cable, an inverted connector, or a problem with the auxiliary starter wash motor.
How do I fix the AL 99 error on my Ariston dishwasher?
Start by inspecting all cables connected to the serial connector between the Bit100 timer and the interface card, ensuring none are loose, disconnected, or plugged in backwards. Also confirm that the motor and timer connections are secure and correctly oriented. If the wiring is intact, test the auxiliary starter wash motor for proper function. If these steps do not resolve the fault, one of the control boards may need to be replaced by a qualified technician.
Is it safe to use my Ariston dishwasher when AL 99 is displayed?
No, you should not attempt to run the dishwasher while AL 99 is active. The error indicates that critical control components cannot communicate, meaning the machine cannot manage its cycle correctly or safely. Running it in this condition risks improper operation or potential component damage. The fault should be diagnosed and resolved before resuming normal use.
Will resetting my Ariston dishwasher clear the AL 99 error?
A reset may temporarily clear the error code, but if the underlying cause is a physical wiring issue, an inverted connector, or a faulty motor or control board, the fault will return when the machine attempts to operate. A reset is not a repair. The serial communication problem must be identified and corrected to permanently resolve AL 99.
How much does it cost to repair an AL 99 error on an Ariston dishwasher?
Repair costs vary depending on the cause. If the issue is simply a loose or incorrectly seated connector, a service call to inspect and reseat the wiring could cost between $75 and $150. If the auxiliary starter wash motor requires replacement, parts and labor typically range from $100 to $250. Replacing a failed Bit100 timer or interface card can push the total cost to between $150 and $400 or more, depending on parts availability and local labor rates.

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