Fisher & Paykel Dishwasher Error Code U1

The U1 error code on a Fisher & Paykel dishwasher indicates a fill fault, specifically that the wash motor has failed to prime within the expected time window during the fill cycle. Priming occurs when the pump draws water up from the sump after the machine fills. If insufficient water is present in the sump, or if air is trapped in the system, the motor cannot develop the pressure needed to circulate water through the spray arms. The control board monitors this priming process and triggers U1 when the condition is not met within a set time limit.

Several conditions can prevent successful priming. The water supply valve may be closed or partially restricted, delivering too little water to the tub. The incoming water pressure may be below the minimum threshold: Fisher & Paykel specifies 50kPa as the minimum acceptable pressure. Machines configured for the HP (high pressure) programme will struggle or fail entirely on a low-pressure supply, and switching to the LP (low pressure) programme is the correct fix in that scenario. Siphoning through the drain hose, typically caused by an incorrectly routed or unlooped drain connection, can also evacuate water from the sump during filling.

Additional causes include a missing or improperly seated spray arm, which disrupts normal water circulation and prevents the motor from priming correctly. Excessive detergent foam can introduce enough air into the pump to cause a loss of prime. Finally, a failed fill valve that is stuck in the closed position will prevent water from entering the tub at all, and this component would need to be tested and replaced if found faulty.