What FB Means
WHICH MACHINES THIS APPLIES TO: FB is listed in both the DW20 and the DW70 fault tables. The DW90 platform numbers the same fault F:45, and the current DBI, DFI and DSD machines call it a diverter fault under F45.
DW20 AND DW70 PLATFORM - WHAT FB MEANS: the service manual reads "Spray arm divider fault. Position contact is continuously closed or open. The programme proceeds. Indication only in the service menu." The divider, or diverter, is the valve that sends the pumped water to the upper spray arm or the lower one in turn. A position contact tells the control where it has got to. If that contact never changes state - stuck closed or stuck open - the control cannot tell which way the water is going.
WHAT THE MACHINE DOES NEXT: it carries on regardless. The manual is explicit that the programme proceeds and the indication is in the service menu only. On a DW70.4, which shows faults as text rather than codes, the same condition appears as "Diverter fault". The symptom that reaches the owner is uneven washing - one basket consistently cleaner than the other, or the top rack coming out with food still on it while the bottom is fine.
CLASSIFICATION: fault. Nothing is unsafe, but the wash is only reaching half of what it should.
Common Causes of FB
- Position contact on the divider stuck closed or open
- Divider gearbox worn or jammed
- Wiring or connector to the position contact damaged
- Control unit not reading the contact
🔧 One Safe Check You Can Try
Before assuming the diverter, rule out the things that produce the same symptom and are genuinely in the owner's hands. Switch the machine off at the outlet or the breaker and let it cool, then check that both spray arms turn freely by hand and that their jets are clear - hold each arm up to the light and look through the holes, because scale and seeds block them from the inside. Check that nothing in the upper basket is hanging down far enough to stop the arm turning, which is the most common cause of a clean bottom and a dirty top. Clean the filters while the machine is off. If the arms spin freely, the jets are clear, nothing is fouling them and one level is still not being washed, the divider and its position contact are the remaining explanation and that is a technician's job: the gearbox and contacts sit under the tub.
⚠ Why You Shouldn't Go Further Than That
- The divider, its gearbox and its contacts are under the wash tub, reachable only with the dishwasher isolated from power and drawn out of the cabinet.
- The contact wiring runs with the pump supply in the base, which is live whenever the machine is connected to power.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.