Why does a fisher and paykel DD-603 randomly gives f1 code even when not in use

F1 is the code for a water flood in the machine and can appear at any time the machine is plugged in to the power, it does not have to be "on" for F1 to appear. F1 is activated by water causing an electrical bridge between 2 probes on the circuit board on the bottom tray of the machine. (you have to remove the lower drawer to find this card, it is under a protective plastic cover). BEWARE - this circuit card has mains voltage on it whenever the machine is plugged into the power so make sure the power lead is disconnected from the wall plug before you start dismantling.
The likely cause of your problem is:
1. Water is still in the base of the machine from an earlier flood situation - remove the bottom drawer and check, if it's even slightly wet, dry it out really well. A hair dryer is useful here once you have mopped up as much water as you can with cloths. Blow the hot air under the circuit card. If water re-appears after that, you have a leak somewhere so find it and fix it and dry it out again.
2. Water has corroded this circuit card and the 2 probes are connected together by this corrosion - with the mains power disconnected, remove the plastic cover and remove the card, have a look at the underside of the circuit card, check the surface is clean, dry and corrosion free. Cleaning it with an old toothbrush and isopropyl alcohol, blow it dry with compressed air or a hair dryer is very effective.
3. Flood water has damaged the circuit card - if you see signs of burns, scorching, etc when you remove the circuit card for inspection especially on the underside of the card, the card may need to be replaced.

Dishdrawers are particularly vulnerable to water floods damaging this circuit card - a very silly place to install a card with mains voltages on it in the base of the machine where any water leaks will collect. A very common cause of water flooding are dishes, utensils in the machine that extend above the top rim of the drawer. Even slightly above will prevent the drawer lid from effectively sealing with the drawer and water will splash out when the machine operates and flood it.

Fault code F1 can come from a number of different sources and can remain on as long as the machine has power (does not need to be operating). Once a fault is repaired it can be cleared by pressing the Power button. If the fault is still present then it will not
clear. The service manual says: The faults are displayed in the LCD as one of 5 F (fatal) faults or 1 U (user) fault along with the symbol of a spanner. A fatal fault will usually require the assistance of a qualified service person...

Fault Code Description:
Fault Code: F1
LED Display: Rinse LED
Fault: The flood switch has been activated for more than six seconds
Possible Causes
_ Inlet hose to inlet valve connection loose
_ Inlet valve body leak
_ Damage to the fill or drain hoses
_ Heater plate damage (chipped enamel)
_ Seals/O Rings (pinched, contaminated or poor join)
_ Dispenser (seal, diverter valve or weld leak)
_ Lid area (lid motors not functioning correctly, lid off yoke or foreign object interfering with lid seal)

Fault Code Problem Solving:

1.Question: Is there a F1 on both displays? Yes: Go to Question 2. No: If power fails to the bottom tub it will cause thetop tub to go F1. Test heater plate.
2.Question: Has a flood occurred? (N.B. The flood may have dried up) Yes: Go to Question 3. No: Go to Question 13
3.Is the lid sealing on the tub correctly? Yes: Go to Question 5. No: Go to Question 4
4.Question: Are the lid actuators functioning correctly? Yes: Go to Question 5. No: Check the lid actuators are assembled correctly on the slides and yokes. Check the plugs on the RFI board and the terminals on the lid motors. If the lid actuators look slow replace them.
5.Question: Is the water level in the tub high? Yes: Go to Question 6. No: Go to Question 8
6.Question: Is the water inlet valve leaking? Yes: Replace inlet valve. No: Go to Question 7
7.Question: Is the DishDrawer priming correctly? Yes: Go to Question 12. Go to Question 8
8.Question: Is the spray arm split? Yes: Replace spray arm. No: Go to Question 9
9.Question: Is the spray arm running freely? Yes: Go to Question 10. No: Check the rotor is running freely, clear of foreign objects and fitted correctly. Make sure the wash impeller is not slipping off the rotor shaft.
10.Question: Is water leaking from a split inlet or drain hose? Yes: Replace split inlet or drain hose. No: Go to Question 11
11.Question: Is water leaking around the heater plate 'O' rings? Yes: Replace or refit 'O' rings. No: Go to Question 12
12.Question: Is the drain hose blocked? Yes: Clear drain hose of blockage. No:Go to Question 13
13.Question: Is there condensation or foreign matter around the flood switch PCB? Yes: Clear flood sensor of condensation or foreign matter. No: Go to Question 14
14.After clearing water does the F1 fault code still activate? Yes: Replace Chassis RFI board. No: Go to Question 15
15.Refer to Bulletin DW028 DW025, 028, 031, 040