Any help with this problem appreciated:

My DW920 (2006 vintage) shows U1 error. I have the user manual and exploded parts diagrams. U1 means "failed to fill with water to correct level". Machine previously worked ok, not moved or any other change. I checked obvious things eg tap on. A slight trickle of water would enter machine. After a minute or so, machine would pump water out and try to fill again. After second try failed, U1 error appeared. I replaced the water inlet valve - a common problem, I gather - with a compatible 4L/m valve instead of original 5L/m. Also replaced the white plastic push button tray (part 696040177), as it was cracked.

Now good flow of water runs into machine in first minute, then water stops. No other machine action evident. Then machine pumps out, tries to fill again, then U1 error. I tried adding 3L of water manually to the tub during first minute - had no effect. It seems the controller board is at least partly working - attempts initial water fill and pump out.

I gather this machine does not have a water level sensor. Apparently the machine senses water present from the current in the wash pump, which is erratic until enough water is pumping. Apparently current should settle down in first minute.

I'm puzzled that I seem to have two problems, each of which causes U1 error - seems unlikely. I'm an amateur at dishwashers. But my thinking is that problem now might be: faulty controller - no signal to wash pump; or faulty connection from controller to wash pump; or faulty wash pump. Or maybe faulty starter capacitor - stops wash motor from starting?

If it is pump or controller, I don't know whether new parts cost would be justified for a 6 yr old machine with a poor reputation (I gather). But I'd like to investigate problem further, in case there is a low cost fix. I have a multimeter.

Any suggestions?

Don, September 2012

And 11 years later, this fixed my almost new (ie hardly used) F&P Nautilus that had sat in storage for 20 years. Thank you. Storage without use must have been enough to dry the start capacitor out, and it failed.

I have something to add to the U1 and F1 errors too. If you get an F1 fault and the flooding is minor and slow, it will most probably be a small leak in the door seal which is dripping into the base, and will eventually set off the flood sensor. You might only end up with a small amount of water on the floor.

If the wash motor start capacitor fails, the machine will overfill with water because it doesn't get an "I'm full" signal from the pump motor. This will lead to a fair bit more water on the floor, as it isn't just a drip from a leaky seal, it's a fair bit of flow from the machine overfilling and the overflow leaking out of the holes near the door hinges. Lots more flow, so even though the flood sensor activates, there's lot's more water to flood.

I hope this helps others at some point.

David, November 2023

Thanks for your reply, spot on. Looks like the problem is the wash pump start capacitor (4uF, 400VAC). I have an old 1uF 1000VDC capacitor which I connected in place of the original cap, in the hope that would give the motor enough energy to start. The motor now starts and the dishwasher runs though its cycle ok. So seems I had two problems at once: bad inlet valve and bad starter cap. Now I can buy the correct replacement cap with confidence it will not be wasted.
DW920 reputation comment based on this review site:
http://www.productreview.com.au/p/fisher-paykel-nautilus-dw920.html

Don, September 2012

You are correct about the way it senses that water is present and deep enough. Your fault is usualy caused by the wash pump not starting. After the drain period of about 20 secs you should hear water inlet start and the wash pump start. Can you hear the wash pump actualy start running or is it just humming and trying to start? I would replace the start capacitor first as that is a common failure. Very rare for the wash pump to fail on this model. Don't know where you got the poor reputation info from. I find this model & the 820 to be very reliable. Main problems were minor. Broken door springs, cracked or broken plastic on handle and start capacitor are the usual faults. Depending on where you live there are rebuilt PCB controllers available.

Lincoln Appliance NZ, September 2012