Whirlpool Dishwasher ADP5540 flashing

23 Aug 2008
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New South Wales
United Kingdom
Help! Our Whirlpool ADP5540 is not washing properly (incomplete cycles). The power switch light flashes 4 times. What is going on? Heeelp!
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F4 = Draining Failure. If it's draining ok then the pressure switch is stuck, full of gunk or faulty.
Jackpot. You're a genius, but you knew that already lol.

Sure enough, took the bottom hatch off and located the pressure switch assembly on the side of the sump. It twists off once you release a retaining tab. Not all that easy to get free, but when I did I found it to be full of gunk. Gingerly snapped off the tabs holding the strainer head and cleaned out all the gunk around the diaphragm which actuates the microswitch. Presto.

Now let us know one thing: how does one stop the buildup of gooey gunk that seems to collect around the insides? We're using a good brand of dishwasher detergent. it's as if you need to rinse it every month with hydrochloric acid just to clean it out (just kidding about acid, but it does need something a bit drastic).
Never put foodstuff in a dishwasher. I rinse our stuff before it goes in. Never had a problem with last 2 Whirlpool dishwashers.
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"Sure enough, took the bottom hatch off and located the pressure switch assembly on the side of the sump. It twists off once you release a retaining tab."

Can you tell me what you mean by 'bottom hatch'? I'm guessing you can't access the pressure switch through the sump with the filter removed. I can see the pressure switch membrane (black grid) but I can't see how to remove it, hence I think I'm in the wrong place.
Copied from a private message reply by Cartesia, who hopefully won't mind me posting it here to provide advice to everyone else:

Thanks for your question. Sorry i've taken a few days to reply.

There is no point trying to access the switch from the inside of the dishwasher....you have to get at it from underneath it. Lay the machine on its side (RHS as you look at the control panel from the front) and take off the bottom hatch. Careful the edges are sharp.

The switch is a bit hard to access...the retaining tab is near the back. The order in which you remove the pressure switch is (from memory):

1. I think the switch body will turn (twist) off the sump body a fraction of a turn before it hits the retaining tab
2. The retaining tab is at the back where it's hard to access...it just flexes a bit to release the switch body
3. Once the switch body is released from the sump (say a quarter turn, no more) you have to flex the hoses by hand to ease out the switch assembly. this takes a bit of juggling and flexing. I didn't remove any retaining clips.

When you get the switch off you have to carefully prise loose the cap/head piece that protrudes into the sump. Be careful not to snap the retaining tabs. You will then be able to access the switch diaphragm (be careful it is in 2 pieces). You can clean out the gunk, wash and carefully reassemble it.

This is from memory - hope it's ok.

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