KM/WP DW losing water during wash after sensing

[peterh770]

The bf has this great KM/WP dishwasher that has developed this issue recently:
Start dishwasher, usually the sensing or the normal cycle
Fills and starts to prewash
Sense pause
Prewash continues. After a few minutes, you hear the recirc pump starting to suck air.
Sense pause
More washing, more and more air sucking.
Drain
Fill and starts main wash
All good
Sense pause
More washing, but after about 5 minutes, starts sucking air again.
Sensing pause
More washing with more and more air sucking.
Here is where I start to get concerned, because "hi temp" is selected, and if the water level is getting lower and lower, could it overheat, melt things, become a fire hazard?
Sensing. How can it sense with so little water in there?
By the end of the main wash, it is dry.
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It doesn't have this problem with the rinsing. My guess is because there is no sensing pause during them. The first rinse is short, but I would not call it a purge. The last rinse is VERY long, even without the "sani rinse" selected.
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Is something happening with the flapper valve when the machine pauses to sense? Is the drain pump running the entire cycle, or is water slowly siphoning out? The drain hose does a high loop to the top of the cabinet before hitting the wall drain.
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When it first started this, I took the wash arm assembly apart and cleaned out a couple of screws, broken glass and twist ties from the sump. I cleaned the screen and got rid of calcium deposits. The flapper valve was intact. It seemed to help the problem, but it is still happening. I could find no YouTube video for this problem.
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Pics to follow (with model sticker).

 

[peterh770]

Sure enough. I just went over to check it during main wash, almost empty of water and the heating element was glowing bright orange. Dumped about 1/2 gallon into it, restarted, sounds OK for now...

 

[peterh770]

[No message]

 

[henene4]

First instinct would be to make sure where the water goes. Disconnect drain hose, hang into a bucket. Should show when water is comming out, and how much, or if even.

Next would be to check if it fills properly. Maybe it just about fills enough to recirculate, and thus the water level slowly drops as it heats or as dirt absorbs water.

Maybe it's kind of a slow leak. Dunno who it was but somebody on here had a drainhose on a DW crack ever so slightly, which dripped beneath the machine without them noticing, causing a huge water damage.

 

[peterh770]

I dumped in the extra water at about 1:03. It started sucking air a few minutes ago and just did a sense pause. Now it is definitely sucking air. I hope the heating element has cut off...
About 15 minutes for it to start...

 

[appnut]

Peter, my bf has a similar WP TT.  His does similar.  I've been twice to his house.  The first time I noticed the DW cavitating, but didn't pay a whole lot of attention because I was trying not to get all in his face with his appliances.  Plus, I couldn't stand to be near the kitchen when it was getting to that point--to me it's the equivalent of a puppy being hurt or baby crying.  (He rinses everything off so he has no clue the machine isn't properly performing).  The 2nd time I visited I was there for a number of weeks and I was able to be more assertive--let's just say he welcomed me doing laundry, some cooking, and willing to load the dishwasher.  When he was at work and I would run the dw, I'd add more water, especially during main wash.  His model has no sensors so it doesn't pause to "read" water--but main wash is only about 18 minutes long.  It would still "lose" water after I'd added more during the main wash and the last rinse.  I did observe somewhat of a pattern.  But it seemed to not have such a pronounced water loss when the machine wasn't loaded very much.  I think I even PMed JohnL while I was there and described the scenario so  similar to what you observe, but John couldn't come up with what was causing it.  Ted's model is a WP DU1050 (pretty pathetic one can walk into a kitchen for the first time and can Identify by model # what the dishwasher is). 

 

[revvinkevin]

 

 

Peter, during the fill, do you know if it "times out" (and the motor starts) before the water level is reached, OR the water level float shuts off the inlet valve and then the motor starts?  

 

This may have little to do with anything, but I was thinking IF the float stops the inlet valve first, perhaps you can modify the shaft on the float by shortening it slightly, to get slightly more water in the tank before it starts.

 

It's just a thought....

 

Kevin

 

[ken]

I know Im talking about a different animal but a couple years ago our 1996 GE was losing water during the wash and rise cycles. Didn't make sense to me but I found the flapper in the pump housing that controls water recirculation/wash or drain was made with a hole in the center of it. It originally had a rubber plug in the hole which had deteriorated over time and fallen out. As a result the machine was constantly losing water through the hole when in recirculate mode. After doing some needed parts replacement which included a new pump, which of course had the plug in the flapper, the problem was no more.

 

[peterh770]

Hey Kevin,

No the machine fills up propery for each cycle segment. Granted, it isn't a whole helluva lot in this TT, but it is right up there. It does do a "purge" fill where it starts, stops and throws water for about 5 seconds, then finishes filling. My guess is that it cleans the sensor.

Hey Ken,

My first thought it was the flapper, but it was all intact. Then I thought siphoning, but hose makes a high loop. Unless there is something in the wall for the drain, I may not be able to figure this out without a $$$ plumber call. And then why only on the prewash and main wash, but not the rinses...

 

[ken]

That it happens only on the washes and not the rinse is the strange thing. As you already stated it doesn't do the sensing pause during rinse. That might give a clue to the problem. Just what is the machine sensing during that function?

 

[johnb300m]

Two things.

1. Is this machine maybe doing Automatic Purge sequences to flush the filter in prewash and main wash portions? But not "backfilling" the water that was pumped out?
The Tech books in these I remember, stated they do a 5sec. drain purge and a 10sec. re-fill. Is it skipping the re-fill?

2. Why is your heater element glowing red???? IME, I've never seen a DW heater get red hot. That says there's an issue to me. DW elements are often kept under 1000 watts. It should not look like an oven element. It's my understanding that that would be highly dangerous.
Maybe one of the actual appliance techs in here can weigh in.

 

[henene4]

As I said, do you know where and how the machine is loosing it's water? It could verry well be not refilling enough after the purges.

Given this happens during the pauses, thus without recirculation, could there be any seal just below the water line when it is not recirculating that might have gone bad? Idea being that as long as it recirculates, the water level is below the source of the leak, and as soon as it dosen't recirculate, the water pools and thus leaks?
Thinking of something like the seal between the sump module and the tank.

The glowing red is due to no cooling of the element by water as there is no recirculation happeing.

 

[peterh770]

John300m:

1) No, the machine fills about 30 seconds, throws water for about 5, then finishes filling all the way. There is no purge drain during the fill.

2) The element is glowing orange because there is not enough water in the machine. The doctrine states that it will automatically heat the water to 120 or 140, depending on the cycle choice. If you select "Hi-Temp" the water heats to 150. I like to use the hi-temp option, but regardless, the machine will heat to the correct minimum temp.

Henene4:

No, the machine fills to the required level with every fill. Only on the pre-wash and main wash does it start to lose water after about 15 minutes. The filling is not the problem. Now, if the machine is supposed to detect not enough water, then it would be another story, but I never heard of a dishwasher doing this.

I think you are heading in the right direction, though. I'm thinking that when recirculation stops, the water level rises in the drain hose, enough to trigger a slow siphon. I also have a feeling there is no drain vent where the dw connects to the house drain. Without the vent, there could be suction in the line.

 

[johnb300m]

Aha. That's a key thing.
There must be an air break in the drain line. Or all sorts of weird things can happen.

 

[magic_clean]

Pete

there is a factory installed drain hose loop that is connected to the drain pump outlet. From there the hose loops up the left side of the tub and is clipped into a retainer. It is vital that the hose is securely mounted in the retainer. The 6' drain hose is connected to this loop just behind the toe kick.

Then the 6 ft drain hose must be supported under the sink to be at least 20" above the floor or better yet; looped just beneath the counter top and then ported into the disposer or sink tailpipe drain connection.

The initial 'purge' fill that you mention, actually serves to condition the interior of the machine. This is important in installations with very hot incoming water.

HTH......L.P.

 

[murando531]

Have you tried removing the wash arm and filter assembly and checking the inlet grate? If not, it wouldn't hurt. Not only can you make sure it's clean and free of debris and large objects like bread ties and tooth picks, but there is also a small rubber flapper valve, almost shaped like an army medal (rectangular top part with a circular piece hanging down) inserted into a slot that divides the drain chamber from the grinding chamber. This prevents water from being forced into the drain chamber during the wash portions because of the pressure produced by the main pump. It should only open when the drain pump kicks on and puts negative pressure on the chamber. If there is anything at all causing it not to seat properly, debris or scale buildup or otherwise, there can be just enough water forced through to push water up the drain hose.

There is also a check valve in the drain hose, where the elbow fitting attaches to the outlet port of the dishwasher. This can definitely cause a siphon, even if the hose is looped on the side of the machine properly, if there is anything blocking it from sealing completely. This happened with my Maytag MDB4709, which is the same Voyager platform as the machine here. After back flushing the hose and cleaning it out, I never had another problem.