Question about Bosch SHU3306UC Built-in Dishwasher

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Bottom tray with float gets full of water and won't let water in until I soak it up with a towel. then it will allow water in and continue. Took float out and cleaned still have the problem. What causes the bottom tray to fill with water? Thank You!

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  • jbcmjones_11 Dec 09, 2009

    Thanks for your reply,
    You mentioned aqua stop, not sure what that is. I understand how the float works, I guess I really need to know why I'm getting so much water in the white plastic tray that it activated the float switch?

  • jbcmjones_11 Dec 10, 2009

    Thank You. Your advice is dead on. After watching it run for a cycle or two I noticed a leak toward the water inlet system as it was filling. I will Pull it out today to see if it's just a fitting or a component leaking. I'm not sure how deep to get into it it is at least 6 years old. If I have further questions I will certainly ask your advice.

  • jbcmjones_11 Dec 11, 2009

    Thanks to everyone who helped. Following the troubleshooting advice I found the Problem. There was a small leak between the water supply assembly and the water level switch housing. Took them apart, cleaned them then just put a small bead of sealant on them when I put them back in. No More Leak works great again. The machine was simply doing what it was designed to do, buy not letting more water in because of the leak.



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Hello JbcmJones, It would appear that the discharge pump isn't allowing the water to properly drain. Sometimes it happens when a glass breaks and parts of the broken glass get down into the sump area and obstruct the drain area. In order to determine what the issue is, let's go through some steps to get at the problem.

First, remove the bottom rack and the spray arm. Now look for the the sump screen and remove it, as any blockage could have gotten past it and into the lower pump assembly. You can soak up any excess water to make this easier or use a wet/dry vac to do it too, which sometimes makes it easier to get out most of those obstructions.

Now very carefully check for any items (broken glass, plastic caps, pieces, etc.) that may have gotten into the sump and could be causing the dishwasher not to properly pump out during the drain cycle.

Once, you've done that, also check your "air-gap" (back flow device), if so equipped and installed on your drain line. These are typically installed at the sink top and are round metal caps with a filter screen inside them. If you have one of these, remove the cap by pulling and twisting it up and off. Remove the screen filter and clean it out and replace it.

Lastly, check the discharge (drain) line where it connects to your sink drain, either above the P-trap, or at the disposal, if you have one. You'll have to remove the hose clamp and check for any possible obstruction in there. While you've got it off, you can blow into the line to see if you've got a clear line all the way back to the dishwasher. If you hear air, then the line is clear. That should take care of the drain line issues.

One last remotely possible issue, might be that the microswitch is defective. It might be working intermittently and needs to be replaced, but not so sure that is the problem. Based on your observations and comments on the dishwasher working, once you have the excess water removed, I don't think that's the problem.

You should be able to hear the switch click when you lift and lower the float. Other than that, you would have to have a multimeter to verify it's working, but again, I don't really think that's the problem, since you get water flowing into unit after getting rid of the standing water.

Here's a line drawing that you might find helpful as you look at the sump area inside the dishwasher.

Hope you find this Very Helpful and best regards!

Posted on Dec 10, 2009

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Hi, Having seen many, many of the issue you are dealing with I can direct you to check several possible causes. 1) Improper install with no "hi-loop" in the drain line. This allow's water to flow back into the machine when not present or previously there but the "hi-loop" has fallen down. 2) Drain line connected to a garberator/food disposer without any form of check valve or loop as I mentioned in point # 1. 3) Faulty inlet water valve. Bosch D/W's have a history of defective water valves which can potentially allow water to enter the unit even when not energized. 4) The outlet pump is faulty and not draining the machine sufficiently and therefore creating a overfill scenario somewhere during a normal wash cycle. 5) The drain hose could be kinked or obstructed somewhere between the pump and your household plumbing. 6) A leak has developed with one of the component's under the tub, i.e. circulation motor & pump face seal being the most common. These are actual problem's I've serviced on many occasion's. It can be any one or a combination of several, though not likely. Hope that provides you with the help you came to fixya to find. Let me know if I can assist you further. Good luck. macmarkus :)

Posted on Dec 10, 2009

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Here is the troubleshooting that needs to be done. Beneath the main chamber of the dishwasher, by three inches or more, is a white plastic tray. It sits almost at the floor, and it may not be obvious that it's a tray capable of holding water. The overflow water spilled into that tray, which in turn caused a float in the far left side of the tray to lift and shut off the water intake valve. So long as that valve is closed, your machine wills not run. You might want to purchase a aqua stop.
Thanks for contacting

Posted on Dec 09, 2009

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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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I have a Bosch SHV. My sink drain backed up, and the water accumulating in the sink then migrated to the dishwasher, through the drain pipe, causing the dishwasher to fill up and, it turned out, overflow a little. When I turned on the dishwasher, the water drained, but no new, clean water came through the hot water pipe. The drain just kept running, but nothing else happened.

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