Sunday, August 12, 2018

Bosch SHP65T56UC dishwasher won't work, but drain pump constantly cycles

Problem:  For no visible reason, and suddenly, a Bosch dishwasher (such as a 500, 600 or 800 series, our model SHP65T56UC) starts with the following:

-  No indicator lights or display
-  Does not respond to buttons
-  No beeps or lights of any kind

and, most importantly:

-  The drain pump turns on continuously, or cycles on and off over and over / periodically, with or without the door open, even though the machine is not on and has no water in the tub.

This may happen right after plunging or otherwise clearing a clogged sink drain.

Power cycling at the breaker does not help.  Pouring water into the DW to try to fool it also does not help, though the pump will happily drain whatever your pour in.

Potential solution:  A small (possibly tiny) amount of water has leaked in to the bottom of the dishwasher, tripping the flood protection.

Basically, the bottom of the dishwasher is the last place to catch a leak.  So there is a small float, made of Styrofoam, built in to the bottom of the unit.  If water leaks from the wash tub into the bottom of the machine, it will shut off and run the drain in an effort to prevent flooding.

I know the description above does not really help very much.  I read similar descriptions on other sites but did not know what I was looking for.  So here is some pictorial help.

The first thing most DIYers may want to do is to remove the kick plate at the front of the machine.  Good, do that. 

But all you will see is an up/down leveling screw and an otherwise impenetrable wall.  You can't get in that way - you have to pull the unit out of the counter.  Bummer.

Fortunately, this is not (usually) too hard.  Installations vary, but many under-counter installs will use simple mounting brackets at the top, like this:

Unscrew any brackets (often 2), then pull out the dishwasher.  (It's actually fairly light, so there is little worry it will hurt your back or scratch your floor.)

On some installations, the top sound insulation (matting) will get caught up on the counter.  You can just ignore this, to an extent, and pull the DW out anyway (I did) or you can go to the bottom and crank the DW all the way down.  If you do this, be sure to level it again after pushing it back in to the counter.

Also, when pulling the DW out, keep in mind that the drain hose and/or electrical cables probably run into an adjoining cabinet.  Make sure there is some slack there so they don't end up getting pulled out of the DW machine itself.  When you shove it back in, be sure the pull the slack hose back through to the opposite cabinet so it doesn't get in the way of the DW itself.

After about  8-12 inches, you will be able to get to the left-hand corner of the DW.  There is no panel there - it is fully open, covered only by the soundproof matting.  Fold the matting up and out of the way:

My handy-dandy flashlight is making the otherworldly glow there.

Get down there and look inside, and you will see this:

You are staring at the white, plastic bottom floor of the DW.  

See that  round area in the middle?  That's the overflow "tray".  It's nothing more than a circular depression in the bottom of the DW. 

Look closely and you will see the the styrofoam "float" resting inside.  Stick your hand in there, you can feel it.  The plasticky box on top is the float switch.

So: if water leaks into the bottom of the DW, it collects under the styrofoam thingy, which rises.  The switch activates, shuts down the DW, and keeps the drain pump cycling until things dry out.

Chances are, when you stuck your hand in there, you felt a little bit of water with your fingertips. That's tripped the flood protection and shut down your DW.

Now, if you didn't feel any water, and don't see any, then one of two things has likely happened:

-  The float switch has gotten stuck in the "up" position; and/or
-  The float itself has gotten stuck in the "up" position.

In either case, you will need to replace the offending part(s), or otherwise figure out how to get them functioning properly. 

In my case, there was only a tiny amount of water around the float - just enough to trip the switch.  Cleaning it up with a couple of wads of paper towels was all that was needed to resurrect the DW back to working condition.

I was surprised by this, as I was expecting at least a half-inch of water filling up the DW bottom in order for the flood protection to trip.  But not so.

 In fact, there was so little water in there that I would have to say this was a premature trip.  There was less than a millimeter of water, and not even enough to fully surround the float - barely a Dixie cup full, if I had to guess.  To my mind this is not enough water to justify disabling the DW.

On the other hand, the bottom of the DW should be bone dry all the time.  So I can't really fault Bosch for being conservative here.  I wish they hadn't been, since it cost me time, but I can see their side of it.

I can also see why they felt unable to put some kind of error message on the unit display - they wanted to shut everything possible down to prevent electrical problems due to possible flooding.  But I'm still rightfully annoyed all to hell by that, and I'm the customer, dammit, so I'll be annoyed if I want to.

A lot of people report that this problem occurs when their sink becomes clogged and they end up plunging it to clear it.  I'm not sure exactly what happens that makes the DW leak water, but that is undoubtedly what occurred in our case.  

I've cleared the sink drain before, but this one was unusually difficult, and it required a lot more work than usual - and that is saying something, for our kitchen sink.  It's been a mess ever since we got the new DW, so perhaps the DW is dropping more junk into it than our old model did.

I also - wisely or not - use the "5-second plumber" pressurized gas canisters a lot, since clearing our sinks seems virtually impossible without them.  Somehow, a tiny bit of water leaked into the base of the machine during this last round, even though it wasn't an issue the previous three bouts.

Now, sure, my (excessive?) efforts to clear the sinks could have damaged something - there could be a crack in the internal DW drain hose, or something else I broke.  So if the DW shuts down again, I'll probably call a guy to find and fix the leak.  But there is no need to do so if all the repairman has to do is sop up a tiny bit of water due to a backed-up sink drain.


  1. I found this super helpful. VERY long story short this walkthrough was extremely useful for me to replace my float switch. Although on my Bosch dishwasher it was accessed through the front and not the sides. Thanks!!

  2. A detailed and precise explanation why my dishwasher stopped working after plungering the kitchen sink drain. Followed the directions and my dishwasher is back in business and no more hand washing. Thank you!