Dishwasher Problem Diagnosis

[1990C4S]

I have an ongoing problem with my Bosch dishwasher not draining at the end of the cycle. The pump also runs 'randomly' for ten to fifteen seconds at a time on occasion. The wash cycle works as well as ever. It's a very good dishwasher...

Things I have eliminated:

- it's not the pump, I have cleaned the drain area and run the pump manually, the pump works properly and can pump all the water out

- it's not the drain line loop, the loop was missing, but I secured the drain line to the bottom of the counter and the problem persists, the dishwasher is not siphoning water or being back-fed from the sink.

- it's not a bad fill valve, the water never goes above the normal fill volume

I can lift the float switch mechanism by hand (the red piece in the image below) and force the pump to run, so it could be that switch mechanism, or it could be the control board.

Side note, I do have a slight clogged drain issue in the kitchen, but I need to completely replace the plumbing to fix it as the 'plumber' installed the kitchen trap in the basement ceiling and it's inaccessible. I don't see how the drain issue can be related, but they did occur around the same time. I would expect the a clogged drain would cause the dishwasher water to end up in the sink, and this has never happened.

The float switch is reasonably easy to swap and about $100. I have googled this with no luck, failed pumps are common, this issue is not common.

Any better ideas than playing parts swap-o-matic now? Maybe examine the (overly complicated) float switch before I buy one?

[cabmandone]

Can you pull the drain line from the washer and run it directly into the sink or elsewhere to make sure the stoppage you mention isn't having an effect?

[1990C4S]

Originally Posted by cabmando

Can you pull the drain line from the washer and run it directly into the sink or elsewhere to make sure the stoppage you mention isn't having an effect?

I can try that, but I was thinking of living with the issue until I fix the plumbing.

[billybek]

One of my neighbours had a house fire that started from the main control board of their Bosch dishwasher. There was a run of these that were problematic so make sure that yours isn't one of them.
If the pump is pushing against too much head on the discharge side (restricted drain) that may be problematic and the test listed above would be a good way to eliminate that possibility.

[cabmandone]

If you're thinking it's just a plugged trap, couldn't you go rent an eel and fix that problem?

[1990C4S]

Originally Posted by cabmando

If you're thinking it's just a plugged trap, couldn't you go rent an eel and fix that problem?

The idiot plumber built a trap from elbows, no clean out, and I can't get a snake in. And no vent, no AAV.

I need to replace everything he did. I have a very slight blockage, only evident when you drain a full sink. With the tap running it never backs up.

I will pull the drain this weekend and run a full cycle.

[cstreit]

Can you hook up a telltale somehow so they next time it is failing to drain you can see if the float switch isn't closing (switch issue) or is closed but the pump not triggered (board issue).

Maybe just two wires running from the switch and a continuity tester...

[cabmandone]

Originally Posted by 1990C4S

The idiot plumber built a trap from elbows, no clean out, and I can't get a snake in. And no vent, no AAV.

I need to replace everything he did. I have a very slight blockage, only evident when you drain a full sink. With the tap running it never backs up.

I will pull the drain this weekend and run a full cycle.

Put in a "Putnam county" vent (That's what we call them around here) That'll help with the slow drain when the sink is full. If you want to see if it will help, when you're draining the sink, swirl a spoon in the water until you make a vortex. Once the vortex forms the sink will start to drain faster. If this helps. Put in the Putnam County vent.
https://www.ebay.com/itm/255047334354?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=255047334354&targetid=1262779894769&device=c&mktype=pla&googleloc=9015981&poi=&campaignid=13917593257&mkgroupid=128459893881&rlsatarget=pla-1262779894769&abcId=9300613&merchantid=113478747&gclid=Cj0KCQjwqp-LBhDQARIsAO0a6aJRqOH0rVVAWMJOFdeMQW-DdEo_ENium9ls7nFKivp1vsB0V9z8Nu4aAngAEALw_wcB

[1990C4S]

Originally Posted by cstreit

Can you hook up a telltale somehow so they next time it is failing to drain you can see if the float switch isn't closing (switch issue) or is closed but the pump not triggered (board issue).

Maybe just two wires running from the switch and a continuity tester...

I'm going to empty the dishwasher completely, and check the state of the float switch, then fill it up manually and see if the switch closes...

[asphaltgambler]

Go to repairclinic.com, punch in your make / model - they have FAQ / issues that point to cause / most likely cause and part needed along with how-to pix and videos. It's all I use with any appliance, I highly recommend.

[masraum]

Originally Posted by asphaltgambler

Go to repairclinic.com, punch in your make / model - they have FAQ / issues that point to cause / most likely cause and part needed along with how-to pix and videos. It's all I use with any appliance, I highly recommend.

I've used that site and another very similar site several times over the years. They always pointed me to the correct solution, and then I've been able to purchase the needed parts at a great price.

[1990C4S]

Unfortunately my issue is not covered by repairclinic.com, but I did see there is a check valve that can fail. I find it hard to believe that backflow could fill the dishwasher.

I will check tonight.

[fintstone]

Did you look inside the dishwasher when the drain pump is running to see if there actually water in the bottom of the dishwasher (so that the pump running is necessary)?

I have had this problem and after taking the machine completely apart without finding anything that did not seem to be working optimally, I was able to cycle power a couple times to get the electronics working properly (circuit breaker). Lots of electronics in some of the newest models...almost like my laptop (or my wife)...needs a good rebooting now and then.

[billybek]

Oh, forgot about this. My Kitchenaid dishwasher had two pumps. One pumpout/drain pump and a wash pump.
The impeller fell off the wash pump after only about 2 or 3 years.

[1990C4S]

Originally Posted by fintstone

Did you look inside the dishwasher when the drain pump is running to see if there actually water in the bottom of the dishwasher (so that the pump running is necessary)?

There is water, it needs to run. It actually needs to run longer.

[1990C4S]

Originally Posted by billybek

Oh, forgot about this. My Kitchenaid dishwasher had two pumps. One pumpout/drain pump and a wash pump.
The impeller fell off the wash pump after only about 2 or 3 years.

One pump on my Bosch.

[stealthn]

Fixed mine several times, almost always blocked drain, even found glass blocking it once. I would do what others have said, hookup another line from the drain right to the sink and run it

[fintstone]

Originally Posted by 1990C4S

There is water, it needs to run. It actually needs to run longer.

That was the case with mine as well.

[cstreit]

Originally Posted by masraum

I've used that site and another very similar site several times over the years. They always pointed me to the correct solution, and then I've been able to purchase the needed parts at a great price.

Same here. They have a video for every darned common problem my appliances have experienced... ...and the parts to fix it. Big fan.

[1990C4S]

SO last night it pumped down perfectly.

But two hours later it was full again.

I need to fix the drain connection and clean the check-valve next.