How to Troubleshoot & Replace Bosch AP5984938 / 12008381 Circulation Motor And Heater Assembly

New heat pump saved our lives! We bought a 500 series Bosch from someone dirt cheap and they thought their dishwasher was just crappy. Turns out heat pump burned up and needed replacing. Now this is officially the best appliance in our house. Cleans like a beast! Customer service was 10/10. Great people! 

Replaced circulation pump 

I ordered a Bosch circulation motor and heater assembly from AppliancePartsPros.com. It arrived sooner than expected and was an exact replacement. I watched the installation video and had it replaced without any problems. Installation was easy and fast. I highly recommend AppliancePartsPros.com. The dishwasher works like brand new. 

Replaced pump/heater with OEM part from AppliancePartsPros.com Watched the video from that site before attempting the repair. After watching the video, the repair was easy. The most time-consuming was disconnecting water, drain, and electrical in order to pull out the machine. Reconnecting these lines also required a lot of patience due to the way my machine was originally installed. 

Our local appliance repair man was disappointed to find that my dishwasher didn't have the heating element inside the machine. So he gave up and did not fix it for us. My husband (an exterminator) did some online research, ordered the part, pulled the machine out from the counter space, replaced the water heating part, and it works great. I am also very impressed that the part arrived in 2 days. This error code can mean that running your dishwasher is potentially dangerous, if water is leaking into the heater. It can also mean that hard water deposit is keeping the heater from working. Note that this error code can also mean that your drain is plugged up. Check that first before ordering parts! Also check the drain screen, and scrub it well. 

E20 is a motor resistance error. This was my first ever dishwasher repair. I went pretty slowly. Assuming the problem was motor failure, I bought a motor and accessories. While taking apart the machine and removing the current motor, I flushed all the residual water from the motor and shook it quite a bit. While I never saw any particular “thing” that may have been jamming the impeller, I temporarily reconnected the power to the unit and start a rinse cycle. To my surprise, the motor started right up and no E20. I opted not to even install the new motor. Note, reinstalling the motor was easy, but the original hose clamp was very cheap and was virtually impossible to reuse. So I opted to use the $14 replacement hose clamp that was very high quality. We have now run 5-6 loads and no issues whatsoever. 

After disconnecting water and power, I pulled my Bosch dishwasher out. On the bottom right of the machine, I disconnected the control board housing and set it aside to reach the pump. After opening the pipe clamp with a screwdriver, and removing the black rubber retainer, I could pull the pump loose and unhook the three wire harnesses. Before installing the replacement I wanted to be sure the heat pump was bad -- other reports indicated it might be a control board issue. Another commenter here provided the exact instructions for testing with my multimeter which was a huge help and allowed me to confirm that the pump was bad. Installing the pump was a little awkward, but straightforward. I wiggled it in place, first positioning the pipe clamp where I could reach and tighten it. I also put a bit of dish soap on the rubber intake port to help it slide on easier. This was not too hard to do, but I think I could have laid the washer on its back, which would have made it easier to reach everything. 

I used a multi-meter, to test the pump while it was still installed and discovered that the heater inside the pump had failed. It was not technically difficult to do the repair and someone who is somewhat handy should be fine. 

This was a fairly straight forward repair. I'm fairly handy but never attempted something like this before. There were a couple of good videos on YouTube on how to replace this part so I felt very confident I could do it myself. My 14 year old son and I did this in about one and a half hours. Only hiccup we ran into was not taking the plug out of the back of the dishwasher first. We cut the power but left the cord attached in the back of the dishwasher. Make sure to unplug and take that off. It will make taking the electrical box out much easier. 

I followed a Youtube tutorial on how to replace this part for a machine that was a match for mine. It was simple and from flipping the breaker to OFF and back to ON this job took me less than 1 hour, and that includes pulling out the dishwasher from under the counter and replacing it.