Bosch SHU5305 Intermittently Shuts Off

[Bosched]

Hi, from the posts I've read so far it looks like I found the right place to hopefully get some questions answered about my broken Bosch SHU5305 Dishwasher.

The problem: For the last couple of weeks about once or twice a week the DW would suddenly shut off (led indicator lights and countdown timer display - black) about halfway through a wash cycle. Opening the door, and cycling the power on/off switch would restore power and the wash cycle would continue from where it left off. A couple of days ago the intermittent problem surfaced but cycling power did not correct the problem.

I thought the door switch might be faulty but when I removed the lower front kick panel I noticed the capacitor on the circulation pump was hot and leaking oil. I've since replaced the capacitor but the problem of the DW running and shutting off is still there. In fact the DW will run for about 3 minutes and then shut down. I tried to run the diagnostic test but during the test I loose the display lights.

I don't believe the problem to be input power related because even with the indicator lights off if I push up on the red float rod the evacuation pump motor starts and the water is pumped out of the DW.

I carefully inspected the control board and there are no signs of open solder joints.

Questions:

1. Is there an overcurrent sensor on the circulation motor that could be sensing an overcurrent condition and therefore removing power?

2. Is there an temp sensor on the circulation motor that could be sensing an overtemp condition and therefore removing power?

3. Could a fault in the heating assembly be causing this failure?

4. Are there any fault conditions that would cause the control board to shutdown (lights off) the DW?

5. Are there any schematics/wiring diagrams available for this DW? So far I have just removed the door panel but I have not found any diagrams glued on it or any of the parts of the DW I can see.

Currently I'm leaning toward replacing the circulation pump motor. My logic being that if the motor drew enough current to overheat the run capacitor then maybe there is a short in the motor. I just hate to spend the money on a new motor only to find I really needed a control board.

My next step will be to remove the DW, remove the circulation motor and then perform a bench check on the motor.

Any additional advice would be greatefully appreciated.

Thanks,
Rich B.

[Bosched]

Update...The dishwasher is working for now. I found the wiring diagrams and additional troubleshooting info at AppliancePartsPros.com under the SHU5305/06 (http://click.linksynergy.com/fs-bin/click?id=YO6223WzStY&offerid=122738.532950401&type=10&subid=) model number. What a difference it is to not have to troubleshoot blindly.

Anyway, I'll try to answer my own questions. Someone please correct me if I'm wrong. Here goes:

Q1: No
Q2: No
Q3: No
Q4: Yes, I'll explain in my solution below
Q5: Yes, See AppliancePartsPros.com (http://click.linksynergy.com/fs-bin/click?id=YO6223WzStY&offerid=122738.458203423&type=10&subid=)

Troubleshooting steps: I checked resistance of the circulation motor and it read 10 ohms. My biggest worry was what was making the control panel loose power. I knew the DW had power because I could manually turn on the drain motor (I called it evacuation pump earlier) by lifting up on the red float rod. By manually probing the control module and looking at Bosch diagram #36 I realized that pin 12.4-8 supplied line power to float switch e6-1. When the float switch was enabled power was transferred to e6-4 which is connected to the drain motor m3. At this point it seemed my power loss problem was probably related to the control module itself. I performed another careful inspection of the control module solder joints and discovered that the solder joints around the transformer looked like they had gotten hot. With nothing to loose I resoldered the transformer connections and so far everything is working.

Solution: My loss of power problem was due to a faulty control module (poor solder joints).


Rich B.