Hi, my wife went to start our Dishwasher (Bosch SMU7056UC/14) yesterday and it did not run/start properly. The unit just was “humming” (electrical sound like the timer is trying to do something). Normally we hear the pump run first followed by water entering the dishwasher but all we hear is the electrical “hummm”. When I reset the dishwasher (hold Rinse&Hold and Quick Wash buttons down at the same time) it seems to me that it is taking much longer than it used to. We haven’t had to reset the cycle for years but I seem to recall that it may have taken 20-30 seconds to reset, but it now takes just over 3-minutes. Again I’m not sure if 3-minutes is normal but just wanted to provide you with that information.
I replaced the water valve in 2005 and before it died you could tell what part was going bad because of the excessive noise.

Any advice or things to test to help me figure out what is wrong will be greatly appreciated.
Thanks.
Jeff

Hi Gene,

Thanks for your reply. The serial # is: FD730200037. I did look at tech diagrams I found on the appliancepartspros website (wiring, timing, circuit) and confirmed that the drain pump should run first for about 25 seconds after turning on the unit (this is what we normally hear before water starts entering the unit). But this pump is not running. I did check the voltage at the drain pump after turning the unit on and each of the three terminals (gray, brown, black/white) to ground were showing 115V so power appears to be going to the drain pump but it is not running. No noise at all. The only sound we hear is an electrical clicking/humming which I believe is the timer running. I haven't tried to locate the circulation pump terminals but I don't think they get turned on until the drain pump finishes its initial cycle. I did check the water valve voltage and it shows 0v across its terminal. So if the drain pump has failed, would that mess up the timer and prevent the other "timing" events from firing (i.e. water valve lets water in, circulation pump starts up, etc.).

Thanks again for your help :-)


/jeff

Hi Gene,

I pulled the wires off of the leads to the drain pump and the brown and white/green and black wires which are the "low side" wires are not connected to ground (i.e. infinite resistance). The brown wire goes to the water solenoid which goes to the float switch and then I'm guessing to ground (I have not confirmed that is the case via continuity testing). I have pulled the drain pump out and tested it by attaching to test cord and plugging into an outlet and it does run. I tested the float switch and it is working. The water solenoid appears to be okay (has some resistance but does have continuity). The black "low side" wire from drain pump goes to a capacitor (don't know how to test it) and the white/green "low side" wire from drain pump goes to High Limit switches (which I'm not sure how to test either). Since neither of these "low side" wires connect to ground (continuity test shows infinite resistance) the "drain pump circuit is not being completed. So could the problem be in the timer switch in that a "return" contact has gone bad and not performing the necessary connection to ground? I removed the black and white/green leads from drain pump motor hoping to see that it would run (that would indicate that the capacitor and/or high limit switches are the problem) but it didn't. I then connected them back to the drain pump and removed the brown lead to see if it would run (that would indicate a problem with the water solenoid and/or float switch) but it didn't. So I believe all of these parts are probably okay and another common path to ground is being prevented by some other failure.

thanks again for your help.


/jeff

Hi Gene,

Well, I took a much closer look at the wire harness that goes from the control panel down the door and into the unit, and as suggested by another blog I found when researching my issue, a wire within the harness had broken from the wear and tear of bending back and forth. The broken wire apparently got to a point where it caused enough sparking to burn/push through the plastic protective wrap. It wasn't easy to see when looking at the wire harness a couple of days ago but after removing another bracket to gain better access to the harness it was obvious there was a problem. I carefully cut the protective covering open enough to look at the bad area and sure enough the green/white wire was 99% broken. I was able cut it completely, strip both ends, and wire nut them together. I got the wires taped up, put everything back together, and my 17-yr old Bosch dishwasher is purring like a kitten once again!!

Thanks again for your help and patience.


Sincerely,


Jeff