FIXED SHX46A05UC/21 Bosch dishwasher stopped mid cycle

DoraBosch

Premium Member
Joined
Nov 30, 2018
Messages
4
Location
WA
Model Number
SHX46A05UC
Brand
Bosch
Age
More than 10 years
The dishwasher was running and it just stopped on its own somewhere in the middle of the cycle. There were no LEDs lit any more. Pressing the On/Off switch does nothing. I get no LEDs to light up at all. I have verified with a Fluke multimeter that there is 120VAC going into the dishwasher at the wirenut connections at the bottom right. With the breaker off, have verified that both maintained contacts and the momentary contact on the on/off switch are working correctly. With breaker on and on/off switch on, I measure 80VAC going into what I am guessing is the power connector on the controller. Not sure if this is the correct voltage as I would guessed it would have been 120VAC but the red wire is coming somewhere from the bottom so perhaps there is a step down transformer?
-Does this look like the controller has failed and needs to be replaced?
-Is the 80VAC to it correct?
-What typically fails on these controllers?
-Is there any documentation available on what the connections to the controller are so I can troubleshoot it further?

Thanks for any help.
 

DoraBosch

Premium Member
Joined
Nov 30, 2018
Messages
4
Location
WA
Low voltage to control module due to flow switch being open in Bosch dishwasher

So I did some more troubleshooting. I found the wiring diagram tucked away inside and that was very helpful but sadly I am still stuck. The control module had a bad solder joint. I desoldered the relevant relay (K1) and tested it by applying coil voltage of 6VDC and the NO and NC contacts on it work fine. So I resoldered the relay back in. I had good line voltage. So then I started chasing why I only had 80VAC going into the control module. The neutral goes to the flow switch (e5) then to the heater element (r1) and then to the high limit thermostat 185degF (f5) and then finally to the control module. I suspected it may be the high limit thermostat so followed a Youtube video from Repairclinic to take it all apart. Turns out the thermostat was fine as I had continuity across its two red wires. The heater element was fine too as I had measured 12 ohms across it. The issue was the flow switch was open. I was able to manually actuate the flow switch with a screw driver without actually removing it.

So the question is how are you supposed to get flow to actuate the flow switch without the controller getting proper 120VAC power? It is a bit of chicken and egg question in my limited understanding and so would really appreciate some input with this? Has the controller failed entirely? If I put a new controller in, the way things are currently, it will still only get 80VAC so how will it work? I have even tried applying 120VAC directly to my old control module using just the 2 wires to see if I could get any of the mode LED buttons to light up but was unable to.

Please help!!!
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
100,796
Location
McMullen Valley, Arizona
Hi Dora,

You might want to message jeff1 and refer him to your thread here, he's very good with Bosch Dishwashers. I haven't worked on or had training on any Bosch products or I would help you.

Jake
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
23,725
Location
Ontario, Canada
Hi,

When ever I see low or odd voltage it is usually an open/loose/burnt neutral.
I'd concentrate on that side to see where the 120 volts is being lost.

jeff.
 

DoraBosch

Premium Member
Joined
Nov 30, 2018
Messages
4
Location
WA
Thanks Jeff. You were right. The low or odd voltage was indeed due to the neutral. The neutral connection goes through the heater element, high limit thermostat and flow switch. I suspected the high limit thermostat based on online research and so had to disassemble everything to get to it to test. Turns out the high limit thermostat and heater element checked out fine.

It was the flow switch that was open since there was no flow and hence the AC low voltage. So then that pointed to the controller board as having an issue since the LEDs would not turn on. Ended up replacing the controller board and it all worked fine. Wish I had known about the low voltage being due to there being no flow as taking that all apart and putting it together was a chore.

Replacing the controller board other than the cost of the controller board was easy. I was quite impressed by how well these dishwashers are built in that one can take it all apart and put it back together and it all works fine without any leaks or issues. The poor solder joints in the relays for the controller board were about the only weak part that I have found so far.
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
23,725
Location
Ontario, Canada
Thankx for the update :)

jeff.
 
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