Bosch Dishwasher SMV40C10GB/46 not starting and Tap light flashes

[Twoten]

When the above machine is started and door closed the Tap light flashes continually within about 1 second.
The pumps do not run, the inlet valve does not operate. No sound of relays operating on the PCB.
There is no water in the base and I have checked the operation of the float switch contacts.
The pumps turn freely by hand.
There’s continuity through the inlet valve.
The element test OK.
There are no signs of damage to the PCB.
I am running out of ideas on this.
Any help would be appreciated.

[boselecta]

Could be the reed switch 611317 has failed, worth trying?

[electrofix]

if check water light comes on it a water fill problem

if it flashes it a technical fault

Dave

[Twoten]

boselecta wrote:Could be the reed switch 611317 has failed, worth trying?

Thanks for the suggestion.
The contacts of the reed switch were closed-circuit. When I moved a magnet across the impellor. it moved and the reading pulsed.
Also, the machine didn’t start to take any water so I wouldn’t have expected the reed switch to operate.

[Twoten]

electrofix wrote:if check water light comes on it a water fill problem
if it flashes it a technical fault
Dave

Thanks Dave,
The light flashes continually, not for a number of pulses.
There were no other lights, should there be a way of narrowing this down to a fault code?

[electrofix]

bosch tech is few and far between

go through the dishwasher manuals on manualslib there are a few tech manuals mixed in. may not be exactly the same model number but some of the tech is tranferrable you just have to see if there is a similar built machine

Dave

[Twoten]

Looked into this a bit further.
When it starts the heat pump runs for just about 1 second then the tap light flashes indicating a fault.
I connected a spare motor to test and it still does the same.
The door interlock and floor light works.
I get continuity through the inlet valve.
This model does not have a heat exchanger valve.
The machine doesn’t take any water so the reed valve doesn’t operate.
Float switch operates correctly.
There’s continuity through the salt regeneration valve.
There’s no visible damage to the PCB.

Have I missed anything?

[electrofix]

open circuit or jammed drain pump ?

Dave

[Twoten]

electrofix wrote:open circuit or jammed drain pump ?

Dave

It’s definitely not jammed, I don’t think I checked to see if it’s O/C though.
I’ll go back and check this.
There can’t be much else left other than the PCB.

[electrofix]

as you know bosch tech is hard to get but the nearest one i can find is

https://www.manualslib.com/manual/958098/Bosch-She4am12u.html

its worth scanning for any possible clues as it uses 3 phase motors etc

Dave

[Twoten]

electrofix wrote:as you know bosch tech is hard to get but the nearest one i can find is

https://www.manualslib.com/manual/958098/Bosch-She4am12u.html

its worth scanning for any possible clues as it uses 3 phase motors etc

Dave

Cheers Dave.

[Twoten]

Just to update:
Further testing revealed the drain pump to be open circuit.
Pump replaced and problem resolved.
Considering the number of Neff and Bosch dishwashers I’ve looked at, I’ve never found one of these pumps go open circuit.
Thanks for the help.

[Author]

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