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So I’m now thinking this is definitely some kind of overheating issue with the drain pump.
On my Bosch it’s this part: https://shop.ukwhitegoods.co.uk/423048-dishwasher-drain-pump and having removed it I can see it’s basically an electromagnet coupled to a magnetic rotor. One of the coils on the electromagnet has a thermal cut-out device bonded to it and I suspect this may be the issue – there is some form of electrical fault that manifests as the pump overheating, causing the thermal cut-out to trip. The pump then fails to drain, and the dishwasher floods following the main wash cycle when it tries to refill for the rinse.
After it has flooded, if I leave the machine switched off for a few hours the pump cools down and the thermal fuse resets. Switching on again, the pump activates (because the float valve is raised) and drains the machine. I wonder if you have to switch the machine off to get it to cool down because otherwise the safety system that is designed to prevent flooding is constantly trying to run the pump, so it keeps re-tripping the thermal cut-out?
The other possibility in all this is that there is a loose electrical connection at the pump which only manifests when the pump is hot. I see that the enamelled wire that makes up the coil is bonded to the spade connectors (and the thermal cut-out) using press-fit connectors that rely on an integral knife-blade cutting through the enamel to make contact with the copper. So it’s quite a small connection area that could be subject to corrosion and then a bit of overheating could create a break in the circuit. So I’ve tried effecting a repair by redoing these connection on a fresh piece of the enamelled wire – we’ll see if it holds.
Anyway, I’ll probably try fitting a replacement pump at this stage.
Thanks Dave,
Yeah, I wondered about it being the jug impeller but I don’t hear it doing the continual filling/emptying thing so I’m not sure. Might be worth doing anyway just to rule it out though…
Update: Today I ran a cycle with just a cleaning pod. The machine did not explicitly flood (check water light did not go on) but at the end of the cycle when I opened the door there was a lot of water in the bottom, enough for the float valve to be activated. I pushed the float valve up and down but the pump failed to start. So I closed the door, turned the dial to reset, and waited to see if it would empty. No joy, pump still would not run. Turned it off and on, whereupon I got three flashing lights (check water, refill salt, refill rinse aid). Still no pumping. I turned the dial to a regular program and waited to see if it would pump out as a preamble to starting the programme. No joy, after a few seconds it started filling so I turned it off.
About an hour later I cam back for another try. Again the three flashing lights when I turned it on and selected the reset program. But this time, when I turned the dial to a regular program, I heard the drain pump start to run. So I selected the reset program again and this time the drain pump ran and emptied the machine.
From all of this I feel I have either a control board issue or some kind of temperature sensitive drain pump problem.
What do you think?
