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I have a Miele Dishwasher G2872 SCVi. Lately, it has started to beep and shows “Technical Fault F78” on its display about 4-5 minutes into the wash cycle. Miele Tech Support say F78 means a fault with the circulation pump. Did some initial checks - it looks like the water is draining out without problems and fresh water is coming in too. The filter is clean, and there appears to be no blockage in the circulation pump (I can move it easily by hand). Any thoughts on what might be the issue? Is there any other remedy that one can think of (apart from buying a new dishwasher of course)? Thanks.
Usually the impeller comes apart in two pieces. The dishwasher detects low pump pressure, stops the wash, drains the water and ends the wash programme with F78 error. You need to glue the pump impeller with special industrial adhesive and leave to set for 24 hours, you also need to take it apart, don’t glue it in place. Made a video about it, search youtube for f78 miele impeller diy. Miele wants 400eur for a new full pump, for older models there is a repair kit.
I had to do a hard power reset! Turn the power off for 30 sec min.
Things that have worked for me with f78 error: once; took bottom spray arm off and poured hot (not boiling) water down hole, this cleared a blockage. Many times; drained machine and examined grill over channel at back, if this has anything at all in it, eg tiny hairs, clear plastic, eggshell, get it all out - a cake fork works quite well, the machine should then work. When the machine activates its pump it looks for a current down the channel at the back and shuts off with f78 if it doesn’t detect one. Small obstructions in the channel can obstruct the current and make the sensor think the pump is not working. This is a design flaw with this machine as the plastic grills over the channel are insufficient to stop things getting through them, and may make things worse because thin strips etc can drape over them and are then impossible for the machine to dislodge itself. Update (04/30/2022) the ( most frequent) problem which causes this fault in my machine is a blockage in the pump sensor channel. With the machine turned off and the racks, spray arms, filter etc, taken out, drain the broken machine as much as you can, using ladle or small container. You can see a channel covered with white grill bars at the back. This is the channel that takes the current of water from the pump to the sensor that tells the machine that the pump is working. Examine the channel carefully, you may need a torch. If you can see anything at all in this channel or draped over the white grill bars, then you need to get it out, in my house our smallest forks are the right width to fit between the grill bars. Once the channel is clear put the machine back together and restart it, the error should have cleared and the machine’s cycle should work without F78. The second most common problem, but much less often is a blockage. If you have checked the pump chamber and it is clear then try pouring hot (not boiling) water down the bottom spray arm hole, it should come out and fill up the bottom chamber. If the water backs up and then goes through in a rush you have cleared a blockage. Be aware that the water in the bottom of the machine will now be very hot. If blockages in the sensor channel or elsewhere are happening it means that residue is getting though the machine’s filter. Make sure the filter and stainless steel mesh are clean, and there is no residue on the plastic where the stainless steel mesh sits which might be stopping it sitting flush against the bottom of the machine. You may also want to clear very heavy residue off pots etc before putting them in the machine. My wife tells me I don’t do that very well, which is why we only ever get this error when I have stacked it.
The main problem I had was defect impeller in the circulation pump. The upper part had loosened from the base. I glued it back on with epoxy, and the machine worked again for some months until it happened again. I glued it again, and it worked for some weeks. A better glue would have been better. But the real problem is (was?) the quality or method of attaching the two impeller parts together. Since the machine was 12 years old, the replacement punp would cost more than a new machine, so no a new machine is in place. (I also had a problem with the water supply (valve stuck in closed position with handle in open position), and with latch mechanisms in the circulation pump assembly stuck by the o-ring du to poor reassembly after I had opened it. Discovered and fixed.)
