I had the same problem, i saw this forum, i also tried with oil and boiling water, it didn't help, then i saw a german disassembling the Circulation Pump, i disassembled the machine, i removed the pump, i disassembled the pump, one of the sectors that is responsible for changing between the good water and the used one was with residues, which didn't seem normal to me, i cleaned everything, lubricated it, assembled it inside the machine, it started working, it wasn't easy at all, but it saved me from buying a new pomp which is expensive.
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I had the same problem, i saw this forum, i also tried with oil and boiling water, it didn't help, then i saw a german disassembling the Circulation Pump, i disassembled the machine, i removed the pump, i disassembled the pump, one of the sectors that is responsible for changing between the good water and the used one was with residues, which didn't seem normal to me, i cleaned everything, lubricated it, assembled it inside the machine, it started working, it wasn't easy at all.
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It only worked once and again the same F78, again I disassembled the machine, before disassembling the pump, I noticed that there were bits of grease(or bits of anything) in the used water reservoir, I assembled the machine, heated the water, poured several liters of boiling water into the machine, waited a few minutes, unplugged it, plugged it back in and it started, I put it in the most powerful mode at 70ºC to see if that grease (or bits of anything) would come out of the reservoir, for now it works.
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One of the things i was told to do when i bought the machine was to put the strongest mode with empty machine to work to clean the machine some times, I never did this, hence the possible malfunction.
The video of the German dismantling the pomp is here if anyone wants it.
I had the same problem, i saw this forum, i also tried with oil and boiling water, it didn't help, then i saw a german disassembling the Circulation Pump, i disassembled the machine, i removed the pump, i disassembled the pump, one of the sectors that is responsible for changing between the good water and the used one was with residues, which didn't seem normal to me, i cleaned everything, lubricated it, assembled it inside the machine, it started working, it wasn't easy at all, but it saved me from buying a new pomp which is expensive.
The video of the German dismantling the pomp is here if anyone wants it.
Miele Geschirrspüler Umwälzpumpe zerlegen + Wasserweiche einstellen + F78 F79
https://youtu.be/yiuzdwnSaFM