LG LDF7551ST Drain Error

[hamhock75]

I thought I would share with others what I experiences with this LG model.

The first drain error occurred because of a failure with the drain pump under load. I used the self test feature to test the speed of the drain pump with no load. It worked fine with a reported speed around 320 rpm. I then poured a few cups of water inside and ran the same test. The pump then failed.

Next I made the mistake of acquiring a non-OEM replacement drain pump. It worked but now I had an intermittent drain error even though the dishwasher actually did drain.

I measured the coil resistance of the three windings of the drain pumps three phase motor. The OEM pump measured 4.5 ohms on all three windings, the non-OEM pump measured 6 ohms on all three windings. A 33% discrepancy.

I ordered an OEM drain pump. The pump came in this past Saturday. The coil resistance of the new pump also measured 4.5 ohms exactly the same as the old pump.

Now there are no more intermittent drain errors.

I suspect the LG can sense the current being drawn by the drain motor. If it is sufficiently out of spec, the drain error gets set.

Lesson learned, avoid "almost fits" non-OEM parts.