dishwasher residue/film/dust

[trae]

wdt780saem1. problem started a few months ago. there is a very fine brown/black dust evenly coating the inside of the washer and on dishes.

upstream - i have checked the water coming into the washer. all wipes come back clean. i feel relatively confident it is not an iron problem. we are on city water and see no evidence of iron problems in any other areas/appliances. if it were iron, all residents would be having this problem.

downstream - i have checked drainage. there does not appear to be anything regurgitating back into the washer. the drain line is opaque and i don't see any obstructions. the valve appears to be working correctly. i have removed and inspected drain pump. all clean

that leaves something in the washer itself. i see no evidence of worn/compromised parts. i removed main pump. all wipes come back clean. heating element is clean. i have cleaned all parts inside several times. all wipes inside tubing/wash arms come back clean. it is something happening after the water is sprayed and before it drains. we have run numerous cycles with dishwasher cleaners and no dishes. there has been no metal such as cookie sheets.

i am absolutely baffled. this dust/residue/film appears to be coming from nowhere. it costs $100 just for someone to step into our kitchen. then labor and parts. we can almost buy a new one for that much. i am troubleshooting the problem because i feel like it can be solved relatively easily if the root cause can be found.

 

[trae]

i appear to have either 2 different problems or 1 problem with 2 symptoms. i started a load on heavy setting with a different detergent. when it completed, the soap was not completely dissolved from the dispenser, the dust was present and there was a bit of soap residue scattered on the bottom of the tub. i ran another cycle and the soap was still not completely dissolved from the dispenser nor the bottom of the tub.

the wash arms do not appear to be clogged so the only thing i can figure is that the main pump is not effective. it's just not pumping water strongly enough to clean the inside of the tub. i can't think of another reason for 2 cycles to not dissolve the detergent.

[Vance R]

Since you haven't mentioned it the filter screen has to be clean. You should be able to see through it.  The inverter style motor in this dishwasher usually stop running, guess it could be intermittent?

[trae]

thanks for the response. filter is spotless. has been cleaned multiple times. water in the sump is free of debris

there definitely is splashing. i can hear it and feel it against the top of the tub. however, i don't know if there is enough force or if there is any arm rotation. i disconnected the wash arms and sprayed each nozzle with the jet setting on my outdoor hose sprayer. then i removed the sprayer and held the hose up to the inlet on the wash arm. the nozzles appear to be open and the arm did rotate. i'm going to try another cycle in case i knocked some junk out of the wash arm. i'm starting to wonder if the wash arms are just poorly designed because this dishwasher has not cleaned well from the time we bought it.

after restoring the wash arms, i cleaned thoroughly again and ran another cycle. the black dust is starting to show up again and very lightly soiled dishes were not clean. absolutely baffling. the wash arms and the pump are used in multiple dishwasher models. i wonder if the circulation pump is not getting enough voltage. i have a multimeter. how can i check and what should i be looking for?

[Vance R]

Pull the door panel and on the module connector P5 pins 1 & 2 has light blue wires. Should be 120 vac when wash motor is running. The tech sheet should be in the toe plate, trying check for error codes.  This model has a diverter to control water flow to each spray. It will wash with bottom arm then the mid level and top arms. usually you heard when it changes arms.

[trae]

the latest in the saga:

the circulation pump has basically stopped working. i don't know if it has been failing for some time or just quit suddenly. it seems to have proper resistance and is getting 120v during cycle so i think the problem is mechanical.

oddly enough, diagnostic mode returns service error codes f5e1 (door) and f7e1 (heating element). what i don't know is if those are codes from a prior error state or if the washer thinks those are current error conditions. the door is definitely working correctly and the heating element seems to be fine. the customer error codes are f-e- which i think means no error.

i don't know if replacing the circulation pump will solve both symptoms.

[Vance R]

The wash motor is a inverter style and seems to fail often.  At the moment it is the major failure. Not sure if it will solve both problems as well.