Samsung dishwasher Model DW80M9960UG Distributor cam adjustment

[Robert Hiebert]

I have a Samsung dishwasher Model DW80M9960UG that is getting rejects. The only area of the DW that cleans properly is the lower left basket, all other areas will have rejects. I have been able to put it into diagnostic mode and no trouble codes are generated. The water wall reflector appears to be operating properly. The symptoms seem to be what would happen if the unit was in "Zone Booster" mode, but the problems are constant no matter what cycle is selected. I am suspecting that the distributor valve is not rotating and is stationary in the "Zone Booster" position which directs water to the lower left nozzles only. I have the service manual for this model and in the troubleshooting portion it mentions that a possible cause would be that the cam that operates the microswitch on the distributor motor assembly could be out of adjustment, but I could find no place in the manual that states how this adjustment is made. I removed distributor motor assembly, which consists of the gear motor and microswitch. I bench tested them and they both operate correctly. The cam that operates the microswitch is on an intermediate shaft that is driven by the gear motor. This shaft is keyed to a gear that is the first gear in a gear train that operates the valve itself. The second gear is just an idler. The third gear is part of the valve itself. The gear motor operates CCW at 3 RPM. The valve operates in the same direction and speed. The valve has to be indexed to the cam correctly in order for the controller to correctly determine the position of the valve. Can anyone tell my how I can confirm that this relationship is correct?

[Vance R]

From the looks of the manual "adjust" is probably a poor translation. They are probably talking about something block in the disc. If step 3 for the position switch and step 5 for motor power are good the distributor is probably ok. 

[Robert Hiebert]

Thanks for the reply, but I really don't quite understand what you are saying. The cam has 3 "lobes". Two are quite pointed and are about 90 degrees apart. The third one has a long duration of about 90 degrees. The centre line of the long one and the mid point between the two pointed ones are opposite each other. The rotary distributor valve has 4 distinct passages that appear to be 90 degrees apart. The first passage directs water from the circulating pump to the upper and top spray arms only. The second directs water to both arms and the left lower nozzle. The third directs water to the left lower nozzle only. The forth directs water to both lower nozzles only. There are no marks on the gears that would indicate how they should be positioned so that the valve position can be determined by the cam position. 

[Robert Hiebert]

Update:

I assume that the valve and limit cam must be indexed together to sent the correct signals to the controller but I don't see anything obvious on the gears to indicated this. The service manual mentions that a possible cause of improper operation could be the cam out of adjustment, but I don't see any reference of how to check this adjustment. Because I don't know what the controller expects to see and what it does when it sees it, I just made and educated guess and re-assembled it the way I thought it might go.

So far it looks like my educated guess is working. The last load came out good everywhere. I reasoned that the only unique place on the cam that the microswitch roller could be positioned would be in the valley between the two pointed lobes. The most unique place for the distributor valve would be where you could see the port open to the upper and top spray arms before the spray manifold was installed. If this last load was just a one off I'll report back, but in the mean time I'll call this one fixed.