KitchenAid KDI-21AD not cleaning well - troubleshooting tips?

[GoJohnGo]

I have a KitchenAid KDI-21AD Dishwasher that worked great for 18 years while I lived in the house, but my tenants have been complaining that it's not washing well. Checking it out, it did seem to be dirtier in the bottom than I remember, and I found that the lower Wash Arm Support filter material had completely dissolved (see picture). I've been lucky to find a replacement Wash Arm Support, but I'm not sure whether this is actually the cause of the dish cleaning problem. For this dishwasher, what other parts should I be checking out, and how do I go about troubleshooting?

I'm reasonably mechanical, but am not familiar with dishwasher innards.

 

[rp2813]

For sure the missing fine mesh filter has a lot to do with poor performance. 

 

Are any of the outlet holes in the wash arms clogged?  Is the hole in the bottom of the lower 4-way wash arm plugged?  That hole is what keeps the filter clean.

 

Is the machine filling with enough water?  It should fill enough to just cover the heating coil.

 

Another thing to take a look at is the check valve.  It's located on the end of the drain hose where it connects to the pump.  If the valve is stuck open, it can reduce the flow of water from the pump to the upper/top rack wash arm, perhaps enough to prevent the arm from rotating.

 

It's easy to remove the valve.  To check it for proper operation, try to blow through it from the drain hose end.  If you can't blow through it, the valve is OK.  If you can, it's stuck open and needs to be replaced (at least I think that's how it's done).  The part is NLA from Whirlpool, but GE part #WD1X1486 will work.  It's just a rubber flap.  You'll have to open up the valve housing to do the R&R.

 

Also check the flexible sleeve at the rear of the upper wash arm's supply tube.  If it's cracked it will likely leak under pressure, maybe enough to compromise wash arm rotation.

 

Is that some broken glass I see in the sump area under those two blue tabs?  If there's glass lodged in the pump it could be impeding performance.

 

Do the users know how to properly load a dishwasher and are they running the hot water at the sink to bring it to temperature before starting the machine?

 

Looks like the components in the picture would benefit from a treatment with LemiShine once you have everything back together.

 

[washer111]

That hard water staining may well be an indicator that the owners have been pre-rinsing the dishes, causing the detergent to attack the wash-arm support and mesh filter.
I dunno whether John (Combo52) will chime in - but this is something I see mentioned regarding the wash-arm supports: Pre-rinsing may cause premature failure.

Check the machine is filling*, ensure they run the tap hot beforehand AND are using an appropriate cycle for their soils and suggest using some STPP in there to boost performance if the washing performance isn't up to snuff.

*The water valve may be clogged or obstructed. It would probably be worth using a "known good" spare to see if this improves the fill.
An old water heater may also be the cause.

 

[GoJohnGo]

Thanks for the help!

Ok, so the water inlet valve may be obstructed, causing the tub to not fill. Definitely a possibility. Occasionally, our well has issues and the pump puts sand in the lines. I had to replace the inlet valve for the clothes washer, so this is definitely suspect.

Also, it sounds like the check valve may allow the tub to drain prematurely.

I assume I can check both of those by starting the machine, running it through the fill cycle, then open the door and check the water level and whether it's dropping.

I'll also check all the holes in the washer arms and make sure they're clean.

I'll also check the upper wash arm sleeve for cracks.

I didn't know that there should be hot water at the sink before starting the cycle; I'll convey that message.

And lastly, I'm surprised that pre-rinsing would cause a problem. I've always done it and assumed it would reduce the load on the washer! I'll have to read up some more on this.

I'll report back soon...