My viking dishwasher does not rinse the soap scum off the dishes

Maybe . . . remove the lower rack and invert it. Look for cracked or missing plastic coating, exposed, rusted & possibly "swollen" inner steel rod/wire. If found, remove the upper rack and look for more of the same. What you think is "soap scum" is probably rust and other iron compounds leached by the dish soap out of the rusted steel onto the dishes and the dishwasher interior. The following worked for me . . .

To clean the interior (with both racks removed), set to "No Heat" dry, then "Pot & Pan" wash and allow to fill. Open door, dump in a bottle of "Lime A-Way", close & latch door and allow to complete cycle. This should remove most rust and iron-sulphate deposits from interior. If not, scrub them with Lime A-Way and a ScotchBrite pad, then cycle again.

Racks must be replaced (Viking are very expensive, Asko, Bosch, or other lower racks may fit: check your neighbors' racks for fit), upper rack must be Viking unless you can exact-match the Asko or Bosch equivalent.

Possible fix: remove the loose plastic coating and flaking rust with a knife, ruff plastic coating with ScotchBrite, clean with rubbing alcohol, then treat metal/rust with "rust converter" (hardware or home imp store), wash with soapy water, rinse, then clean with rubbing alcohol, dry fully, coat with "high temp" (orange or yellow) silicone sealant (auto part store), covering exposed metal and a half inch or so over the plastic coating. Let set for a day or two.

A trip through the dishwasher for all your stained stainless, glasses and non-metallic coated or non-metallic decorated dishes with Lime A-Way as above (on new or "rebuilt" racks) should get the metallic scum and rust off them.

Its not soap, its actually calcium from hard water. There is a new product out at www.dishwasherfilter.com that solves this problem once and for all. It is a small filter that goes under the sink and filters out the hard minerals that cause these spots from the water before they enter the dishwasher. It is very affordable (like 70 bucks) and even has a money back guarantee. After just one load you will be amazed how your dishes look.