I don't know the specifics of that valve. Somebody here probably does. But, on some, all you need to do is remove the handle and rotate the cartridge 180-degrees and that reverses the operation. The red disk is part of the anti-scald mandate. It is adjustable. Some turn, some you have to pull out and reinsert. This probably didn't help all that much, but it probably can be returned to 'normal' operation quickly and easily with the right instructions...hold on. You could also call American Standard on Monday...they should be able to point you to the instruction sheet or talk you through how to do it if someone here doesn't help first.