Help needed how to rebuild Am Standard B200 shower mixing valve

[Seekr2]

I was able to find a rebuilding kit for this 55+ year old shower temperature control. Looks like the photo posted by mclintock Feb 17, 2014). Two, kits, in fact, since I can't see beyond the tile cutout to see if I need the 1/2 inch or 3/4 inch kits. But there are a LOT of parts and washers and seats. Can't find an instruction sheet or adjustment manual. Will this all spring apart when I take the cover off, or will it be possible to replace the parts without instructions?

The mixer control handle control was Shut>Cold>Hot. Shut didn't completely stop the flow. A second, conventional valve before the shower head controls the flow. There are six other shower heads. The problem was that once the flow was set by the second valve between the mixer, the flow would gradually diminish to a trickle. Turning the valve for more flow was OK - until the wall piping suddenly started to vibrate violently, until flow was quickly reduced. Didn't matter whether hot/warm or cold. Removing the cover plate showed a tiny leak from the cover. (If I do get it rebuilt, is it recommended to put sealant on the 3-inch diameter cover gasket - the strip is only about 1/8" wide)

I received both AS107 (3/4" valve) and a 12936-07 (1/2" valve) rebuilding kits from NY replacement parts on the web.

Any help regarding this project would be most appreciated!

 

[Marlinman]

From the looks of your photo you have the 1/2" R1400 valve using the 12936-07 kit you purchased. There are no hidden surprises when disassembly. Carefully look at the hot and cold plungers since they are different.