I found this diagram. Looks like there is supposed to be only
one switch.
The object at the top of the drawing, just left of center, looks to be a simple junction "tree". If that is true then it can be cleaned and tested for leaks, and if broken, replaced with one pass-through and two tees. If there are check valves integral and they are not working, they can be replaced with remote ones.
Once you locate that tree, it should be a simple process to test hoses for leaks and operators for function using a simple hand held vacuum pump.
