psfred,
My Catalog "B" shows the two o-rings, one just above the water outlet and another smaller 0-ring just below the outlet, or a total of four o-rings for the split heating system. Top o-ring makes sense (seals top plate), bottom o-ring doesn't (I wouldn't use an o-ring for a shaft packing seal but I guess you never know). Catalog also shows a strange clip like thing just to left of control valve's left fire wall mounting hole. Haven't had one apart and catalog doesn't show exploded view but I can't imagine anything more complicated than two butterfly valves in a common housing. Give us the run down when you get it fixed.

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daBenz - 1970 220D