co-pilot seat air cylinder

[putneyflash]

My right hand seat slides back and forth and does not lock into the
desired postion.It appears that the cynlider retracts but will not
come back out to engage the seat. When the switch is pushed does the
air push the cylinder in? and when the switch is released the rod
should come back out by spring pressure?. I see two "o" rings, other
than that I don't see much to go wrong. Ant thoughts??
Thanks for all your help.
re brake 1983 FC_35 sb