We have one 6890 GC (G1540A), which has not been used for a while. The GC has 2 6-port valves, which are configurated for gas sampling and switching. The actuator driven by compressed air for these two valves does not seem to work well. Sometimes I heard about the air leaves from the outlet of the solenoid valve. Does this mean the valve has defect or is there any other problem to cause this? In addition, when we tried to operate the valve from the chemistation software, the actuator and/or valve have no response to the software. Anyone knows what the problem is for our GC? Thanks so much!