One of the most common technical support calls VAC gets on our V100 and V200 is when no input signal or very little input signal is given to the positioner and then the valve package will open. There are 2 possibilities that we need to explore to get our positioner to operate correctly.
One is tubing, when we turn on the air with no input signal air will be exhausted out of the C- port. So if we are at close and our tubing is backwards, the air going out of C- will cause the valve to open and the control signal if ever turned on will have absolutely no affect on the positioner. To fix this problem we must first put the valve where it is desired to be at 0% input signal. Then turn off the air, and finally swap the C- and C+ tubes around. When we apply air back to the positioner the valve package should not move.
The second occurrence is when the cam is not on tight. We must make sure when we loosen the cam nut to mount the positioner, we must then remember to set the cam properly per the IOM of the V100 or V200, and then tighten the cam nut first then the tighten the locking screw. If the cam nut is loose the positioner will go to full open this may happen either when a slight input signal is given or at 0% of input signal, then the valve package will go to 100% it will not stop in between. To fix this we must put the valve back at desired position at 0% input, then turn off the air, set the cam, and finally tighten the cam nut and locking screw.
Our VAC website has a section called Technical Quick Help. Please take a look and as always, if there is any issue, call us at (205) 678-0507. The worst problem that we have are the problems we do not hear about.