by Foretravel
Most of the time when the cylinder is tested, it is only tested in the out or (closed ) position. This is not a proper test for leakage. The cylinder must be tested in both the out (closed) and in (open) positions.
Note: To test the cylinder in either position you must have full system pressure (120 PSI).
Testing can be performed fairly easily in the out (closed) position by finding the seal end of the cylinder in the boot located under the step cover, and leak tested at that point.
To test the in (open) position the clevis that attaches cylinder rod to the step cover must be disconnected, to allow the step cover to be pulled out and then the rod retracted to simulate the in (open) position and tested for leaks. If there are leaks detected in either position the cylinder must be replaced.
The air control valve also must also be checked while the step cover is in both the in and out positions. This valve is located at the rear exterior of the fold-out step cavity. The valve can leak depending on the position of the cover. Many times the valve can leak and never be diagnosed because it was not checked in all operating modes.