224 Lifting ArmsAdjusting Up/Down Holding Valve PressureNOTE: The up/down cylinder on a standard lifting arm has no holding valve on it. However, it has apressure relief cartridge that provides stroke-end cushioning during extension of the cylinder.The up/down cylinder on a HD lifting arm is fitted with a holding valve as well as a cushioningadjustment screw which is used to adjust the stroke-end cushioning during extension/retraction of the cylinder.NOTE: If the cushioning effect needs to be adjusted, simply turn the cushioning adjustment screwaccordingly: clockwise to increase cushioning effect; counter-clockwise to reduce it.To adjust the up/down holding valve pressure:1. Apply all safety measures to ensure safety around the vehicle at all times.2. Make sure that the parking brake is applied.3. Locate the holding valve on the up/down cylinder (see Figure 10-20).4. Connect a pressure gauge to the automated arm valve.Figure 10-19 Quick coupler for pressure gauge5. Start the engine and engage the hydraulic pump.6. Using a lever on the valve, manually raise the Right Hand™ arm gradually.7. If the gauge does not indicate a pressure of about 700 psi when the automated arm starts goingdown, adjust the up/down holding valve adjustment screw to set the pressure properly.NOTE: Turn the screw counter-clockwise to increase pressure or clockwise to reduce pressure.NOTE: This pressure value of 700 psi is a reference value; it could be more or less. It all depends onhow much pressure the up/down holding valve needs to resist to a downward pulling force ofat least 1000 lbs.
