Trailer Suspension System Components and General Maintenance Guidelines HEIGHT CONTROL VALVE - The height control valve on the trailer air sus-pension automaƟcally responds to the relaƟve posiƟon of the axle and vehicle frame. It meters air into or out of the air springs. VariaƟons in load or temperature only affect the adding or exhausƟng of air. The trailer air suspension is a mechanically stable suspension, only one height control valve is necessary.
Suspension Height Control Valve When the actuaƟng lever of the height control valve moves up, the valve opens and connects the air supply to the air spring. When the actuaƟng lever moves down, the valve shuts off the air supply and opens the ex- haust port to vent excess air from the air springs. A check valve prevents the loss of air spring pressure if the air supply fails. In the central posiƟon, air does not flow in or out of the air springs. RIDE HEIGHT ADJUSTMENT 1. Connect the vehicle to a compressed air supply with approximately the pressure of the normal sup- ply system. 2. Ensure the inflaƟon of the air springs. 3. Measure the ride height by using this method: a. Measure from the underside of the trailer frame to the top of the axle as shown in figure 24 below b. Add half the diameter of the axle to the measurement
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