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Ride Height Adjustment Instructions
NOTE: The following procedures require the vehicle to be parked over an inspection pit or level surface and
may require two people working simultaneously when using a two HCV system.
7. Bring the suspension to the vehicle manufacturer's recommended ride height. Ride height is measured
from the bottom of the frame rail to the center of the axle. Refer to the vehicle or suspension manufacturers
manual for proper ride height measurement.
8. With the suspension at ride height and the HCV control arm at center position, determine the location of
the lower linkage tab. A typical PR HCV and linkage assembly are shown in Fig. 5. Note the recommended
angles between the HCV and linkage connection before installing the bottom linkage tab.
9. Damage to the valve, linkage and other suspension components may result if the recommended angles
are not followed. Measure the distance from the control arm linkage mounting hole to the axle tab bracket
mounting hole (Dim. "A" - Fig. 5). This is the required linkage length.
10. Connect the linkage to the control arm and axle tab bracket. For correct linkage assembly consult the
suspension service manual.
IMPORTANT: Adjustments to the suspension ride height requires system air pressure. Adequate system air
pressure must be maintained throughout adjustment procedures.
11. CHECK FOR PROPER RIDE HEIGHT. Disconnect the lower linkage end from the axle tab. Lower the control
arm and linkage about 1" and hold for 15 seconds to lower the suspension. Reconnect the lower linkage end,
the suspension should return to ride height. Measure the ride height on both sides of the vehicle to verify that
the suspension is within the manufacturer's specified tolerance.
12. FINE ADJUST RIDE HEIGHT IF NECESSARY. Carefully adjust the linkage assembly or control arm to bring
suspension to ride height. Your PR or PR Plus HCV may have an adjustable control arm which provides
approximately 1" of ride height adjustment. After each adjustment of the linkage or control arm repeat
previous step. This may require several attempts, repeat until proper ride height is obtained twice in a row.
NOTE: When using the adjustable control arm to make fine adjustments, torque bolt to 25-30 in-lbs.
FINAL CHECK. Soap spray test all air line connections for air leaks and verify that all fasteners are tight.
NOTE: Ride heights may vary slightly from the loaded to the unloaded condition.
NOTE: The vehicle should maintain air spring volume and remain near ride height during short periods out
of service. An air suspension system can deflate during extended periods out of service.
NOTE: A small amount of air may escape from the exhaust located under the interface cap; this is normal
and should not cause alarm or require replacement of the valve.
NOTE: If two valves are used on a chassis, then the valves must be located in the same position and location
on each side of the vehicle. Proper installation of a 2 HCV system is required to ensure the air suspension
system operates correctly.
Check For Linkage Interference
NOTE: The following procedures require the vehicle to be parked over an inspection pit or level surface and
may require two people working simultaneously when using a two HCV system.
13. CHECK LINKAGE(S) FOR CLEARANCE. Disconnect the lower linkage connection and move the HCV control
arm down to fully exhaust the suspension. Reconnect the lower linkage to verify linkage does not interfere
with frame rail, electrical wiring or air lines. If there is linkage or control arm interference, the valve position
and/or linkage axle tab need to be moved.
Check For Linkage Interference
(continued)
14. CHECK LINKAGE OPERATION WITH SUSPENSION AT FULL EXTENSION. Disconnect lower linkage from
axle tab and move the HCV control arm up to raise suspension to full extension.
IMPORTANT: DO NOT continue to inflate air springs after full extension is reached. Damage to shock
absorbers and/or air springs could result.
Immediately reconnect lower linkage to axle tab. Verify the control arm/linkage connection rotates smoothly
and is free of tension. If the linkage is in tension or the rubber link end is being pulled along the rod at full
extension, the valve position and/or linkage axle tab will need to be moved.
Lowering/Exhausting Your Air Suspension
Certain applications may
require that a vehicles air
suspension has the ability
to fully lower or exhaust
the air springs from ride
height. The PR Plus HCV
has the option of an
integrated Normally Open
or Normally Closed dump
valve. The Normally Open
dump valve is typically
operated in conjunction
with a manual switch or
electric solenoid valve
as shown in Fig. 9. The
Normally Open dump valve
Figure 5
allows air to be exhausted
from the air springs when
a pilot pressure is applied.
The Normally Closed valve
is typically operated from
the gladhand or emergency
brake line as shown in
Fig. 10. The Normally
Closed dump valve allows
air to be exhausted from
the air springs when the
pilot pressure is removed.
It should be noted that the
optional dump valve for the
PR Plus HCV is NOT sold
separately and CANNOT
Figure 6
be replaced in the field.
The Haldex Pilot Valve, part number 90554615, can be used in conjunction with the PR HCV to provide
air suspension exhausting. The Haldex Pilot Valve provides the capability to exhaust air from any air
suspension in a Normally Open or Normally Closed operation.
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