ber of the governor. The more common cut-out pressure
is 862 ± 35 kPa (125 ± 5 psi).
With the engine still running make a series of brake
applications to reduce the air pressure and observe at
which pressure the governor cuts in the compressor. As
in the case of the cut-out pressure, the cut-in pressure
should be in accordance with the governor piece
number. Common cut-in pressure is 690 to 717 kPa
(100 to 105 psi). Never condemn or adjust the governor
pressure settings unless they are checked with an
accurate test gauge or a dash gauge that is registering
accurately. If the pressure settings of the governor are
inaccurate or it is necessary that they be changed,
procedure is as follows.
First, unscrew the cover at the top of the
governor. Next, loosen the adjusting screw lock nut,
With a screwdriver the adjusting screw is turned
counterclockwise to raise the pressure setting and the
screw is turned clockwise to lower the pressure setting.
After the adjustment is completed, the adjusting screw
lock nut should be tightened to lock this adjustment.
NOTE: 1/4 turn will change the setting approximately 28
kPa (4 psi). Any governor requiring more than a 360°
adjustment should be cleaned and inspected.
Leakage checks on the D-2 governor are made
at its exhaust port in both cut-in and cut-out positions. In
the cut-in position check exhaust port for inlet valve
leakage by applying a soap solution at the port. Leakage
could also be past the bottom piston grommet. In the
cut-out position check the exhaust port to determine
leakage at the exhaust valve seat or stem grommet. In
this position leakage could also be past the upper piston
Leakage in excess of 25 mm (1 in.) soap bubble
in 3 seconds is not permissible in either of the foregoing
tests. If excess leakage is found, the governor must be
repaired or replaced.
Apply parking brakes or block wheels to prevent
vehicle from moving.
Drain air brake system.
disconnect reservoir air line. If remote-mounted
governor, disconnect both the unloader and reservoir air
If compressor-mounted type governor, clean mounting
pad on both compressor and governor block. Clean
connecting line or lines. Also be sure compressor
unloading port is clear and clean.
If the governor is being mounted remotely, it
should be positioned so that its exhaust port points
down. It should be mounted higher than the compressor
so that its connecting lines will drain away from the
If compressor-mounted type, use a new
governor mounting gasket.
Connect air lines to governor. Test governor as
outlined under SERVICE CHECKS.
Clean governor exterior of road dirt and grease
using a good cleaning solvent and brush.
Unscrew the top cover.
With a pair of retaining ring pliers remove the
spring assembly retaining ring.
Remove the adjusting screw and spring
Remove the lock nut, then the hex-shaped upper
spring seat from the adjusting screw.
Remove the pressure setting spring, lower
spring seat, spring guide and the other lower spring seat
from the adjusting screw.
Remove the exhaust stem and its spring from
the top of the piston.
With the body in the inverted position tap it lightly
and the piston should fall out.
Remove the inlet and exhaust valve spring and
the valve from the piston.
Remove the two piston grommets and with a
hooked wire remove the exhaust stem grommet.
Clean or remove the unloader and reservoir port
CLEANING AND INSPECTION
Clean all metal parts in a good cleaning solvent.
Wipe rubber parts dry.
Inspect body for cracks or other damage. Be
particularly careful that the body air passages, the filters,
exhaust stem and piston are not obstructed.
Check springs for cracks, distortion or corrosion.
Replace all parts not considered serviceable
during these inspections.
PRINTED IN UNITED STATES OF AMERICA
CTS-4097A - CHAPTER I