BENDIX SD-06-1600 Manuel D’Utilisation

To describe the operation, we shall assume that the low 
pressure indicator is set for 60 psi. When air pressure at the 
supply port and under the diaphragm is above 60 psi, the 
electrical contacts remain open because the force exerted 
by air pressure underneath the diaphragm overcomes the 
force exerted by the spring above the diaphragm.

When air pressure below the diaphragm drops below 60 
psi, the spring exerts a force which is greater than the 
force exerted by the air pressure below the diaphragm. 
This causes the diaphragm (and the piston in the Bendix

®

 

LP-3

™

 indicator) to move and allow the electrical contacts 

to close. This completes or closes the electrical circuit to 
the warning device, warning the driver of low air pressure 
in the system.

Important: Review the Bendix Warranty Policy before 
performing any intrusive maintenance procedures. A 
warranty may be voided if intrusive maintenance is 
performed during the warranty period.

No two vehicles operate under identical conditions; as 
a result, maintenance intervals may vary. Experience is 
a valuable guide in determining the best maintenance 
interval for air brake system components. At a minimum, 
the low pressure indicator should be inspected every 6 
months or 1500 operating hours, whichever comes fi rst, 
for proper operation. Should the low pressure indicator not 
meet the elements of the operational tests noted in this 
document, further investigation and service of the valve 
may be required.

1.  If possible, determine the setting of the low pressure 

indicator by referring to the label on the valve or the 
vehicle manual.

2.  Operation of the low pressure indicator may be checked 

with ignition switch “on” by reducing the system 
pressure and observing that low pressure warning 
occurs when system pressure drops below the setting 
of the low pressure indicator. The contacts will be 
closed when the warning device operates. If the setting 
of the indicator is unknown, the contacts should close 
between approximately 70 psi and 50 psi.

1.   With air pressure present at the supply port, coat the 

indicator with a soap solution. No leakage is permitted.

1.  Block the wheels or secure the vehicle with other than 

service brakes.

2.  The ignition switch should be in the “off” position.

3.  Drain the air from the system.

4.  Disconnect the electrical connections at the low 

pressure indicator.

5.  Disconnect the air line and mounting bolts or unscrew 

the Indicator from the fi tting and remove.

1.  Install in a convenient location for servicing.

2.  Connect to a reservoir pressure line at a high point in 

the system for adequate drainage.

3.  If installing a Bendix

®

 LP-2

™

 indicator, use a supply line 

of 1/4” O.D. minimum.

4.  Connect the Indicator terminals in series with the 

ignition switch and the warning device.

NOTE:  It is generally recommended that the low pressure 

indicator, if faulty, be replaced with a new unit; 
however, service parts are available; and if repairs 
are necessary, the following will apply:

LP-2

™

 indicator. Unscrew the cover retainer from the 

body. Remove cover and remove spring and diaphragm 
assembly.

LP-3

™

 indicator. Remove cover screw and lockwashers. 

Remove the cover, contact disc, spring, and shim(s). (Note: 
shims may or may not be present.) Remove contact plate, 
gasket, piston, and o-ring diaphragm.

1.  Clean all metal parts in mineral spirits and dry them 

completely.

2.  Inspect all parts for excessive wear or deterioration. 

Check the valve spring for cracks or corrosion.

3.  Inspect contact points. If contact points are not severely 

pitted, they can be dressed with a fi ne fi le.

Replace all parts that were discarded and any parts not 
found to be serviceable during inspection, using only 
genuine Bendix replacement parts.

NOTE:  When using pipe thread sealant during assembly 

and installation, take particular care to prevent the 
sealant from entering the valve itself. Apply the 
sealant beginning with the second thread back 
from the end.

1.  Place and position the diaphragm assembly in the 

body. Position the spring so that it rests on the upper 
diaphragm follower.

2.  Place the cover over the diaphragm and screw the 

cover retainer to the body and tighten securely. (Torque 
to 110-130 inch pounds.)