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®
Air Horns and Valves
SD-06-130
DESCRIPTION
The purpose of our air horn is to provide a warning signal of
greater volume and farther carrying qualities than usually
found on automotive vehicles. The horn is designed on the
principle of a vibrating diaphragm. The horn consists of die
cast bodies, diaphragms, and two chrome plated horn bells,
with the bells in a horizontal position.
Two types of operating valves are commonly used, the
foot-operated horn valve and the hand-operated horn valve.
Each of these valves have a built-in strainer.
OPERATION
The horn is operated by pulling down on the lever of a
hand-operated horn valve or pushing down on the button of
the foot-operated horn valve. This action pushes down on
the supply valve stem in the horn valve and opens the supply
valve.
When the supply valve in the horn valve is opened, air passes
through the horn valve and enters the cavity in the air horn
on one side of the diaphragms. As the air pressure builds up
on the diaphragm, it deflects it and the air escapes through
the horn bells. This action sets up a vibration of the diaphragm
in each horn bell. The two different lengths of horn bells give
the horn its dual tone. The vibrations are set up in an air
column denser than atmosphere, due to escaping
compressed air, which provides unusual tone carrying
qualities.
PREVENTIVE MAINTENANCE
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 air
horns and valves should be inspected every 6 months or
1500 operating hours, whichever comes first, for proper
operation. Should the air horns and valves not meet the
elements of the operational tests noted in this document,
further investigation and service of the valve may be required.
TESTING FOR SERVICEABILITY
OPERATING TEST
1. With air pressure in the system, operate the horn valve
and the horn should give a loud, clear dual tone horn
blast.
LEAKAGE TEST
1. With horn valve in the released position, leakage at the
delivery port or at the valve stem at the top of the horn
valve should not exceed a 1” soap bubble in 5 seconds
(100 SCCM).
2. With the horn valve applied, leakage at the stem at the
top of the horn valve should not exceed a 1” soap bubble
in 5 seconds (100 SCCM).
REMOVING
To remove the air horn or horn valve;
AIR HORN
1. Disconnect the air line to the air horn.
2. Remove air horn mounting nut and remove horn.
HORN VALVE
1. Drain air brake system.
2. Disconnect air lines to the horn valve.
3. Remove mounting bolts and remove horn valve.
INSTALLING
To install an air horn or air horn valve;
AIR HORN
1. Mount horn on top side of vehicle roof or under hood.
2. Securely bolt horn on a flat surface and use care to be
sure the body is not distorted.
3. The horn bells should point down slightly for adequate
draining.
4. Install at least 1/4" O.D. tubing to the air horn.
HORN VALVE
1. Mount the valve in the cab where it can be easily removed
for servicing.
2. Mount so that pull-cord for the hand-operated valve will
be within easy reach of driver.
3. Mount the foot-operated valve on floor in a convenient
location for driver’s left foot.
4. Connect air lines to the horn valve.
