BENDIX SL-3-SL-4 STOP LIGHT SWITCH User manual

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Bendix®SL-3™& SL-4™Stop Light Switch
SD-06-1800
FIGURE 1 - SL-3™STOP LIGHT SWITCH FIGURE 2 - SL-4™STOP LIGHT SWITCH
DESCRIPTION
The stop light switch is an electro-pneumatic switch and
operatesinconjunctionwiththebrakevalveandstoplights
bycompletingtheelectricalcircuitwhenabrakeapplication
is made.
OPERATION
When a brake application is made, air pressure from the
brake valve enters the cavity below the diaphragm. At
approximately 5 psi, the air pressure underneath the
diaphragm overcomes the force of the spring and moves
thepistonorplungeruntilthecontactpointsclosecompleting
the stop light electrical circuit and lighting the stop lights.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performinganyintrusivemaintenanceprocedures.Awarranty
maybe voided if intrusive maintenance is performedduring
thewarranty period.
No two vehicles operate under identical conditions; as a
result, maintenance intervals may vary. Experience is a
valuableguide indeterminingthebest maintenance interval
for air brake system components.At a minimum, the SL-3™/
SL-4™switch should be inspected every 6 months or 1500
operatinghours, whichevercomesfirst, forproperoperation
andelectricalconnections.ShouldtheSL-3™/SL-4™switch
notmeetthe elements of the operational testsnotedin this
document,furtherinvestigationand serviceofthe valvemay
berequired.
COVER 8
SPRING 11
CONTACT
PISTON
13
BODY
O-RING
DIAPHRAGM 14
CONTACT
STRIP 12
TERMINAL 9 VENT PLUG 10
GASKET
15
MACHINE
SCREWS
7
COVER1
DIAPHRAGM6
BODY
SPRING 3
CONTACTS
TERMINAL 2
PLUNGER 4
TERMINAL
CONNECTOR 7
WASHER5

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TESTING FOR SERVICEABILITY
OPERATING TEST
1. Apply the brake valve and note that the stop light lights
before the delivery pressure reaches 7 psi.
2. Releasethebrakevalveandnotethat thestoplightgoes
“off”.
LEAKAGETEST
1. Withthebrakesfullyapplied,noleakageispermittedat
the stop light switch. If the stop light switch does not
function as described or if leakage is excessive, it is
recommended that it be replaced with a new unit or
repairedwithgenuineBendixpartsavailableatauthorized
Bendix parts outlets.
REMOVING
1. Disconnectelectricalconnectionsatthestop lightswitch.
2. Disconnect air line to the stop light switch.
3. Remove the stop light switch.
INSTALLING
1. Installinaconvenientlocationforservicing.
2. Install with pipe tap pointing to the ground and keep it
high for adequate drainage.
3. Connect the stop light switch in series in the stop light
circuit.
4. Keep the stop light switch terminals away from frame
memberstoavoidgrounding.
5. Connect the pipe tap to the brake chamber supply line
so that the stop light switch will operate whether the
footor hand valve is applied.
DISASSEMBLY
(SL-3™SWITCH)
1. Place hex portion of body in a vise.
2. Using a large end wrench on cover flats, turn cover (1)
in a counterclockwise direction and remove from body.
3. Remove terminal nuts, terminals (2) and terminal
connector (7) from cover.
4. Remove spring (3), plunger (4), washer (5) and
diaphragm(6) from body.
(SL-4™SWITCH)
1. Removetwo machine screws (7)andremovecover (8).
2. Removeterminalnutsandterminals(9)fromcover.
3. Removethevent plug(10)from cover.
4. Remove spring (11), contact strip (12), piston (13) and
o-ringdiaphragm (14) frombody.
CLEANING AND INSPECTION
Cleanallmetalpartsincleaningsolvent.Wiperubberparts
dry with cloth.
Inspect contact points for pits or wear. If pitting is not too
severe, the points may be reconditioned by filing with a
distributorpointfile. If points cannot be reconditioned,they
should be replaced. The contact strip in the SL-4™switch
may be turned over to use the other side of the contacts.
Check the spring for signs of deterioration; Replace if
discolored.ThespringintheSL-3™switchcarries thecurrent
ofthe electrical circuitinvolved;consequently, inthecaseof
excessivecurrent, asmightbe caused byashort, thespring
willbe overheatedandruined.
Inspect cover and body. If cracked or damaged, replace.
Only genuine Bendix service parts should be used for
replacement.
ASSEMBLY
(SL-3™Switch) (Figure 1)
1. Insert terminal screws (2) in cover (1), making sure the
terminal connector (7) is properly positioned.
2. Secure terminal screws with washers and nuts, or
terminal clips, as the case may be.
3. Placediaphragm(6)in body.
4. Position contact plunger (4) on diaphragm.
5. Position spring (3) on plunger.
6. Place washer (5) on diaphragm and screw cover (1)
into body. Torque to 30 foot pounds. Make certain the
ventholein the cover is open.
(SL-4™Switch) (Figure 2)
1. Positionterminals(9)incover(8)andsecurewithwashers
andnutsor terminal clips.Placeventplug(10) in cover.
2. Place o-ring diaphragm (14) and piston (13) in body.
O-ring diaphragm should be installed with its flat side
adjacent to the piston.
3. Place gasket (15) in place on body and contact strip
(12) on piston(13).
4. Position cover assembly on gasket and secure with
machine screws. Torque to 20 inch pounds.
TEST OF REBUILT STOP LIGHT SWITCH
Bothoperatingandleakagetests,asindicatedundersection
headed “Testing for Serviceability”, must be made after
rebuildingor repairing thestoplightswitch. The switchmust
meetthefollowingspecifications;
1. No leakage is permissible at the stop light switch with
thebrakesapplied.
2. Thestop light switch contact should closewithnotmore
than7pounds of air pressure.

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PRECAUTIONARY NOTE:
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
enginebe in operation,EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Useonly the proper toolsand observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems,make certainto drainthe airpressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS®
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures, deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix®replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11. For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lampshould be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.

4BW1593 © 2006 Bendix Commercial Vehicle Systems LLC All rights reserved. 7/2006 Printed in U.S.A.