Bendix Commercial Vehicle Systems DS-2 User Manual

Bendix® SL-5™ Stop Light Switch & Bendix® DS-2™ Combined Stop Light Switch & Double Check Valve
SD-06-1804
LEAF
SPRING
FULCRUM
CONTACT
STRIP
DS-2
VALVE
INLET PORT
FIGURE 1 - DS-2™ COMBINED STOP LIGHT SWITCH & DOUBLE CHECK V ALVE SECTIONAL
SHORTING
BAR
OUTLET PORT
DESCRIPTION
TERMINAL
RIVET
PISTON
DIAPHRAGM
SHUTTLE
(CHECK
VALVE)
The stoplight switch is not a serviceable item; and if found defective in either device, the complete unit must be replaced.
The Bendix® SL-5™ stop light switch is an electro-pneumatic 5 psi non-grounded switch that operates in conjunction with the brake valve and stop lights by completing the electrical circuit and lighting the stop lights when a brake application is made.
The shuttle valve in the DS-2™ valve is serviceable and may be replaced.
Both the SL-5™ switch and the DS-2™ valve have been tested and meet the requirements of FMVSS 121.
The DS-2™ combined stop light switch and double check valve, as the name implies, combines a SL-5™ stop light switch with a DC-4™ double check valve to perform the function of both. It operates in conjunction with the brake
OPERATION
The stop switch mechanism is identical in the SL-5™ switch and the DS-2™ valve.
valve and hand control valve by directing the flow of air from whichever delivers the higher pressure into a common delivery line and to the stop light switch, closing the electrical circuit to the stop lamps.
When a brake application is made, air pressure from the brake valve enters the cavity below the diaphragm. The air pressure below the diaphragm moves the piston until it contacts the leaf spring. The leaf spring travels past a fulcrum
The stop light switch can be used with either 12 or 24 volt systems.
at which point the leaf springs snaps a shorting bar which mates with the contact strips. The stop light electrical circuit
VALVE
INLET PORT
SL-5 STOP
LIGHT
SWITCH
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is completed, lighting the stop lights before the brake application pressures reach 6 psi.
The snap action spring design minimizes arcing. The double check valve is activated by air being introduced
through either of the two (2) inlet ports. The greater pressure pushes the shuttle along its guides and closes the opposite inlet port. The air is then directed out the common delivery line and to the stop light switch.
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 DS-2™/SL-5™ valve should be inspected every 6 months or 1500 operating hours, whichever comes first, for proper operation and electrical connections. Should the DS-2™/ SL-5™ valve not meet the elements of the operational tests noted in this document, further investigation and service of the valve may be required.
OPERATING AND LEAKAGE TEST
1. Install an accurate air gauge in the service line (or brake chamber). Apply brake valve gradually . S top lamps should light at 6 psi or less and go out after the brake application is released. This checks the electrical function of the stop light switch in either the SL-5™ switch or DS-2 valve.
2. (DS-2™ valve only) Apply the foot valve and coat the exhaust port of the hand valve (or other alternate source). Reverse the above, applying the hand valve or other alternate source and coat the exhaust port of the foot valve. In either mode a leakage of not more than a 1” bubble in 5 seconds is permissible.
3. (SL-5™ switch or DS-2™ valve) When pressurized, no leakage is permitted from the body of the valve or switch.
If the SL-5™ switch or DS-2™ valve does not function as described above or if leakage is excessive, the valve or switch should be replaced with a new unit or in the case of the double check portion of the DS-2™ valve repaired with genuine Bendix parts.
REMOVING AND INSTALLING
REMOVING
1. Block vehicle wheels or hold by means other than vehicle service brakes.
2. Disconnect electrical connections from terminal screws.
3. (SL-5™ switch) Remove the switch using a wrench on the hex portion of the body .
4. (DS-2™ valve) Disconnect air lines and remove the DS-2 valve.
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INSTALLING
1. Replace the SL-5™ switch or DS-2™ valve in the port from which it was removed. Do not install with the terminals pointing down.
2. Secure electrical connections.
3. Reinstall air line connections to DS-2™ valve.
DISASSEMBL Y (Double Check V alve)
1. Remove three cap screws and cap.
2. Remove o-ring seal from cap.
3. Remove shuttle valve.
CLEANING AND INSPECTION
1. Blow dust or other foreign material out of body . Do not immerse in cleaning fluid.
2. Inspect shuttle valve and o-rings for excessive wear or deterioration. Inspect valve seats for nicks or burrs.
Replace all parts that were discarded and any parts not founds to be serviceable during inspection, using only genuine Bendix replacement parts.
ASSEMBL Y
Before assembling the DS-2™ double check valve, lubricate all o-rings and o-ring grooves with Bendix silicone lubricant (Pc. No. 291 126) or equivalent.
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.
TEST
Repeat “Operating and Leakage T est”.
WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR 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 engine be 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. Use only the proper tools and 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 certain to drain the air pressure 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 recommended procedures, 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 lamp shoud be ON) prior to performing any vehicle maintenance where one or more wheels on a drive axle are lifted off the ground and moving.
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BW1594 © 2006 Bendix Commercial Vehicle Systems LLC All rights reserved. 7/2006 Printed in U.S.A.
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