User manual BENDIX M32 M32QR ANTILOCK MODULATOR ASSY

[. . . ] The supply, delivery and exhaust ports on the M-32TM modulator are identified with a cast, embossed numeral for positive identification. Identification Air Line Connection 1, SUP Supply (incoming air from foot, relay or quick release valve) 2, DEL Delivery (air delivery to service actuators) 3, EXH Exhaust SD-13-4870 1 Front Axle Systems Wheel Control Service Brake Chamber To Antilock Controller M-32QR TM Modulator To Antilock Controller M-32 TM or M-32QRTM Modulator To Antilock Controller Wheel Control Axle Control Rear Axle System Wheel Control To Antilock Controller M-32TM or M-32QRTM Modulator or or Controller/Relay Assembly M-32TM or M-32QR TM Modulator To Antilock Controller M-32TM or M-32QRTM Modulator Quick Release Valve M-32QR Modulator TM To Antilock Controller Service Brake Chamber M-32TM or M-32QRTM Modulator To Antilock Controller Quick Release Valve Service Brake Chamber Service Brake Chamber Service & Spring Brake Chamber FIGURE 3: TYPICAL WHEEL AND AXLE CONTROL SYSTEMS NOTE: use of a quick release valve is not typically required with the M-32QRTM modulator. Refer to vehicle specifications for recommended configuration. FUNCTIONAL CHECK A wiring harness connects the vehicle modulators to the controller. The ABS controller is able to simultaneously and independently control the individual modulators. [. . . ] In the case of an ABS braking system, the driver does not need to "pump the brakes" since the antilock controller is able to apply and release the brakes using the modulators, with far greater speed and accuracy. Depending on the number of modulators used, some systems are able to apply braking power to wheels independently (see page 2). ANTILOCK EXHAUST (Figure 8) When wheel lock is detected or imminent, the antilock controller energizes the supply and exhaust solenoids in the modulator. Energizing the supply solenoid allows application air to flow to the control side of the supply diaphragm. Air pressure acting on the supply diaphragm, along with the spring force, enables the diaphragm to prevent further delivery of air to the brake chamber. Energizing the exhaust solenoid shuts off the air normally applied to the control side of the exhaust diaphragm to keep it closed. Air pressure acting on the exhaust diaphragm, overcomes the spring force, and allows air to exhaust through the exhaust port. ANTILOCK OPERATION GENERAL If a service brake application is made and the antilock system detects an impending wheel lockup, the antilock controller will make a controlled brake application using the modulator. In order to control the brake application, the coils of the two solenoid valves contained in the modulator are energized or de-energized in a preprogrammed sequence by the antilock controller. When a solenoid coil is energized, and depending whether the exhaust or hold solenoid is energized, it either 4 ANTILOCK HOLD MODE (Figure 9) The antilock controller will place the modulator in the Hold position when it senses that the correct wheel speed (braking force) has been attained. The antilock controller will also Brake Valve Supply Port Delivery Port Brake Valve Brake Chamber Supply Port Bias Valve Delivery Port Supply or Hold Diaphragm Closed Spring Exhaust Valve Open Solenoid Energized: Exhaust Moves to Down Diaphragm Position Brake Chamber Supply or Hold Diaphragm Spring Exhaust Valve Solenoid Energized: Moves to Exhaust Down Port Position M-32TM Modulator Solenoid Energized: Moves to Down Position Exhaust Port Solenoid Energized: Moves to Exhaust Down Diaphragm Position M-32QRTM Modulator FIGURE 8: M-32TM MODULATOR ANTILOCK EXHAUST OF BRAKES Brake Valve Supply Port Delivery Port Brake Valve Brake Chamber Supply Port Bias Valve Delivery Port Supply or Hold Diaphragm Closed Spring Exhaust Valve Closed Brake Chamber Supply or Hold Diaphragm Spring Exhaust Valve Solenoid Energized: Exhaust Moves to Port Down Position Exhaust Diaphragm Solenoid Returns to Up Position M-32TM Modulator Solenoid Energized: Moves to Exhaust Down Position Port Exhaust Diaphragm Solenoid Returns to Up Position M-32QRTM Modulator FIGURE 9: M-32TM AND M-32QRTM MODULATORS ANTILOCK APPLICATION HELD POSITION place the modulator in the hold position, prior to entering the reapply mode, when it detects recovery from a locked wheel condition. In this mode of operation, the modulator supply/hold solenoid remains energized while the exhaust solenoid returns to its normal position. The exhaust solenoid allows application air to flow to the control side of the exhaust diaphragm, which then seals the exhaust passage. With the exhaust diaphragm seated, further exhaust of brake chamber air pressure is prevented. Because the supply solenoid remains energized, the supply diaphragm remains seated, thus preventing application air from flowing to the delivery port and out to the brake chamber. After determining the pressure loss with the brakes released (2 PSI/minute allowed), make and hold a full service brake application. Begin timing pressure loss for two minutes while watching the dash gauges for a pressure drop. The leakage rate for the service reservoirs should not exceed 3 PSI/ minute. If either circuit exceeds the recommended two PSI/ minute, apply soap solution to the exhaust port of the modulator and any other components in the respective circuit. The leakage at the exhaust port of most Bendix components, including M-32TM modulators, should not exceed a one-inch bubble in three seconds. If leakage at the modulator is determined to exceed the maximum limits, replace the modulator. ELECTRICAL TESTS 1. Before testing the solenoid assembly of a suspect modulator, its location on the vehicle should be confirmed using the Trouble Shooting or Start Up procedure for the specific antilock controller in use. (See the Service Data Sheet for the antilock controller for this procedure. ) 2. Proceed to the modulator in question and inspect its wiring connector. [. . . ] 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. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition. For vehicles with Antilock Traction Control (ATC), the ATC function must be disabled (ATC indicator lamp should be ON) prior to performing any vehicle maintenance where one or more wheels on a drive axle are lifted off the ground and moving. MODULATOR REMOVAL 1. [. . . ]