Document 3JRO6ZjeRKjZyyL1D73eRD3aa

I rr i BUUETIh FEBRUARY 22, 1978 i\lo. Q94 under brakes FOR BRANCHES, DISTRIBUTORS AND CUSTOMERS. CHASSIS AFFECTED ALLENTOWNSf HAYWARD OAKVILLE & ANTI-WHEEL LOCK SYSTEM -"Trouble Shooting Prreedure (Bendix MC-1 and MC-2 Systems) PURPOSE To provide service personnel with trouble shooting procedures for this new anti-wheel lock system. RECOMMENDATION Make the information contained in this bulletin available to all who are responsible for brake system service. INFORMATION The Bendix anti-wheel lock system is similar to others in use on Mack vehicles. It consists of an electronic controller with integral warning unit, that modulates a control valve and a wheel speed sensor sys tem. Two systems are available, MC-1 and MC-2. The MC-1 system utilizes one controller for each axle, whereas the MC-2 system has a single controller to monitor two axles. The following trouble shooting guide is offered to facilitate diagnosis and correction of any problems that may develop. See Figure 1 and 2. PlINTtO IN USA. cikculat: 1. 'VEHICLE POWER 2. SOLENOIO 3. SOLENOID 4. 'VEHICLE GROUND 5. SENSOR COMMON 6. RIGHT WHEEL SENSOR 7. LEFT WHEEL SENSOR 8. ELECTRONIC SPEEOO (OPT.) 9. INDICATOR LAMP REVERSED IN A POSITIVE GROUNO SYSTEM FIGURE 1 EC-1 CONTROLLER TERMINAL CONNECTIONS 1. 'VEHICLE POWER 2. SOLENOID 3. SOLENOID 4. 'VEHICLE GROUND 5. INDICATOR LAMP S. LEFT & RIGHT WHEEL SENSOR 7. LEFT WHEEL SENSOR 8. RIGHT WHEEL SENSOR 9. RIGHT WHEEL SENSOR 10. LEFT WHEEL SENSOR 11. LEFT AND RIGHT WHEEL SENSOR 12. ELECTRONIC SPEEDO (OPT.) 'REVERSED IN A POSITIVE GROUND SYSTEM FIGURE 2 EC-2 CONTROLLER TERMINAL CONNECTIONS Service Manager Shop Foreman Nignt Fore: nan Nigiu Foreman Inspector Leaciman Inspector Leadnan Inspector Leadmtin Unit Uvcrhaul Roc:n Shop Office Service Operations, Allentown, Pa. U.S.A. Mack SymRtOm Indicator Lamp Does Not Light BENDIX ANTI-LOCK BRAKING SYSTEM MC-1 and MC-2 TROUBLESHOOTING GUIDE 1 PROBABLE tAUSE TEST AVn REMETYTAT. PRDPEnTTDP 1. Defective Indicator 1. Replace bulb: retest, if problem Lamp bulb not corrected, proceed with proba ble cause "2. 2. Bad Ground * 1. Remove controller cover. Inspect controller ground. Connect test lamp to (+ PWR and - IWR) power terminals. Lamp should light. If light does not light, make sure modulator body is properly grounded. Retest, if problem not corrected pro ceed with probable cause #3. 3. Broken wire from Indicator Lamp to "FAIL" terminal of controller. *1. Short the "FAIL" terminal to -PWR terminal, if Indicator light comes on, proceed to step 4. If light does not come on, wire between the fail termi nal and Indicator light or wiring be tween light and vehicle fuse is open (wire broken, poor connection, etc.). 4. Defective controller 1. While highly unlikely, a defective controller may cause the problem. If source of problem is not discovered elsewhere, replace the controller. Indicator lamp stays on after 2 seconds. 1. Open or shorted speed sensor or sensor wiring. 1. Inspect sensor wires from controller to sensor for damage (frayed or broken wires etc.). Repair as neces sary. Repeat self-check. *2. Remove controller cover. Connect test lamp or voltmeter to +PWR and -PWR terminals. If test lamp does not light or there is less than 9 volts, check fuse and power wires to the con troller. *3. Connect a 12-volt test light or volt meter between the terminals listedfor the system you are testing. MC-1 from #4 (SOL) to #6 (-PWR) MC-2 from 6 (SOL) to #8 (-PWR) 4. If test lamp lights or voltage is more then 9 volts, proceed to 5, if test lamp fails to light, go to probable cause #4. 5. Test sensors as follows. (Note: This procedure must be followed for all sen sors). A. Disconnect sensor wires Test with keyswitch on. B. Connect volt/ohmeter leads across wires for one sensor. --------------------------------------------------- .-----_____ FEBRUARY 22, 1978 No. Q94 under BRAKES (Sheet 2) (Continued) C. If ohm reading is between 250 and 10,000 ohms, sensor wiring is o.k. If ohm reading is less than 250. sensor or sensor wiring is shorted. If ohm read ing is more than 10,000. sensor or sensor wiring is open. Sensor wiring and/or sensor must be re placed. Repeat for each sensor. i j D. Attach leads of volt/ohmeter to one sensor lead and chassis. Re sistance should be 100,000 ohms or greater. If not sensor or sen sor wire is shorted to chassis. Repair/replace as necessary. E. If all sensors and wires check o.k., reconnect all wires. Re peat self-check and proceed to probable cause 2. 2. Faulty lamp relay (Optional on some negative ground vehicles and all posi tive ground. If there is no relay proceed to the next probable cause #3). * 1. Check voltage across relay coil. Volt age must be within two (2) volts of battery voltage. If voltage is not satis factory wire from relay to the -PWR terminal of controller or the relay ground is defective. Repair or re place as necessary. If the voltage is satisfactory proceed to probable cause #3. 3. Fail wire shorted to chassis. * 1. Remove fail wire from FAIL terminal. If the light does not go out, the relay is defective and should be replaced. If the light goes out. the controller is probably defective. Replace wires and repeat self-check. If the light does not go out, replace the controller. 4. Defective solenoid 1. Visually inspect solenoid wires for pos sible open or shorts; repair or replace as necessary. If solenoid wires appear to be o.k. proceed to next step. 2. Remove solenoid wires from solenoid terminals, check solenoid with volt/ ohmeter as follows: A. Solenoid resistance should be 3-5 ohms. (If not, replace solenoid). (Continued Over) I B. Attach one lead of volt/ohmeter to one solenoid wire and one lead of volt/ohmeter to controller case; resistance should be greater than 100,000 ohms. (If not, replace solenoid). If correct, go to proba ble cause #5. SYMPTOM (Continued) Indicator lamp is intermittent PROBABLE CAUSE 5. Defective controller 1. Intermittent power 2. Lamp relay (optional on some negative ground vehicles and all positive ground). 3. Defective lamp relay 4. Defective Controller TEST AND REMEDIAL PROCEDURE 1. Replace sensor wires and/or sole noid wires and perform "self-check" procedure with ignition switch. If light fails to go out after 2 seconds and no air bursts are heard at sole noid exhaust, controller should be replaced. 1. Loose connection or defective wiring between controller +PWR terminal and vehicle fuse box. 2. Intermittent or poor ground between controller and chassis 3. Loose connection or shorted wire from fail lamp to "FAIL" terminal of controller. 1. Loose connection or defective wire between controller PWR terminal and lamp relay. Repair as necessary, 1. With 12v across relay the contacts should be open and the indicator lamp off. If different from this, replace relay. 1. While highly unlikely, a defective con troller may cause the problem. If source of problem is not discovered elsewhere, replace controller.