Hydraulic ABS (H-ABS) & Hydraulic Power Brake (HPB)

1 Hydraulic ABS (H-ABS) & Hydraulic Power Brake (HPB)Section 2 Contact Customer Care Contact Customer Care 1-888-725-93552- 2-2 Contact Customer Care Contact Customer Care 1-888-725-93552- 2-2 OverviewMeritor WABCO Hydraulic anti -lock Braking System (ABS) is an electronic wheel speed monitoring and control system used on medium-duty trucks, buses and motor home chassis equipped with a Hydraulic Brake Hydraulic ABS WorksABS wheel sensors detect wheel speeds. The sensors generate signals that are transmitted to an Electronic Control Unit (ECU).

2 If the wheels start to lock, the ECU signals the modulator assembly, a control valve as-sembly, to regulate the Brake pressure of each locking an ABS stop, a solenoid valve in the modulator assembly is rapidly pulsed; that is, it opens and closes several times to control the Brake pressure. When this occurs, drivers may notice a pulsating of the Brake pedal. HYDRAULICS ABS (H-ABS)An ABS indicator lamp on the vehicle dash alerts the driver to a possible system fault and provides blink code information to diagnose the :If the ABS indicator lamp comes on during normal vehicle operation, drivers may complete their trip, but are instructed to have their vehicles serviced as soon as the unlikely event of an ABS system malfunction, the ABS in the affected wheel will be disabled and will return to normal braking.

3 The other sensed wheels will retain their ABS LayoutA typical Meritor WABCO D version Hydraulic ABS system with a Cab-Mounted ECU is illustrated Customer Care Contact Customer Care 1-888-725-93552- 2-2 Contact Customer Care Contact Customer Care 1-888-725-93552- 2-2 S446 109 010 0 S446 109 010 7 ECU453 XC3106 S446 044 047 0 S446 044 047 7 ECU451 XC3100 S446 044 061 0 S446 044 061 7 ECU451 XC3101 S446 044 062 0 S446 044 062 7 ECU451 XC3102 D VerSiOn eCUS PArt SerViCe eXCHAnGe COre COre nUmBer nO.

4 GrOUP nO.. S446 044 085 0 S446 044 085 0 ECU452 XC3103 S446 044 086 0 S446 044 086 0 ECU452 XC3104 H-ABS SYStem ComponentS eLeCtrOniC COntrOL UnitS (eCU)C VerSiOn HABSCAB mOUnteD neW SerViCe eXCHAnGe COre COre PArt nO. nO. GrOUP Mounted ECU 12-Volt 4S/4M CAB Mounted ECU 12-Volt 4S/4M12-Volt4S/4M D VerSiOn eCUS PArt SerViCe eXCHAnGe COre COre nUmBer nO. GrOUP nO. Contact Customer Care Contact Customer Care 1-888-725-93552-52-4 Contact Customer Care Contact Customer Care 1-888-725-93552-52-4 rePLAC ement PArtS C VerSiOn HABS mODULAtOr VALVe mODULAtOr ASSy.

5 MODULAtOr BrACket remArkS H-ABS SYStem ComponentS MODULATOR ASSEMBLIES C Version Hydraulic ABS D Version Hydraulic ABS OEM modulator assemblies are sold with dry modulator valves. For aftermarket, Meritor WABCO sells only wet modulator valves (valves pre-filled with Brake fluid). To help you identify the proper replacement parts, we have included the OEM part numbers. OEM Dry modulator valve assemblies are listed WITHOUT the S suffix. NOTE: If the number of the valve you are replacing is for a dry valve, the ArvinMeritor customer service representative will provide the correct WET valve in its place.

6 2 PB-01134 Revised 8-07D VerSiOn HABS mODULAtOr VALVe rePLAC ement PArtS mODULAtOr ASSy. mODULAtOr BrACket remArkS 478 407 014 0 S478 407 015 0 478 407 016 0 S478 407 018 0 S478 407 019 0 S478 407 027 0 S478 407 028 0 478 407 0 0 478 407 061 0 S478 407 062 0 S478 407 056 0 S478 407 056 0 S478 407 056 0 S478 407 060 0 ------------------>S478 407 058 0 ------------------>S478 407 060 0 S478 407 058 0 S478 407 058 0S478 407 56 4 S478 407 56 4 S478 407 58 4 S478 407 57 4 S478 901 52 4 ------------------> S478 407 056 4 ------------------> S478 901 52 4 S478 407 055 2 S478 407 055 2

7 For aftermarket repl. assy. order part no. S478 407 015 0 Two brackets used in this assembly. Replaced by S478 407 062 0 Replaced by S478 407 062 0 For aftermarket repl. assy. order part no. S478 407 018 0 For aftermarket repl. assy. order part no. S478 407 062 0 S478 407 011 0 N/A N/A Valve includes bracket S478 407 012 0 N/A N/A Valve includes bracket S478 407 5 2 Contact Customer Care Contact Customer Care 1-888-725-93552-52-4 Contact Customer Care Contact Customer Care 1-888-725-93552-52-41 Introduction1 Meritor WABCO Maintenance Manual MM-0401 (Issued 12-04)1 IntroductionOverviewMeritor WABCO s Hydraulic Power Brake (HPB)

8 Is a braking and vehicle control system for Business Class trucks, Classes 4through 7, and buses that are equipped with Hydraulic brakes. The HPB system provides the following functions. Full Power Brake performance Brake control functions including anti -Lock Braking System (ABS), Automatic Traction Control (ATC) and Electronic Brake force Distribution (EBD) Optional parking Brake controlSystem ComponentsThe HPB system consists of two main components the Hydraulic Compact Unit (HCU) and a dual circuit master cylinder.

9 The HPB system is also available with an optional parking Brake pressure supply valve. Figure , Figure and Figure Compact UnitThe HCU consists of an electronic control unit, two independent electric motors driving two pump systems, two accumulators, a dual circuit fluid reservoir with integrated filters, pressure relief valves, solenoid valves and a dual circuit relay valve. The HCU is mounted to the vehicle frame rail with two brackets. Figure Two pump motors draw Brake fluid from the reservoir to pressurize the accumulators.

10 The motors are not serviceable. Two gas-filled Hydraulic accumulators store energy supplied by the pumps. Accumulators are sealed at the factory and are non-refillable. Accumulators may be replaced without replacing the entire HCU. The ECU processes sensor signals and generates solenoid valve commands to reduce, maintain or increase Brake pressure for control function. The ECU constantly monitors the pressure in the accumulators, using one pressure sensor per Brake circuit. The ECU may be replaced without replacing the complete HCU.