Subaru Loyale and Justy A/C Belt Protection System
X 1,000 RPM Compressor RPM Lock Detection Range 6 Engine RPM X 1,000 RPM 7

Normal RPM

20 - 25%
Customer complaints of No A/C after driving for several miles or A/C cools intermittently may be caused by problems with the belt protection system found on Subaru Loyale and Justy models. These problems may also be caused by an incorrectly tensioned A/C accessory belt. There is a great deal of comfusion surrounding this system, mostly due to a lack of reliable information. In this short article, well give you a brief overview of the system and explain what it does. For more in-depth diagnostic information on the Belt Protection System, refer to the appropriate model year Subaru Service Manual. What Does It Do? The Loyale and Justy belt protection system exists to prevent damage to the air conditioning compressor drive belt and to other engine compartment components that could be damaged by a loose or broken belt. The first chart depicts the normal RPM ratio between the Hitachi compressor and the engine. When the system senses a drop in the compressor RPM to engine RPM ratio of more than 20-25 percent (the lock detection range), the system disengages the compressor clutch. In the Matsushita system, the range is 27-37 percent. The pulser monitors the RPM of the compressor and provides a signal to the pulser amplifier, which receives a signal from the ignition coil to detect engine RPM. When the ratio of the compressor RPM to the engine RPM drops below a specified range, the pulser amplifier sends a signal to the air conditioner relay, which disengages the clutch. Once the system detects a locked compressor, the A/C compressors magnetic clutch will remain disengaged or off until the air conditioner switch is turned to the OFF and ON positions again. Refer to the schematics on this page to review the operation and differences between the Hitachi and the Matsushita belt protection systems. Belt Tension Proper belt tension is essential on Loyale and Justy vehicles to ensure proper operation of the air conditioning compressor and related components and to extend belt life. Because the drive belts on some Loyale and Justy vehicles have significantly less contact with the circumference of the compressor pulley (reduced pulley wrap), when compared to earlier models, the drive belt tension has been significantly increased. Proper belt tension prevents damage to the compressor, drive belt, and other engine components. A loose belt can cause noise and slow compressor operation, which causes disengagement of the belt protection system, and decreased belt life. An over-tight belt can increase wear of the compressor bearings, engine component bearings, and can decrease belt life. To maintain the delicate balance between an A/C belt that is too tight and one that is too loose, refer to the appropriate model year Subaru Service Manual for correct belt tension specifications and procedures.

Belt Protection System

Ignition compressor A/C Relay
Battery Blower Relay Thermostat

To Blower switch

Blower (Open at mode Motor Pulser (to detect compressor RPM)
switch off) Pulse Amplifier MT Trinary Switch

Microswitch K/D relay

Engine Coil (to detect engine RPM)
IG SW A/C Cut Unit (AT only)
Hitachi Belt Protection System

Battery Blower Relay

switch off) Pulse Amplifier
Trinary Thermal Switch Protector MT

End Wrench

Thermostat IG SW A/C Cut Unit (AT only)
Matsushita Belt Protection System
For proper operation, Pulser clearance must be adjusted to 3 1mm.
Terminal No. Wire Color Destination

Power Supply

Description
Supplies current to the pulser amplifier through the air conditioner switch and trinary (low pressure) switch for the purpose of activating accessories. Transmits engine RPM to the pulser amplifier in pulse form. Transmits compressor RPM to the pulser amplifier for comparison of ignition pulses.

RY (MT)

Subaru Loyale A/C Pulser Amplifier

RB (AT)

Ignition Coil (-)

Pulse Sensor (-)

Pulse Sensor (+)
When compressor RPM drops below 75-80 percent of engine RPM, the RGs grounding circuit will open. When the thermostat activates to close the ground circuit with the air conditioner switch ON, the clutch will engage. When the compressor is locked, the thermostat activates to open the ground circuit, disengaging the clutch. The thermostat opens and closes the ground circuit, depending on the temperature of the evaporator.
Magnetic Clutch Drive Relay Coil

Ground

BEN-YA INDUSTRIAL CO., LTD.
4F, NO.16, LANE 181, SEC.2, JIUZONG ROAD TAIPEI, TAIWAN, R.O.C. P.O. BOX 48-127 TEL: 886-2-27990822 FAX: 886-2-27978753 E-MAIL: benya@ms24.hinet.net

Catalogue

ITEM NO. SB061BK-BDP0A SB061BK-BDP0B SB061BK-BDP1A SB061BK-BDP1B SB061BK-BDP2A SB061BK-BDP2B SB061BK-BDP3A SB061BK-BDP3B SB061BK-BDP4A SB061BK-BDP4B SB061BK-SU3B SB061BK-SU600 SB061BK-SU6B SB061BK-SU6B0 SB061BK-TBE0 SB061BK-TBE1 SB061BK-TRE0 SB061BK-TRE1 SB116BK-BDP0A SB116BK-BDP0B SB220BK-TBE0 SB237BK-EB10 SB237BK-EB30 SB447BK-EB10 SB447BK-EB20A SB447BK-EB30 SB447BK-EB40A SB830BK-GT40 SB877BK-BDP0A SB877BK-BDP0B SB877BK-BDP1A SB877BK-BDP1B SB877BK-BS1J SB933BK-BDP0A SB933BK-BDP0B SB933BK-BDP1A SB933BK-BDP1B SB933BK-BDP2A SB933BK-BDP2B OEM NO.
PRINTING DATE:2010/1/4 PAGE: 1
DESCRIPTION SUBARU LEONE A22 BRAKE PADS ASBESTOS SUBARU LEONE BRAKE PADS NON-ASBESTOS SUBARU LEONE AA3 BRAKE PADS ASBESTOS SUBARU LEONE BRAKE PADS NON-ASBESTOS SUBARU LEONE A33 BRAKE PADS ASBESTOS SUBARU LEONE BRAKE PADS NON-ASBESTOS SUBARU LEONE AA4 BRAKE PADS ASBESTOS SUBARU LEONE AA4 BRAKE PADS NO ASBESTOS SUBARU NEW LEONE BRAKE PADS ASBESTOS SUBARU NEWLEONE B/PADS NO ASBESTOS SUBARU LEONE AB2 BALL JOINT LOWER R/L SUBARU LEONE AA2,AA4 RACK END R/L SUBARU LEONE AB2,AB4 RACK END R/L SUBARU LEONE AA2,AA4 RACK END R/L SUBARU LEONE 1.8 TURBO TIMING BELT SUBARU LEONE 1.8 TURBO TIMING BELT SUBARU LEONE AB2 TIE ROD END OUT R SUBARU LEONE AB2 TIE ROD END OUT L SUBARU FF1 SUPER BRAKE PADS ASBESTOS SUBARU FF1SUPER BRAKE PADS NO ASBESTOS SUBARU IMPREZA/LEGACY 1.6, 1.8 TIMING BELT SUBARU EJ15,16,18,22, 22T MAIN BEARING STD SUBARU EJ18, EJ22, EJ25 C/ROD BEARING STD SUBARU EJ15/EJ16/EJ20/EJ25 (16V) MAIN BEARING STD SUBARU EJ15/EJ16/EJ20/EJ25 (16V) MAIN BEARING 0.25 SUBARU EJ15/EJ16/EJ20/EJ25 (16V)CON ROD BEARING STD SUBARU EJ15/EJ16/EJ20/EJ25 (16V)CON ROD BEARING 0.25 SUBARU EA82 (AA7,AL7) GASKET SET SUBARU JUSTY KA7 BRAKE PADS ASBESTOS SUBARU JUSTY KA7 BRAKE PADS NO ASBESTOS SUBARU JUSTY KA5 BRAKE PADS ASBESTOS SUBARU JUSTY KA5 BRAKE PADS NO ASBESTOS SUBARU JUSTY KA7/KA8 BRAKE SHOES REAR SUBARU REX COMBI BRAKE PADS ASBESTOS SUBARU REXCOMBI BRAKE PADS NO ASBESTOS SUBARU LEGACY BC BRAKE PADS ASBESTOS SUBARU LEGACY BRAKE PADS NON-ASBESTOS SUBARU VIVIO KK3 BRAKE PADS ASBESTOS SUBARU VIVIO KK3 BRAKE PADS NON ASBESTOS
ITEM NO. SB933BK-BDP3A SB933BK-BDP3B SB933BK-BDP4A SB933BK-BDP4B SB933BK-BDP5A SB933BK-BDP5B SB933BK-BDP6A SB933BK-BDP6B SB933BK-EB10 SB933BK-EB30 SB933BK-TBE0 SB933BK-TBE1 SB933BK-TSB0 SB933BK-TSB1 SB933BK-TSB2 SB933BK-TSB3 SB951BK-TBE0 SB951BK-TBE1 SBC-1617 SBC-1627 OEM NO.
PRINTING DATE:2010/1/4 PAGE: 2
DESCRIPTION SUBARU SAMBAR BRAKE PADS ASBESTOS SUBARU SAMBAR BRAKE PADS NON ASBESTOS SUBARU LEGACY BD4 BRAKE PADS ASBESTOS SUBARU LEGACY BRAKE PADS NON-ASBESTOS SUBARU IMPREZA GC3 BRAKE PADS ASBESTOS SUBARU IMPREZA BRAKE PADS NON-ASBESTOS SUBARU LEGACY BG4 BRAKE PADS ASBESTOS SUBARU LEGACY BRAKE PADS NON-ASBESTOS SUBARU VIVIO (EN07) 658c.c MAIN BEARING STD SUBARU VIVIO (EN07) 658c.c CON ROD BEARING STD SUBARU IMPREZA/FORESTER 2.5L 16V TIMING BELT SUBARU IMPREZA, LEGACY 2.0L TIMING BELT SUBARU IMPREZA TENSIONER BEARING SUBARU IMPREZA TENSIONER BEARING SUBARU IMPREZA TENSIONER BEARING SUBARU IMPREZA/LEGACY (EJ20/EJ16) TENSIONER BEARING PULLEY ONLY SUBARU XT/XT6 2.7L (RIGHT)TIMING BELT SUBARU XT/XT6 2.7L (LEFT) TIMING BELT GALVANISED STRANDED WIRES 2.5MM 1X19 GALVANISED STRANDED WIRE 3MM 1X19