1998 INDEX Sensors & Controls, Inc. All Rights Reserved

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1 ACPU CM-820 APAds ACPU Controller Product Description and Troubleshooting Manual 1998 INDEX Sensors & Controls, Inc. All Rights Reserved The information contained herein is proprietary data, and is not for dissemination or disclosure, in part or in whole, for any purpose other than that for which it is submitted except as authorized in writing by Index Sensors and Controls, Inc. Additions and modifications will be published in future revisions. Index Sensors and Controls, Inc. reserves the right to make changes at any time. This specification conveys no license under any patent, trademark or other right. APAds is a registered trademark of Index Sensors and Controls, Inc. Patent number 5,761,918. PM-003 Rev. D

2 PRODUCT OVERVIEW 2 The CM820 is an electronic, micro-controller based device that implements the functions of the APAds (Air-conditioning Protection And Diagnostic System) control and diagnostic system. It is a member of a family of APAds controller products specifically designed to reduce air conditioning maintenance costs in vehicular HVAC systems by increasing the life of system components and aiding in the diagnosis of system faults. The unit receives input from two pressure switches, a thermostat and numerous parameters read from the vehicular, SAE J1587 compatible data bus. The input signals are interpreted by control laws which derive outputs to the AC clutch coil, fan actuator circuit and diagnostic codes. In the APAds system, the CM820 controller becomes the only device through which power is switched to the AC clutch coil FUNCTION OVERVIEW Typical AC Prob oblems The durability of the compressor and refrigerant hoses is adversely affected by operation of the AC system with reduced (or excessive) refrigerant charge. Operation with a partial charge of refrigerant can cause compressor lubricant starvation, compressor overheating due to rapid cycling, seal failure and can lead to damaged hoses and fittings due to exposure to excessive temperatures. Operation at excessive refrigerant charges can severely stress the entire AC system causing hose and fitting leaks. Low system voltages can cause the compressor clutch to slip and overheat and loose electrical connections can cause erratic compressor cycling which leads to clutch failures. Traditional electrical control systems based upon a series of simple pressure switches are unable to prevent or detect these harmful modes of operation. APAds Ads System The APAds control system is composed of an electronic control module (CM820), two-smart pressure switches and a conventional evaporator thermostat (TSTAT). This system is the first practical step in decades (in the heavy commercial vehicle market) to bring the AC system controls to a new level of sophistication and benefit. With APAds, air conditioning reliability is improved by actively monitoring system conditions and controlling the refrigerant compressor and the on-off fan drive. AC system maintenance is reduced since the control algorithms of APAds do not allow operation in unstable and self destructive modes. Additionally, diagnostics aid technicians in the servicing of systems by communicating specific fault codes that warn of existing or impending problems. The CM820 operates as the main AC system control. The module provides an on/off output to the AC compressor clutch coil and the fan actuator circuit trigger. Both of these outputs are a function of the APAds control laws. Since the CM820 is the controller of the AC compressor clutch coil, it incorporates its own high current (high side, sourcing) drive relay thereby eliminating external relays previously used to engage the AC clutch. The CM820 receives inputs from two smart switches and the evaporator thermostat. Fault diagnostic communication is accomplished through J1587 databus. The CM820 is designed to interface with electronically controlled diesel engines. APAds mitigates problems currently responsible for making the air conditioning system one of the highest maintenance expense items for most heavy commercial vehicle fleets. The APAds system protects AC system components from self destruction by placing limits on the dynamic response of the system under certain environmental and sub-optimal conditions. ACPU CONTROL FUNCTIONS AC Start Delay - Compressor hold-off during engine cranking. This period begins as soon as power is applied to the module and engine RPM is detected. It allows the engine and associated components to stabilize during which time the AC is absolutely held off for 15 seconds. Compressor Lubrication - Lubrication period on every ignition cycle. This period commences after AC start delay and when all system inputs are in a state which permit AC operation. It forces an AC request for 15 seconds regardless of the ATC mode. All fan and AC control laws govern the operation of the system during this period.

3 3 ACPU Product Description and Troubleshooting Cycle Limiting The AC compressor is not allowed to cycle on and off more than once every 15 seconds. T-stat Sensor The AC compressor is not allowed to run if the t-stat sensor detects an evaporator freeze condition. High Pressure Cutout The AC compressor is not allowed to run for an extended period of time if the high pressure switch indicates a high pressure condition. Low Pressure Cutout The AC compressor is not allowed to run if the low pressure switch indicates low pressure. Low Voltage Cutout The AC compressor is not allowed to engage if VIGN is less than 11.0 volts plus the expected clutch current line drop. High Voltage Cutout The AC compressor is not allowed to run if VIGN is greater than 16 volts. Diagnostic Latch Out The AC system is turned off when any of the following diagnostic faults are detected: Low pressure Open clutch circuit Shorted clutch circuit Engine FAN Trigger The module performs adaptive Fan timing control. If the high pressure switch indicates a high pressure condition and ROAD_SPD is less than 5 mph, the FAN is turned on for 180 seconds. If the high pressure switch indicates a high pressure condition and ROAD_SPD is 5 mph or greater but less than 30 mph, the FAN is turned on for 90 seconds. If the high pressure switch indicates a high pressure condition and ROAD_SPD is 30 mph or greater, the FAN is turned on for 45 seconds). If the parking brake is set and ROAD_SPD is zero and the high pressure switch detects a high pressure condition, the FAN is requested until the parking brake is not set or ROAD_SPD is not zero or the TSTAT circuit detects no activity for more than two minutes. (That is, the driver shuts off the AC for more than 2 minutes.) The FAN trigger (and AC clutch) are disengaged when a low air pressure condition is broadcast over the J1587/ J1708 bus.

PINOUT DEFINITION 4 PHYSICAL I/O Table Name Wire Color Wire # Function Description ACDRIVE Dk Blue E output AC Compressor Clutch Coil Drive DATA + Pink A digital I/O Databus positive connection DATA

4 PINOUT DEFINITION 4 PHYSICAL I/O Table Name Wire Color Wire # Function Description ACDRIVE Dk Blue E output AC Compressor Clutch Coil Drive DATA + Pink A digital I/O Databus positive connection DATA - Purple B digital I/O Databus negative connection FAN Orange G output Fan actuator circuit GND Black D power Module ground voltage HPx Yellow Hpx A analog input High Pressure Switch HPx Rtn Yellow/Blk Hpx B signal return High Pressure Switch return LPx White Lpx B analog input Low Pressure Switch LPx Rtn White/Blk Lpx A signal return Low Pressure Switch return TSTAT Green C digital input Evaporator Thermostat and AC on/off input VIGN Red F power Module supply voltage, ignition switched INPUT DESCRIPTIONS The module receives inputs from the following sensors: DATA+ and DATA- Hardware interface to J1587/J1708 vehicular databus. DATA+ in the positive connection to the differential bus. DATAis the negative connection to the differential bus. These signals provide for bi-directional data communications. LPx, Low Pressure Switch, Index PM-700 series: The LPx input is connected to a PM-700 low pressure switch. Located on the suction side of the refrigerant compressor, this smart device has a 2.49Kohm resistor installed in parallel with the electrical contacts to allow diagnosing of sensor wiring and connector faults. This switch circuit is configured to provide a low resistance current path when it closes. The pressure switch contacts are open when the pressure is sufficiently high (above 34 psi nominal). Contacts close when the pressure falls below approximately 10 psi and reopen after the pressure climbs back above 34 psi (nominal). Low pressure switch activity is the primary indicator of a loss of charge and is also used to preclude compressor operation in extremely cold temperatures.

5 5 ACPU Product Description and Troubleshooting HPx, High Pressure Switch, Index PM-700 series : The HPx input is connected to a PM-700 high pressure switch. Located on the discharge side of the refrigerant compressor, this smart device has a 2.49Kohm resistor installed in parallel with the electrical contacts to allow diagnosing of sensor wiring and connector faults. This switch circuit is configured to provide a low resistance current path when it closes. The pressure switch contacts are closed when the pressure is sufficiently low (below 260 psi nominal). Contacts open when the pressure climbs above approximately 300 psi and reclose after the pressure falls back below 260 psi (nominal). The high pressure switch is the primary control for the fan and is used to preclude compressor operation when excessive discharge pressures are present. TSTAT (Evaporator Thermostat): The main AC system on/off switch and the evaporator thermostat are in series and are connected to this input. The series switches are configured to switch to battery voltage to command AC compressor operation. The thermostat contacts close when the temperature is greater than 38º F (nominal). The contacts open when the evaporator temperature drops below approximately 32º F. The thermostat is used to turn off the compressor whenever frost begins to form on the evaporator. OUTPUT DESCRIPTIONS The module produces the following output signals: ACDRIVE (Compressor Clutch Drive) A high side relay switch that provides battery voltage to the AC compressor clutch coil when activated. DATA+ and DATA-(see previous) FAN (Fan Actuator) A low side, sinking (to ground), open drain MOSFET that is used to signal the fan actuator circuit to activate the on-off fan drive. A fan on state is signified by the MOSFET being in the non-conducting state (off). DIAGNOSTICS: Upon detection of system faults, the unit broadcasts diagnostic information over the databus. Fault messages broadcast by ACPU controller are displayed on the dash in the following format. A/C SYST REFRIG PRES HIGH PRESSURE HIGH 190 S A/C SYST REFRIG PRES LOW PRESSURE LOW 190 S A/C SYST LO PRES SW LOW PRESSURE SWITCH OPEN OPEN 190 S A/C SYST CLUTCH CIR OPEN WIRE TO CLUTCH OPEN 190 S A/C SYST CLUTCH CIR SHORTED CLUTCH SHORT 190 S A/C SYST TSTAT CIR ERRATIC T-STAT ERRATIC 190 S A/C SYST BAT VOLTAGE LOW BATTERY VOLTAGE LOW A/C SYST HI PRES SW HIGH PRESSURE SWITCH OPEN OPEN 190 S A/C SYST HI PRES SW HIGH PRESSURE SWITCH LIFE HAS EXCEEDED CALIBRT 190 S ,000 CYCLES

6 6 A fault becomes active when it occurs and it remains active until it is cleared A fault record can be cleared by sending a clear command with the databus tool, such as Service Pro. Clearing a fault permanently erases it from module memory and it will only become active again if the fault reoccurs. Upon occurrence of a fault or warning, a message is repeatedly (every 15 seconds) sent over the databus until it becomes inactive or is cleared. High Pressure The high pressure condition is detected by monitoring high pressure switch activity after the fan has been engaged. This fault can be caused by fan drive failure, condenser blockage, or refrigerant overcharging. If this fault is detected, the AC is held off for the remainder of the ignition cycle. High Pressure Switch Open Indicates that the wiring to the high pressure switch is open circuit. This can be caused by an unseated connector, break in the wiring harness or moisture intrusion into the connectors or switch. When continuity to the switch is remade, this fault becomes inactive. High Voltage Indicates a high supply voltage condition (greater than 16 volts). This can be caused by a defective alternator, voltage regulator or surges on the supply line. The High Voltage warning goes away when the supply voltage returns to normal (below 16 volts). Low Pressure* This is detected by monitoring the ambient temperature and activity of the low pressure switch. Indicative of loss of refrigerant. Low Pressure Switch Open Indicates that the wiring to the low pressure switch is open circuit. This can be caused by an unseated connector, break in the wiring harness or moisture intrusion into the connectors or switch. When continuity to the switch is remade, this fault becomes inactive. Low Voltage Indicates a low supply voltage condition. This can be caused by a defective alternator, discharged batteries or excessive electrical loads. The Low Voltage warning goes away when the supply voltage returns to normal (above 11 volts). Open Clutch If no current is sensed when the AC clutch is engaged, an open connection to the clutch coil is inferred. When continuity to the clutch is remade, this fault becomes inactive. Shorted Clutch Is detected by an excessive current flowing to the compressor clutch. This is indicative of either a shorted clutch coil or shorted wiring to the clutch. If this fault is detected, the AC is held off for the remainder of the ignition cycle. Erratic T-stat. The T-stat input has been detected to be switching on and off at a rapid rate. Indicative of a bad AC on switch, TSTAT, or intermittent connections in the wiring or connectors.

7 7 ACPU Product Description and Troubleshooting High Pressure Switch Calibration. Cycle life of High Pressure Switch has exceeded. Replace switch. TROUBLESHOOTING (When fault message is broadcast) DASH MESSAGE DEFINITION POSSIBLE CAUSE ACTION A/C SYST REFRIG PRES HIGH 190 S A/C SYST REFRIG PRES LOW 190 S High pressure fault. The system is exhibiting abnormal high pressure activity. Low pressure fault. This is detected by monitoring the ambient temperature and switching activity of the low pressure switch. Fan drive failure. Blocked air flow. Refrigerant overcharge. Fan circuit has not been turned on in Engine Control Module Partial or total loss of refrigerant A defective low pressure switch Inspect proper operation of solenoid valve/relay and/or related components. Remove restriction from condenser. Reclaim refrigerant and charge to manufacture recommended specification Disconnect main harness to the ACPU module, if engine fan engages replace module. If engine fan doesn t engage, check fan circuit in ECM, and have ECM programmed to accept ACPU input. Check system for leaks Disconnect the low side pressure switch connector and measure the resistance value of the switch. If the resistance shows 2.49k ohms, switch is operating properly, if resistance shows less than 5 ohms, replace switch. NOTE: This check must be done with the switch installed on the vehicle and the ignition on the off position and proper charge. A/C SYST LO PRES SW OPEN 190 S Open in wiring to low pressure switch. Indicates that the wiring to the low pressure switch is defective. Unseated connector. Break between wiring harness and pressure switch. Moisture intrusion into the connectors or switch. The non use of a pressure switch. Check connectors at the module and the pressure switch for loose pins. With the use of an ohm meter, probe the white and white/black pins of the module harness. Resistance should read 2.49k ohms with switch installed and proper charge. Check seals and inspect wires for hole punches. Install the correct pressure switch.

8 8 TROUBLESHOOTING (When fault message is broadcast) DASH MESSAGE DEFINITION POSSIBLE CAUSE ACTION A/C SYST CLUTCH CIR OPEN 190 S Open wire to A/C clutch. Detected by the inadequate current through the compressor clutch. If no current is sensed when the A/C drive is turned on, an open connection to the clutch coil is indicated. A break in the wiring between the ACPU module and the A/C compressor clutch. Check wiring with an ohm meter for continuity. A/C SYST CLUTCH CIR SHORT 190 S Short wired or A/C clutch. Detected by excessive current through the compressor clutch. This is indicative of either a short clutch coil or shorted wiring to the clutch. With the use of an ohm meter, check the resistance of the clutch coil. If the reading is less than 2.8 ohms, replace clutch. Locate and repair shorted or frayed wiring between the ACPU module and A/C clutch. A/C SYST TSTAT CIR ERRATIC 190 S Erratic evaporator thermostat. The termostat input has been detected to be switching on and off at a rapid rate. An erratic power signal between the A/C cab controls and ACPU module. Check for a bad A/C on switch, thermostat, or an intermittent connection in the wiring or connection between the cab controls and the ACPU module (pin c). A/C SYST BAT VOLT LOW Low system voltage. Indicates a low supply voltage condition, voltage has dropped below 11.0 volts. Possibly caused by a defective alternator, discharged batteries or excessive electrical loads. Check voltage at the control module harness by probing pins D (ground) and F (power). If voltage is less than 11.0 volts start checking for voltage drops. A/C SYST HI PRES SW OPEN 190 S Open in wiring to high pressure switch. Indicates that the wiring to the high pressure switch is defective. Unseated connector. Break between wiring harness and pressure switch. Moisture intrusion into the connectors or switch. The non use of a pressure switch. Check connectors at the module and the pressure switch for loose pins. With the use of an ohm meter, probe the yellow and yellow/ black pins of the module harness. Resistance should read less than 5 ohms. Check seals and inspect wires for continuity. Install the correct pressure switch. A/C SYST HI PRES SW CALIBRT 190 S Cycle life of high pressure switch has exceeded. High pressure switch has exceeded more than 260,000 cycles. Replace with an F/L part number pressure switch.

9 9 ACPU Product Description and Troubleshooting TROUBLESHOOTING (When fault message is NOT broadcast) Situations that could cause the A/C compressor not to engage and not send a dash message: DASH MESSAGE DEFINITION POSSIBLE CAUSE ACTION No dash message. At ignition turn on, with A/C controls set to the on position, compressor is off for 15 seconds, then remains off indefinitely. No voltage going to A/C compressor. Check for a break in the wiring between A/C clutch and the A/C controls. Check for bad A/C on/off control switch. Check for a bad A/C relay. No dash message. At start up, after 15 seconds, compressor clutch doesn t engage but engine fan engages. Defective high pressure switch. Check switch by measuring the resistance value across the leads. If the resistance shows less than 5 ohms, switch is functioning properly. If resistance is greater than 5 ohms, replace switch. No dash message. Compressor on for a short period of time, off for 15 seconds in a repetitive sequence. Blockage in the high side of the system or in the condensor. Partial loss of refrigerant. Repair restriction. Check system for loss of refrigerant. No dash message. Low air message No RPM message. Clutch is engaged, A/C not cooling. A/C compressor not engaging. A/C compressor not engaging. Inoperative blower motor. A/C drive belt is broken, loose or glazed. Heater valve open valve is broken or control is not operating properly. Moisture in system. Air ducts leaking air flow. Loss of charge before detected. System air pressure is less than 60 psi. Engine RPM is less than 300. Check for proper operation of the blower motors. Tighten or replace compressor drive belt. Repair problem with valve or with controller. Check moisture indicator on drier. Replace if necessary. Repair air leak problem. Check with gauge set, repair leak if necessary. Check for low air pressure. Check for low RPM. TO CLEAR FAULT CODES Clear the error code by using a data bus tool such as Service Pro.

1998 INDEX Sensors & Controls, Inc. All Rights Reserved

CM-813 Product Description & Troubleshooting Manual 1998 INDEX Sensors & Controls, Inc. All Rights Reserved The information contained herein is proprietary data, and is not for dissemination or disclosure,