HEATING AND A/C SYSTEM DESCRI... 2007 CIVIC Heating and A/C System Description The air conditioning (A/C) system removes heat from the passenger compartment by transferring heat from the ambient air to the evaporator. The A/C refrigerant expands in the evaporator, and the evaporator becomes very cold and absorbs the heat from the ambient air. The blower fan pushes air across the evaporator where the heat is absorbed, and then it blows the cool air into the passenger compartment. This vehicle uses HFC 134a (R 134a) refrigerant, which does not contain chlorofluorocarbons. Pay attention to the following service items: Use only the recommended polyalkyleneglycol (PAG) refrigerant oil (SP 10) designed for the R 134a A/C compressor. Intermixing the recommended (PAG) refrigerant oil with any other refrigerant oil will result in A/C compressor failure. All A/C system parts (A/C compressor, discharge line, suction line, evaporator, A/C condenser, receiver/dryer, expansion valve, O rings for joints) are designed for refrigerant R 134a. Use a halogen gas leak detector designed for refrigerant R 134a. Use only a recovery/recycling/charging station that is U.L. listed and is certified to meet the requirements of SAE J2788 to service the R 134a air conditioning systems. Always recover refrigerant R 134a with an approved recovery/recycling/charging station before disconnecting http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 1/8
any A/C fitting. Oil Separator Oil emission from the A/C compressor to the A/C line is reduced by placing the oil separator in the A/C compressor. This results in a thinner oil film inside of the heat exchanger (A/C condenser and evaporator). Air conditioning efficiency is increased without sacrificing engine performance. A/C Pressure Sensor The A/C pressure sensor converts A/C pressure into electrical signals to the ECM/PCM. A/C System Pressure* Sensor Output Voltage (V out) System Operation Abnormally low pressure: Below 196 kpa (2.0 kgf/cm2, Below 0.685 V The ECM/PCM disengages the A/C compressor clutch. The radiator and 28 psi) A/C condenser fans operate based http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 2/8
28 psi) A/C condenser fans operate based on engine coolant temperature. Normal operating pressure: Above 196 kpa (2.0 kgf/cm2, 28 psi) Below 1,470 kpa (15.0 kgf/cm2, 213 psi) 0.686 V to 1.944 V The ECM/PCM cycles the A/C compressor clutch based on cooling damaged. The radiator and A/C condenser fans operate at low speed unless the engine coolant temperature exceeds 206 F High operating pressure: Above 1,470 kpa (15.0 kgf/cm2, 213 psi) Below 3,138 kpa (32 kgf/cm2, 455 psi) 1.945 V to 4.575 V The ECM/PCM cycles the A/C compressor clutch based on cooling demand. The radiator and A/C condenser fans operate at high speed. Abnormally high pressure: More than 3,138 kpa (32 kgf/cm2, 455 psi) Above 4.575 V The ECM/PCM disengages the A/C compressor clutch. The radiator and A/C condenser fans operate based on engine coolant temperature. *: The A/C system pressure can be monitored in the HDS PGM FI Data List. The response of the A/C pressure sensor is shown in the graph. NOTE: When the refrigerant is below 196 kpa (2.0 kgf/cm2, 28 psi) or above 3,138 kpa (32 kgf/cm2, 455 psi), the ECM/PCM turns the A/C compressor clutch relay off to protect the A/C compressor. When the refrigerant pressure is above 1,470 kpa (15.0 kgf/cm2, 213 psi), the ECM/PCM switches the radiator and A/C condenser fans to high speed. http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 3/8
Heating/Air Conditioning Door Positions http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 4/8
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HVAC Control Unit Inputs and Outputs Cavity Wire color Terminal name Description Signal 1 BLK S5V Sensor 5 V output about 5.0 V http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 6/8
2 BRN Teva Input for evaporator temperature sensor signal between 1.0 V and 4.0 V depending on evaporator temperature. About 2.5 V at 72 F (22 C). 3 ORN MODE 1 Input for mode motor signal 1 about 5.0 V or about 0 V, depending on mode control 4 LT GRN MODE 2 Input for mode motor signal 2 about 5.0 V or about 0 V, depending on mode control 5 PUR MODE 3 Input for mode motor signal 3 about 5.0 V or about 0 V, depending on mode control 6 BLU MODE 4 Input for mode motor signal 4 about 5.0 V or about 0 V, depending on mode control 7 BLU BLW V Feedback signal of power transistor drain voltage blower OFF: between 5.0 V and 12.0 V. Voltage decreases as blower speed increases 8 YEL BLW G Voltage output of power transistor gate blower OFF: 0 V. Voltage increases as blower speed increases 11 BRN ACS A/C signal output thermal protector has continuity, and A/C request OFF: battery voltage. When A/C request switches ON, voltage changes to about 0 V. 12 RED ILL- Ground for illumination With combination light switch ON: voltage decreases as dash lights brightness increases 13 RED S COM Sensor ground Less then 0.2 V at all times 14 WHT M VENT Drives mode control motor to VENT mode control motor moving to VENT: battery voltage http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 7/8
15 GRN M DEF Drives mode control motor to DEF mode control motor moving to DEF: battery voltage 16 ORN REC Drives recirculation control motor to RECIRCULATE side recirculation control motor in position FRESH: battery voltage 17 PUR FRS Drives recirculation control motor to FRESH side recirculation control motor in position RECIRCU: battery voltage 18 GRY AMD P Detects air mix control air mix door at HOT: about 4.5 V air mix door at COOL: about 0.5 V 19 LT BLU M COOL Drives the air mix control motor to COOL air mix control motor moving to COOL: battery voltage 20 PNK M HOT Drives the air mix control motor to HOT air mix control motor moving to HOT: battery voltage 21 BLK GND Ground for HVAC control unit Less then 0.2 V at all times 22 BRN RrDEF Ry Signal for rear window defogger relay rear window defogger ON: about 0 V rear window defogger OFF: battery voltage 23 LT GRN IG2 IG2 power source battery voltage 24 GRY ILL+ Power source for illumination With Ignition switch ON (II): battery voltage Portions of materials contained herein are sourced from American Honda Motor Inc., Co. Copyright 2009 2013 Service Repair Solutions, Inc. http://dh.identifix.com/searchfixes/index?roid=140601307&vid=2189520&vsm=1&locationid=8#kw=a/c&soption=1&vetid=8&stmode=1&paging=&sm 8/8